scientificamerican--2020-09-29--Millions of Rapid COVID-19 Antigen Tests May Help Fill the Testing Gap

20 ) : This story has been updated and republished in light of announced plans to ship millions of antigen tests to states and vulnerable co An inexpensive coronavirus test that millions of Americans could use at a pharmacy , in a workplace or even at home could prove to be a vital asset in allowing people to return to jobs and school .
Deborah Birx , the White House ’ s coronavirus-response coordinator , has called rapid antigen tests the “ breakthrough innovation ” that is needed to perform hundreds of millions of such assays a day .
The @ @ @ @ @ @ @ tests might be used to examine broad swaths of the public .
The technique often involves a technology—called a lateral flow assay—similar to that employed in home pregnancy tests .
In the test , an antibody can bind to one of the spike proteins ( the antigens ) that cover the surface of the virus like the spines on a puffer fish .
The tests are inexpensive to produce and simple to use , and they deliver results in minutes .
On September 28 , several months after this story was originally published @ @ @ @ @ @ @ to distribute 150 million of these assays , developed by Abbott Laboratories .
The test , called BinaxNOW , correctly identifies 97.1 percent of positive cases and 98.5 percent of negative cases , and it provides results in 15 minutes .
An Abbott spokesperson declined to comment on the record about the test ’ s accuracy .
The goal is also to field a test that is just as accurate as the current standard , which uses polymerase chain reaction ( PCR ) to process the virus ’ s genetic material and amplify @ @ @ @ @ @ @ hurdles still remain .
“ What you would want in terms of a breakthrough is that [ an antigen ] test is more sensitive , [ or less prone to false negatives ] , and easier to use than a PCR-based test .
And that is not so easy to do , ” says Bettina Fries , chief of the infectious diseases division at Stony Brook Medicine .
“ Normally , PCR-based tests are more sensitive.
” The urgent need to conduct massive levels of testing means that any feasible technology is being @ @ @ @ @ @ @ device company in Bethlehem , Pa. , received a $ 710,310 federal contract last month for an in-home assay that can potentially detect a coronavirus antigen in saliva in as little as 20 minutes .
Stephen Tang , the company ’ s CEO , says such antigen tests are needed to screen millions of people per day .
“ You can ’ t be dependent on the throughput of laboratories and the availability of medical and laboratory professionals , ” as PCR assays typically require , to conduct widespread testing , he says @ @ @ @ @ @ @ of copies of its target RNA , it is able to detect a virus at far lower concentrations , called the limit of detection , than antigen tests typically can .
PCR ’ s limits of detection “ are on the order of a few hundred virus particles in a milliliter of transport liquid , ” says Geoffrey Baird , acting chair of laboratory medicine at the University of Washington ’ s School of Medicine .
In contrast , the sensitivities of rapid antigen tests have been mixed .
A 2016 analysis of @ @ @ @ @ @ @ cause strep throat , for example , found they had a sensitivity of 86 percent on average—turning in false negative results for 14 percent of people with strep .
Antigen tests used to diagnose viral infections such as the flu are even less sensitive , often reporting a negative result when the virus is actually present .
Their specificity , or ability to correctly avoid false positive results , is often much higher .
They can exceed 95 percent , meaning less than 5 percent of people without infection would test positive .
@ @ @ @ @ @ @ be used as first-pass screening tools that would be confirmed with follow-up PCR assays .
Otto Yang , an infectious disease researcher at the University of California , Los Angeles , is uncertain if that goal can be achieved .
“ Generally , when you ’ re doing it that way , you aim for higher sensitivity and less specificity in your screening test , ” he says .
“ It only makes sense if you ’ re trying to save money or reagents , and you don ’ t have the capacity @ @ @ @ @ @ @ only potential benefit would be cost savings , but the loss of sensitivity is a big problem.
” The approach would make sense , Yang adds , only if the first-pass screening test was at least as sensitive as PCR in addition to being cheaper .
His view will by no means close the debate on the validity of antigen testing .
Lee Gehrke , a microbiologist at the Massachusetts Institute of Technology who co-founded E25Bio , another company developing a coronavirus antigen assay , balks at comparisons of such tests ’ accuracy @ @ @ @ @ @ @ use of the test needs to be tailored to the setting , ” he says .
“ In back-to-work , back-to-school settings , repeated , regular testing is going to be needed .
If the testing is repeated , I believe the rapid [ antigen ] test will pick [ the virus ] up.
” Gehrke acknowledges that infected individuals can have viral proteins present at levels below the test ’ s limit of detection in the first few days of infection .
He says those levels will increase as the infection progresses @ @ @ @ @ @ @ possible that at the very left end of that bell curve , there ’ s a time that PCR can detect [ the virus ] but the rapid antigen test doesn ’ t , ” Gehrke says .
But if the goal of testing is to get people back to work , he adds , a test that has “ less than perfect ” sensitivity will be acceptable if it is also inexpensive .
Yang counters that antigen tests could find a place as a diagnostic tool , yet the results they provide @ @ @ @ @ @ @ much needed early warning signal .
“ If your goal is to detect somebody that has a virus that may be more contagious [ with a greater volume of the pathogen ] , then maybe that does make sense , ” he says .
But if the objective of a periodic antigen test is to detect people early in infection , “ there will be less virus , and so sensitivity will be a big issue.
” The acute need for this type of testing , however , will continue to provide momentum @ @ @ @ @ @ @ Rapid tests are going to miss people who are sick , but they are still very valuable , because they take just a few minutes to test somebody , ” says Gigi Gronvall , an immunologist at the Johns Hopkins Center for Health Security .
“ If we ’ re able to scale up PCR , that will give you a more accurate , sensitive result .
But there is some value at the point of care to having a screen like this.
” Ultimately , these debates may be put to rest @ @ @ @ @ @ @ testing broadly is clearly something that we need to contain the epidemic .
But all of this is a stopgap , ” says Karla Satchell , a microbiologist at the Northwestern University Feinberg School of Medicine .
“ What we really need is a vaccine.
” Read more about the coronavirus outbreak from Scientific American here , and read coverage from our international network of magazines here .

Editor's Note (9/29/ 20): This story has been updated and republished in light of the Trump administration’s newly announced plans to ship millions of antigen tests to states and vulnerable co mmunities.
An inexpensive coronavirus test that millions of Americans could use at a pharmacy, in a workplace or even at home could prove to be a vital asset in allowing people to return to jobs and school. Deborah Birx, the White House’s coronavirus-response coordinator, has called rapid antigen tests the “breakthrough innovation” that is needed to perform hundreds of millions of such assays a day. The remarks echoed her previous statements that antigen tests might be used to examine broad swaths of the public.
The technique often involves a technology—called a lateral flow assay—similar to that employed in home pregnancy tests. In the test, an antibody can bind to one of the spike proteins (the antigens) that cover the surface of the virus like the spines on a puffer fish. The tests are inexpensive to produce and simple to use, and they deliver results in minutes. On September 28, several months after this story was originally published, the Trump administration announced a plan to distribute 150 million of these assays, developed by Abbott Laboratories. The test, called BinaxNOW, correctly identifies 97.1 percent of positive cases and 98.5 percent of negative cases, and it provides results in 15 minutes. An Abbott spokesperson declined to comment on the record about the test’s accuracy.
The goal is also to field a test that is just as accurate as the current standard, which uses polymerase chain reaction (PCR) to process the virus’s genetic material and amplify it for detection. But major technical hurdles still remain. “What you would want in terms of a breakthrough is that [an antigen] test is more sensitive, [or less prone to false negatives], and easier to use than a PCR-based test. And that is not so easy to do,” says Bettina Fries, chief of the infectious diseases division at Stony Brook Medicine. “Normally, PCR-based tests are more sensitive.”
The urgent need to conduct massive levels of testing means that any feasible technology is being considered. OraSure Technologies, a medical device company in Bethlehem, Pa., received a $710,310 federal contract last month for an in-home assay that can potentially detect a coronavirus antigen in saliva in as little as 20 minutes. Stephen Tang, the company’s CEO, says such antigen tests are needed to screen millions of people per day. “You can’t be dependent on the throughput of laboratories and the availability of medical and laboratory professionals,” as PCR assays typically require, to conduct widespread testing, he says.
Because a PCR test makes thousands of copies of its target RNA, it is able to detect a virus at far lower concentrations, called the limit of detection, than antigen tests typically can. PCR’s limits of detection “are on the order of a few hundred virus particles in a milliliter of transport liquid,” says Geoffrey Baird, acting chair of laboratory medicine at the University of Washington’s School of Medicine.
In contrast, the sensitivities of rapid antigen tests have been mixed. A 2016 analysis of 116 such tests for the bacteria that cause strep throat, for example, found they had a sensitivity of 86 percent on average—turning in false negative results for 14 percent of people with strep. Antigen tests used to diagnose viral infections such as the flu are even less sensitive, often reporting a negative result when the virus is actually present. Their specificity, or ability to correctly avoid false positive results, is often much higher. They can exceed 95 percent, meaning less than 5 percent of people without infection would test positive.
Birx had said that antigen tests could be used as first-pass screening tools that would be confirmed with follow-up PCR assays. Otto Yang, an infectious disease researcher at the University of California, Los Angeles, is uncertain if that goal can be achieved. “Generally, when you’re doing it that way, you aim for higher sensitivity and less specificity in your screening test,” he says. “It only makes sense if you’re trying to save money or reagents, and you don’t have the capacity [to do PCR]. The only potential benefit would be cost savings, but the loss of sensitivity is a big problem.” The approach would make sense, Yang adds, only if the first-pass screening test was at least as sensitive as PCR in addition to being cheaper.
His view will by no means close the debate on the validity of antigen testing. Lee Gehrke, a microbiologist at the Massachusetts Institute of Technology who co-founded E25Bio, another company developing a coronavirus antigen assay, balks at comparisons of such tests’ accuracy with that of PCR. “The use of the test needs to be tailored to the setting,” he says. “In back-to-work, back-to-school settings, repeated, regular testing is going to be needed. If the testing is repeated, I believe the rapid [antigen] test will pick [the virus] up.”
Gehrke acknowledges that infected individuals can have viral proteins present at levels below the test’s limit of detection in the first few days of infection. He says those levels will increase as the infection progresses, however. “It’s possible that at the very left end of that bell curve, there’s a time that PCR can detect [the virus] but the rapid antigen test doesn’t,” Gehrke says. But if the goal of testing is to get people back to work, he adds, a test that has “less than perfect” sensitivity will be acceptable if it is also inexpensive.
Yang counters that antigen tests could find a place as a diagnostic tool, yet the results they provide may be unable to serve as a much needed early warning signal. “If your goal is to detect somebody that has a virus that may be more contagious [with a greater volume of the pathogen], then maybe that does make sense,” he says. But if the objective of a periodic antigen test is to detect people early in infection, “there will be less virus, and so sensitivity will be a big issue.”
The acute need for this type of testing, however, will continue to provide momentum to this line of research. “Rapid tests are going to miss people who are sick, but they are still very valuable, because they take just a few minutes to test somebody,” says Gigi Gronvall, an immunologist at the Johns Hopkins Center for Health Security. “If we’re able to scale up PCR, that will give you a more accurate, sensitive result. But there is some value at the point of care to having a screen like this.”
Ultimately, these debates may be put to rest in a few years. “Getting testing broadly is clearly something that we need to contain the epidemic. But all of this is a stopgap,” says Karla Satchell, a microbiologist at the Northwestern University Feinberg School of Medicine. “What we really need is a vaccine.”
Read more about the coronavirus outbreak from Scientific American here, and read coverage from our international network of magazines here.


scientificamerican--2020-09-29--Ninety Percent of U.S. Cars Must Be Electric by 2050 to Meet Climate Goals

The United States is not expected to electrify passenger cars fast enough to stay on track with the Paris climate accord ’ s goal of limiting global warming to 2 degrees Celsius , according to a new study .
Published in the journal Nature Climate Change yesterday , the study by engineers at the University of Toronto concludes that 90 % of light-duty cars on American roads would need to be electric by 2050 to keep the transportation sector in line with climate mitigation targets .
That might mean requiring all of the nation ’ s new car sales to @ @ @ @ @ @ @ the state target established by California Gov .
Gavin Newsom ( D ) in an announcement last week .
The prospect of a national ban on gasoline-fueled cars emerged throughout the Democratic primaries , where several candidates proposed a 100 % EV sales policy for 2035 or earlier .
Democratic presidential candidate Joe Biden favors the idea of phasing out gasoline cars but hasn ’ t signed on to a timeline ( Energywire , Feb. 14 ) .
If California ’ s 2035 target were adopted and implemented nationally , 350 million electric @ @ @ @ @ @ @ , the study found .
Those would fuel up using the equivalent of 41 % of the nation ’ s total power demand in 2018 , creating challenges for the grid , in addition to requiring “ excessive amounts ” of critical minerals like lithium and cobalt , the authors wrote .
“ We need to deploy electric vehicles .
But we also need to be realistic that they ’ re probably not sufficient on their own , ” said lead author Alexandre Milovanoff , an energy and sustainability researcher at the University @ @ @ @ @ @ @ on switching from gas cars to battery-electrics or fuel-cell vehicles , he said , policymakers should simultaneously aim to reduce the public ’ s dependence on personal cars .
Over coming decades , the number of miles racked up by the average car is projected to continue increasing .
But if travel demand were frozen at current levels , just 51 % of all cars on the road in the United States would need to be electrics in 2050 to meet emissions targets set out in the global Paris accord .
That would @ @ @ @ @ @ @ car sales by 2030 , a goal laid out by the International Energy Agency three years ago .
Huge infusions of money for public transit would be necessary to significantly reduce the nation ’ s reliance on passenger cars .
“ It has to be about equity , ” Milovanoff said of carbon dioxide reductions .
“ It ’ s about making sure all communities can access these systems.
” Land use changes could make it easier for people to live closer to their destinations , as well as to get around on @ @ @ @ @ @ @ New road tolls or taxes on car sales could discourage drivers from buying or using their own cars .
The authors noted another option for driving down emissions : fuel efficiency rules based on a vehicle ’ s weight rather than the “ footprint ” approach .
That would encourage car companies to roll out smaller , less energy-intensive models .
That change would better align U.S. and European standards .
The grid ’ s carbon intensity would also prove crucial in determining the effect of EV adoption .
The authors assumed that @ @ @ @ @ @ @ 2050 , combining the use of carbon capture technology , renewable energy and nuclear power .
“ So many cities in the U.S. don ’ t even have pavement for pedestrians , or a well-developed subway or bus system , ” Milovanoff said .
“ It comes from the fact that these cities are vehicle-centered .
They ’ re built on the premise that we ’ ll always use vehicles.
” Reprinted from Climatewire with permission from E & E News .
E & E provides daily coverage of essential energy and environmental @ @ @ @

The United States is not expected to electrify passenger cars fast enough to stay on track with the Paris climate accord’s goal of limiting global warming to 2 degrees Celsius, according to a new study.
Published in the journal Nature Climate Change yesterday, the study by engineers at the University of Toronto concludes that 90% of light-duty cars on American roads would need to be electric by 2050 to keep the transportation sector in line with climate mitigation targets.
That might mean requiring all of the nation’s new car sales to be electric as early as 2035, the state target established by California Gov. Gavin Newsom (D) in an announcement last week.
The prospect of a national ban on gasoline-fueled cars emerged throughout the Democratic primaries, where several candidates proposed a 100% EV sales policy for 2035 or earlier. Democratic presidential candidate Joe Biden favors the idea of phasing out gasoline cars but hasn’t signed on to a timeline (Energywire, Feb. 14).
If California’s 2035 target were adopted and implemented nationally, 350 million electric cars would ply the roads in 2050, the study found.
Those would fuel up using the equivalent of 41% of the nation’s total power demand in 2018, creating challenges for the grid, in addition to requiring “excessive amounts” of critical minerals like lithium and cobalt, the authors wrote.
“We need to deploy electric vehicles. But we also need to be realistic that they’re probably not sufficient on their own,” said lead author Alexandre Milovanoff, an energy and sustainability researcher at the University of Toronto.
Instead of focusing exclusively on switching from gas cars to battery-electrics or fuel-cell vehicles, he said, policymakers should simultaneously aim to reduce the public’s dependence on personal cars.
Over coming decades, the number of miles racked up by the average car is projected to continue increasing. But if travel demand were frozen at current levels, just 51% of all cars on the road in the United States would need to be electrics in 2050 to meet emissions targets set out in the global Paris accord. That would mean achieving 30% penetration of new car sales by 2030, a goal laid out by the International Energy Agency three years ago.
Huge infusions of money for public transit would be necessary to significantly reduce the nation’s reliance on passenger cars.
“It has to be about equity,” Milovanoff said of carbon dioxide reductions. “It’s about making sure all communities can access these systems.”
Land use changes could make it easier for people to live closer to their destinations, as well as to get around on foot or bicycle, he added. New road tolls or taxes on car sales could discourage drivers from buying or using their own cars.
The authors noted another option for driving down emissions: fuel efficiency rules based on a vehicle’s weight rather than the “footprint” approach. That would encourage car companies to roll out smaller, less energy-intensive models. That change would better align U.S. and European standards.
The grid’s carbon intensity would also prove crucial in determining the effect of EV adoption. The authors assumed that the U.S. electric grid is decarbonized by 2050, combining the use of carbon capture technology, renewable energy and nuclear power.
“So many cities in the U.S. don’t even have pavement for pedestrians, or a well-developed subway or bus system,” Milovanoff said. “It comes from the fact that these cities are vehicle-centered. They’re built on the premise that we’ll always use vehicles.”
Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.


scientificamerican--2020-09-29--Online Reptile Trade Is a Free-for-All That Threatens Thousands of Species

Cave geckos exemplify evolution at its most fantastic .
Some have bloodred eyes and sport bright yellow bands down their dark body .
Others are Popsicle blue or bear camouflagelike patterns of fiery orange and brown .
Many species of these lizards are only found over a tiny range , such as a single limestone hill in China .
More than a dozen are listed as threatened with extinction , some of them critically so , by the International Union for Conservation of Nature ( IUCN ) .
Yet partly because they are rare and imperiled , cave geckos are @ @ @ @ @ @ @ They are among the nearly 4,000 reptile species—including highly endangered ones—that are routinely traded online , according to a paper published on Tuesday in Nature Communications .
Animals from 90 percent of those species , representing half of the individual reptiles traded on the Web , are captured from the wild , the authors found .
And the majority of these species are not included in any international regulations meant to ensure their trade is sustainable .
“ At the moment , the status quo is that anything can be traded until you @ @ @ @ @ @ @ says study co-author Alice Hughes , an ecologist at the Chinese Academy of Sciences .
“ This leaves thousands of species vulnerable to extinction.
” As the new paper shows , no organization keeps track of global trade data for species that are not included in the Convention on International Trade in Endangered Species of Wild Fauna and Flora ( CITES ) , a global treaty created in 1973 to ensure commerce involving wild species does not imperil them .
Hughes was interested in determining how representative CITES is in terms of the @ @ @ @ @ @ @ , lizards , turtles , tortoises and crocodilians , among others .
She and her colleagues compiled official data from 2000 to 2019 from CITES and U.S .
Fish and Wildlife Service records and then gathered their own information from Web sites that sell reptiles .
For the latter , they used an algorithm to identify and scrape the data from nearly 24,000 pages at 151 Web sites in English , German , Spanish , Japanese and French .
The researchers tallied 3,943 species , or 36 percent of all known reptile species @ @ @ @ @ @ @ those that are legal to trade as pets .
But the question of whether a given species can be legally sold internationally is not automatically linked to its conservation status .
More than a third of the reptiles on the list—including Borneo ’ s earless monitor lizard and Madagascar ’ s Uroplatus finaritra , a leaf-tailed gecko—have not been evaluated for their conservation status .
This situation means scientists have no way of knowing if trade impacts those species ’ survival .
Of the ones that have been evaluated , more than 500 @ @ @ @ @ @ @ danger of extinction .
That group includes more than 100 species that are critically endangered , such as Lauhachinda ’ s cave gecko in Thailand and Yamashina ’ s ground gecko in Japan .
The study ’ s findings still underestimate the true number of reptile species caught up in trade , Hughes says , because its analysis did not include social media sites—where previous research has shown that high levels of wildlife trade take place .
The paper also lacks results from Web sites in languages other than the five it considered @ @ @ @ @ @ @ attempt to quantify how many individuals of each species are sold online , says Vincent Nijman , a wildlife trade expert at Oxford Brookes University in England , who was not involved in the study .
“ The paper highlights that , indeed , trade affects a very large number of species , ” he says .
“ But if you really want to change policy , you must have a more definite idea of the real volumes involved .
That ’ s not a criticism of this study , but that ’ @ @ @ @ @ @ @ with future work.
” Hughes and her colleagues found that 79 percent of reptile species sold online are not regulated by CITES .
For those species and others that are not part of the treaty , quantities would likely be impossible to determine , Hughes says , because no agency tracks them .
To be included in CITES , species must go through a lengthy nomination process—one that , on average , takes more than 10 years to complete , according to a 2019 Science paper .
Just showing that trade threatens a @ @ @ @ @ @ @ warrant adding it to the treaty , because commercial interests often take precedence over science , conservationists have warned .
“ I attended the CITES conference last year in Geneva , and I was frankly stunned by how much of it seemed to be purely economically motivated , ” Hughes says .
The academic world perhaps “ underestimates the overall cost of regulating species under CITES , ” the CITES Secretariat wrote in a statement to Scientific American .
“ It is probably true that the strong compliance mechanisms that CITES developed over @ @ @ @ @ @ @ is feared and famous , have more impact if species are involved that are commercially important ” for the relevant countries where those species are found .
John Scanlon , former secretary-general of CITES , who was not involved in the study , says he does not share the observation that the treaty ’ s members often value economic considerations over scientific ones .
Lesser known species of birds , insects , frogs , lizards , rodents , snakes , turtles , and more “ do not make the headlines , like issues @ @ @ @ @ @ @ , elephants and rhinos , but they do make up a majority of the listing proposals , ” he says .
“ CITES is imperfect , but it has proven to be quite effective.
” That said , “ there are clearly gaps in our knowledge and data on trade in unlisted species , including reptiles , ” Scanlon adds .
“ This report shows that parties should be proposing more reptiles for listing under CITES , which , on the face of this report , looks warranted.
” Hughes questions whether the @ @ @ @ @ @ @ ensuring the pet trade does not imperil species , however .
A more effective strategy , she says , would be for individual countries to pass legislation banning the import of certain wild-caught animals , as the U.S. and European Union have already done for many bird species .
At the same time , the pet industry could transition to captive-breeding operations with necessary oversight .
“ We are not against keeping exotic animals as pets , but it has to be sustainable , ” Hughes says .
“ We need to develop @ @ @ @ @ @ @ does not lead to species extinctions .
”

Cave geckos exemplify evolution at its most fantastic. Some have bloodred eyes and sport bright yellow bands down their dark body. Others are Popsicle blue or bear camouflagelike patterns of fiery orange and brown. Many species of these lizards are only found over a tiny range, such as a single limestone hill in China. More than a dozen are listed as threatened with extinction, some of them critically so, by the International Union for Conservation of Nature (IUCN).
Yet partly because they are rare and imperiled, cave geckos are all the rage among reptile collectors. They are among the nearly 4,000 reptile species—including highly endangered ones—that are routinely traded online, according to a paper published on Tuesday in Nature Communications. Animals from 90 percent of those species, representing half of the individual reptiles traded on the Web, are captured from the wild, the authors found. And the majority of these species are not included in any international regulations meant to ensure their trade is sustainable. “At the moment, the status quo is that anything can be traded until you say it can’t,” says study co-author Alice Hughes, an ecologist at the Chinese Academy of Sciences. “This leaves thousands of species vulnerable to extinction.”
As the new paper shows, no organization keeps track of global trade data for species that are not included in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), a global treaty created in 1973 to ensure commerce involving wild species does not imperil them. Hughes was interested in determining how representative CITES is in terms of the international reptile trade, which affects snakes, lizards, turtles, tortoises and crocodilians, among others. She and her colleagues compiled official data from 2000 to 2019 from CITES and U.S. Fish and Wildlife Service records and then gathered their own information from Web sites that sell reptiles. For the latter, they used an algorithm to identify and scrape the data from nearly 24,000 pages at 151 Web sites in English, German, Spanish, Japanese and French.
The researchers tallied 3,943 species, or 36 percent of all known reptile species, for sale online. Most were those that are legal to trade as pets. But the question of whether a given species can be legally sold internationally is not automatically linked to its conservation status. More than a third of the reptiles on the list—including Borneo’s earless monitor lizard and Madagascar’s Uroplatus finaritra, a leaf-tailed gecko—have not been evaluated for their conservation status. This situation means scientists have no way of knowing if trade impacts those species’ survival. Of the ones that have been evaluated, more than 500 are listed by the IUCN as in danger of extinction. That group includes more than 100 species that are critically endangered, such as Lauhachinda’s cave gecko in Thailand and Yamashina’s ground gecko in Japan.
The study’s findings still underestimate the true number of reptile species caught up in trade, Hughes says, because its analysis did not include social media sites—where previous research has shown that high levels of wildlife trade take place. The paper also lacks results from Web sites in languages other than the five it considered.
Additionally, the research does not attempt to quantify how many individuals of each species are sold online, says Vincent Nijman, a wildlife trade expert at Oxford Brookes University in England, who was not involved in the study. “The paper highlights that, indeed, trade affects a very large number of species,” he says. “But if you really want to change policy, you must have a more definite idea of the real volumes involved. That’s not a criticism of this study, but that’s ultimately where we have to go with future work.”
Hughes and her colleagues found that 79 percent of reptile species sold online are not regulated by CITES. For those species and others that are not part of the treaty, quantities would likely be impossible to determine, Hughes says, because no agency tracks them.
To be included in CITES, species must go through a lengthy nomination process—one that, on average, takes more than 10 years to complete, according to a 2019 Science paper. Just showing that trade threatens a species is also not necessarily enough to warrant adding it to the treaty, because commercial interests often take precedence over science, conservationists have warned. “I attended the CITES conference last year in Geneva, and I was frankly stunned by how much of it seemed to be purely economically motivated,” Hughes says.
The academic world perhaps “underestimates the overall cost of regulating species under CITES,” the CITES Secretariat wrote in a statement to Scientific American. “It is probably true that the strong compliance mechanisms that CITES developed over the years, and for which it is feared and famous, have more impact if species are involved that are commercially important” for the relevant countries where those species are found.
John Scanlon, former secretary-general of CITES, who was not involved in the study, says he does not share the observation that the treaty’s members often value economic considerations over scientific ones. Lesser known species of birds, insects, frogs, lizards, rodents, snakes, turtles, and more “do not make the headlines, like issues do with cheetah, giraffes, lions, elephants and rhinos, but they do make up a majority of the listing proposals,” he says. “CITES is imperfect, but it has proven to be quite effective.”
That said, “there are clearly gaps in our knowledge and data on trade in unlisted species, including reptiles,” Scanlon adds. “This report shows that parties should be proposing more reptiles for listing under CITES, which, on the face of this report, looks warranted.”
Hughes questions whether the treaty is the best tool for quickly ensuring the pet trade does not imperil species, however. A more effective strategy, she says, would be for individual countries to pass legislation banning the import of certain wild-caught animals, as the U.S. and European Union have already done for many bird species. At the same time, the pet industry could transition to captive-breeding operations with necessary oversight. “We are not against keeping exotic animals as pets, but it has to be sustainable,” Hughes says. “We need to develop better systems for making sure pet trade does not lead to species extinctions.”


scientificamerican--2020-09-29--The American Public Still Trusts Scientists, Says a New Pew Survey

Public trust of the scientific community in the United States is as strong as ever , according to a new poll just released today by the Pew Research Center , confirming polling results dating back to the 1970s .
Thirty-eight percent of those polled in Pew ’ s survey in the U.S. say that they have a lot of trust in scientists to do what is right for the public .
Those polled also place a lot of trust in scientific institutions as compared to others in the U.S. Pew ’ s data show respondents only ranked the military as @ @ @ @ @ @ @ ranking lower trust in others like the national government , news media and business leaders .
That trust in science is of heightened importance right now , particularly in the U.S. , where the novel coronavirus continues to spread and has now killed over 200,000 people .
With a lackluster government response , the public has been left on their own with the responsibility to follow guidance and advice provided by public health experts to control the spread of the virus .
It ’ s encouraging to see that multiple polls show the @ @ @ @ @ @ @ scientific community and in medical and government institutions overseeing the virus response .
Yet , regardless of the public ’ s trust in science , the U.S. has the most coronavirus cases and deaths worldwide and one of the highest infection rates .
This raises an important question : is public trust in science enough to drive actions at a scale sufficient to effectively combat a nationwide emergency like that of a pandemic ?
The answer seems to be “ no.
” In some countries with far less trust in science ( including @ @ @ @ @ @ @ the new polling data from Pew ) , the novel coronavirus has been better contained .
It is difficult to know exactly why Taiwan ’ s and South Korea ’ s responses seem to be more effective , and it is important to note that comparing coronavirus data among countries is difficult for multiple reasons .
But something is different ; Taiwan , for instance , has 23 million people , but has seen only 500 cases and seven deaths .
Taiwan attributes its effective response to its memory of the significant effects @ @ @ @ @ @ @ country .
Early recognition of mysterious pneumonia cases in China and suspicions that Beijing was not being transparent about them spurred Taiwan ’ s government to act quickly .
They setup a command center , screened all passengers coming in from Wuhan , China , put in place early travel restrictions , required a 14 day quarantine for all foreign arrivals , and implemented contact tracing and testing weeks before many other countries reacted .
Taiwan also has had no problem convincing people to wear masks given the recent memory of the havoc @ @ @ @ @ @ @ Of those polled in the Pew survey from Taiwan , only 17 percent of respondents said they had a lot of trust in scientists to do what is right for their country .
Taiwan had the second lowest reported trust in scientists in the poll ( behind South Korea at 14 percent ) .
Among the countries polled in Pew ’ s data , 59 percent of those polled in India said that they trust scientists a lot to do what is right for their country—more than any other country polled in the @ @ @ @ @ @ @ million coronavirus cases and is predicted to overtake the U.S. as the nation worst-hit by the virus .
A lockdown was imposed in India during March , but a study released by the Indian Council of Medical Research suggests that it was leaky , with transmission occurring as people poured out of cities into rural areas .
Low testing rates , poor social protections , and a fragile health care system also have likely led to the spread of the virus in the country .
The U.S. , India , South Korea and @ @ @ @ @ @ @ public trust in science does not match the number of coronavirus cases , deaths or infection rates of a country .
Instead , each case seems more dependent on government response ( and likely , in the case of Taiwan , a recent memory of the devastation a viral epidemic can cause ) .
Just as with our response to climate change , individual actions do not seem to be solely enough to solve such a large science-based issue .
And if our government ’ s response affects the spread of the coronavirus @ @ @ @ @ @ @ U.S. may be in worse trouble than previously thought .
While the U.S. public overall trusts the scientific community , many of the country ’ s responses have been driven by politics rather than scientific evidence .
We at the Union of Concerned Scientists have now documented over 160 instances since 2017 where politics have trumped scientific evidence in decisions that affect public health and safety .
On the federal government ’ s response to the coronavirus specifically , we have seen federal scientists ignored , censored , bullied and accused of sedition @ @ @ @ @ @ @ that public trust in science or that wearing a mask when you leave your home are not important ; they are both very important so please keep trusting in science and donning those masks !
But if we are hoping that such trust in science will be enough to drive the huge collective actions needed to keep the novel coronavirus from spreading , I ’ m afraid such hope may be misplaced .
What we need more than ever is a coordinated and effective science-based response from government leaders .
The public trusts @ @ @ @ @ @ @ too .
We certainly do not have that at this moment .

Public trust of the scientific community in the United States is as strong as ever, according to a new poll just released today by the Pew Research Center, confirming polling results dating back to the 1970s. Thirty-eight percent of those polled in Pew’s survey in the U.S. say that they have a lot of trust in scientists to do what is right for the public. Those polled also place a lot of trust in scientific institutions as compared to others in the U.S. Pew’s data show respondents only ranked the military as more trustworthy than scientific institutions, while ranking lower trust in others like the national government, news media and business leaders.
That trust in science is of heightened importance right now, particularly in the U.S., where the novel coronavirus continues to spread and has now killed over 200,000 people. With a lackluster government response, the public has been left on their own with the responsibility to follow guidance and advice provided by public health experts to control the spread of the virus. It’s encouraging to see that multiple polls show the U.S. public still has trust in the scientific community and in medical and government institutions overseeing the virus response.
Credit: Amanda Montañez; Source: General Social Survey, NORC at the University of Chicago
Yet, regardless of the public’s trust in science, the U.S. has the most coronavirus cases and deaths worldwide and one of the highest infection rates. This raises an important question: is public trust in science enough to drive actions at a scale sufficient to effectively combat a nationwide emergency like that of a pandemic? The answer seems to be “no.”
In some countries with far less trust in science (including Taiwan and South Korea, according to the new polling data from Pew), the novel coronavirus has been better contained. It is difficult to know exactly why Taiwan’s and South Korea’s responses seem to be more effective, and it is important to note that comparing coronavirus data among countries is difficult for multiple reasons. But something is different; Taiwan, for instance, has 23 million people, but has seen only 500 cases and seven deaths.
Credit: Amanda Montañez; Sources: Science and Scientists Held in High Esteem across Global Publics. Cary Funk, Alec Tyson, Brian Kennedy and Courtney Johnson. Pew Research Center, September 2020 (survey data); COVID-19 Dashboard, Center for Systems Science and Engineering, Johns Hopkins University (COVID-19 data)
Taiwan attributes its effective response to its memory of the significant effects of the 2003 SARS outbreak in the country. Early recognition of mysterious pneumonia cases in China and suspicions that Beijing was not being transparent about them spurred Taiwan’s government to act quickly. They setup a command center, screened all passengers coming in from Wuhan, China, put in place early travel restrictions, required a 14 day quarantine for all foreign arrivals, and implemented contact tracing and testing weeks before many other countries reacted. Taiwan also has had no problem convincing people to wear masks given the recent memory of the havoc caused by the 2003 SARS outbreak. Of those polled in the Pew survey from Taiwan, only 17 percent of respondents said they had a lot of trust in scientists to do what is right for their country. Taiwan had the second lowest reported trust in scientists in the poll (behind South Korea at 14 percent).
Among the countries polled in Pew’s data, 59 percent of those polled in India said that they trust scientists a lot to do what is right for their country—more than any other country polled in the survey. India currently has over 5.6 million coronavirus cases and is predicted to overtake the U.S. as the nation worst-hit by the virus. A lockdown was imposed in India during March, but a study released by the Indian Council of Medical Research suggests that it was leaky, with transmission occurring as people poured out of cities into rural areas. Low testing rates, poor social protections, and a fragile health care system also have likely led to the spread of the virus in the country.
The U.S., India, South Korea and Taiwan are not the only cases where public trust in science does not match the number of coronavirus cases, deaths or infection rates of a country. Instead, each case seems more dependent on government response (and likely, in the case of Taiwan, a recent memory of the devastation a viral epidemic can cause). Just as with our response to climate change, individual actions do not seem to be solely enough to solve such a large science-based issue.
And if our government’s response affects the spread of the coronavirus more than our individual actions, the U.S. may be in worse trouble than previously thought. While the U.S. public overall trusts the scientific community, many of the country’s responses have been driven by politics rather than scientific evidence. We at the Union of Concerned Scientists have now documented over 160 instances since 2017 where politics have trumped scientific evidence in decisions that affect public health and safety. On the federal government’s response to the coronavirus specifically, we have seen federal scientists ignored, censored, bullied and accused of sedition.
This is all not to say that public trust in science or that wearing a mask when you leave your home are not important; they are both very important so please keep trusting in science and donning those masks! But if we are hoping that such trust in science will be enough to drive the huge collective actions needed to keep the novel coronavirus from spreading, I’m afraid such hope may be misplaced. What we need more than ever is a coordinated and effective science-based response from government leaders. The public trusts the science, but our leaders must too.
We certainly do not have that at this moment.


scientificamerican--2020-09-30--We Need Federal Action to Prevent the Next Pandemic

It is no small task to predict which of the hundreds of thousands of unknown pathogens existing naturally in animals will spill over to people and cause the next pandemic .
But one thing is clear : A major factor driving spillover events such as the current COVID-19 pandemic is the trade in live and fresh wildlife for human consumption ( whether legal or illegal ) .
Removing wild animals from nature and transporting them to commercial markets where the close proximity of animals and people poses a significant public health risk is a practice that can no longer be @ @ @ @ @ @ @ that pass between people and animals—affect millions of people each year , with three quarters of new human pathogens identified in the past three decades originating in animals .
The U.S. government must reengage in its commitment to address zoonotic diseases .
While the first Coronavirus Supplemental Funding Package included $ 435 million for global health programs , zoonotic surveillance was not one of the priority activities .
After leading for more than two decades in the establishment of global early warning systems for epidemics , the USG must reestablish its preeminent role @ @ @ @ @ @ @ ever .
Habitat destruction , deforestation and the conversion of land for industrial-scale farming and other uses accelerate our ability to take animals from wild places and put wildlife—and the pathogens they contain—in ever more frequent contact with each other and people .
Once an animal enters a commercial supply chain , the risks of viral recombination , emergence and transmission increases .
Rigorous enforcement of existing laws , regulations and international treaties that deal with wildlife trade and markets is critical , but will not be enough .
Legal and sustainable trade @ @ @ @ @ @ @ Indeed , the preponderance of scientific evidence suggests that the coronavirus responsible for the global COVID-19 pandemic originated in a wildlife species—most likely a bat .
In more rural and poorer parts of the world , local people frequently rely on wild birds and mammals for food because they have no alternatives .
As a global community , we must work to ensure that they gain access to sustainably produced poultry , fish , invertebrates and plants to both meet dietary needs and reduce the risk of exposure to new zoonotic pathogens .
@ @ @ @ @ @ @ their families , generate income and to retain their cultural identity .
Outreach to raise traditional hunters ’ awareness of ways to minimize zoonotic disease transfer will reduce risks to their health and to the general public .
The legal and illegal transport to markets of live wildlife leads both to their injury and stress , resulting in the “ shedding ” of more pathogens in animals ’ urine , feces and blood , facilitating mutations and recombinations that render viruses a direct disease threat to people .
If we are to reduce @ @ @ @ @ @ @ , we must adopt a comprehensive approach for which the U.S. government has a critical role to play .
Ending the global commercial trade in live and fresh wildlife for human consumption constitutes a major pillar and will require international cooperation with governments , intergovernmental organizations , and communities .
Senators John Cornyn and Cory Booker and Representatives Mike Quigley and Fred Upton introduced bipartisan legislation yesterday that would take several important steps towards closing markets that trade in live terrestrial wildlife , starting with a U.S. ban on the import , export @ @ @ @ @ @ @ human consumption .
This bill directs the Department of State to work with other nations and international organizations to push for similar bans of markets that trade in live wildlife for human consumption around the world , and would boost efforts to monitor the emergence and spread of zoonotic diseases .
The legislation also provides resources to develop appropriate alternative sources of food to help remote communities that rely on hunting wildlife for food security .
Prompt passage of this legislation would show U.S. leadership on an issue with which the world continues @ @ @ @ @ @ @ both a nonpartisan zoonotic disease interagency task force headed by the president ’ s national security advisor and a new “ One Health ” strategy to leverage the public health , wildlife health and livestock veterinary expertise necessary to combat the current and future pandemics .
We need a new paradigm to avoid future pandemics .
When we view the hundreds of thousands of unknown pathogens against the human health , global and national security , economic , social and ecological costs of the current pandemic , it is clear that a failure @ @ @ @ @ @ @ grossly negligent .
The U.S. government has an opportunity to lead in avoiding future pandemics .
By its very nature , a pandemic is not a one-country problem .
Nor is it a one-party problem .
The COVID-19 crisis can be a wake-up call for us all to bring balance back to our fractured relationship with nature , or it can be just the latest in a continuing series of global health crises .
The choice is ours .

It is no small task to predict which of the hundreds of thousands of unknown pathogens existing naturally in animals will spill over to people and cause the next pandemic. But one thing is clear: A major factor driving spillover events such as the current COVID-19 pandemic is the trade in live and fresh wildlife for human consumption (whether legal or illegal).
Removing wild animals from nature and transporting them to commercial markets where the close proximity of animals and people poses a significant public health risk is a practice that can no longer be tolerated. Zoonoses—the term for infectious diseases that pass between people and animals—affect millions of people each year, with three quarters of new human pathogens identified in the past three decades originating in animals.
The U.S. government must reengage in its commitment to address zoonotic diseases. While the first Coronavirus Supplemental Funding Package included $435 million for global health programs, zoonotic surveillance was not one of the priority activities. After leading for more than two decades in the establishment of global early warning systems for epidemics, the USG must reestablish its preeminent role.
Our voice is needed more than ever. Habitat destruction, deforestation and the conversion of land for industrial-scale farming and other uses accelerate our ability to take animals from wild places and put wildlife—and the pathogens they contain—in ever more frequent contact with each other and people. Once an animal enters a commercial supply chain, the risks of viral recombination, emergence and transmission increases.
Rigorous enforcement of existing laws, regulations and international treaties that deal with wildlife trade and markets is critical, but will not be enough. Legal and sustainable trade is no protection against virus spillover. Indeed, the preponderance of scientific evidence suggests that the coronavirus responsible for the global COVID-19 pandemic originated in a wildlife species—most likely a bat.
In more rural and poorer parts of the world, local people frequently rely on wild birds and mammals for food because they have no alternatives. As a global community, we must work to ensure that they gain access to sustainably produced poultry, fish, invertebrates and plants to both meet dietary needs and reduce the risk of exposure to new zoonotic pathogens.
Indigenous peoples use wild animals to feed their families, generate income and to retain their cultural identity. Outreach to raise traditional hunters’ awareness of ways to minimize zoonotic disease transfer will reduce risks to their health and to the general public. The legal and illegal transport to markets of live wildlife leads both to their injury and stress, resulting in the “shedding” of more pathogens in animals’ urine, feces and blood, facilitating mutations and recombinations that render viruses a direct disease threat to people.
If we are to reduce the likelihood of future pandemics like COVID-19, we must adopt a comprehensive approach for which the U.S. government has a critical role to play. Ending the global commercial trade in live and fresh wildlife for human consumption constitutes a major pillar and will require international cooperation with governments, intergovernmental organizations, and communities.
Senators John Cornyn and Cory Booker and Representatives Mike Quigley and Fred Upton introduced bipartisan legislation yesterday that would take several important steps towards closing markets that trade in live terrestrial wildlife, starting with a U.S. ban on the import, export and domestic sale of live wildlife for human consumption. This bill directs the Department of State to work with other nations and international organizations to push for similar bans of markets that trade in live wildlife for human consumption around the world, and would boost efforts to monitor the emergence and spread of zoonotic diseases.
The legislation also provides resources to develop appropriate alternative sources of food to help remote communities that rely on hunting wildlife for food security. Prompt passage of this legislation would show U.S. leadership on an issue with which the world continues to struggle
Separately, we must establish both a nonpartisan zoonotic disease interagency task force headed by the president’s national security advisor and a new “One Health” strategy to leverage the public health, wildlife health and livestock veterinary expertise necessary to combat the current and future pandemics.
We need a new paradigm to avoid future pandemics. When we view the hundreds of thousands of unknown pathogens against the human health, global and national security, economic, social and ecological costs of the current pandemic, it is clear that a failure to address the root cause would be grossly negligent.
The U.S. government has an opportunity to lead in avoiding future pandemics. By its very nature, a pandemic is not a one-country problem. Nor is it a one-party problem. The COVID-19 crisis can be a wake-up call for us all to bring balance back to our fractured relationship with nature, or it can be just the latest in a continuing series of global health crises. The choice is ours.


scientificamerican--2020-09-30--Everything Scientists Know So Far about the First Interstellar Objects Ever Detected

Late in the evening of October 24 , 2017 , an e-mail arrived containing tantalizing news of the heavens .
Astronomer Davide Farnocchia of NASA 's Jet Propulsion Laboratory was writing to one of us ( Jewitt ) about a new object in the sky with a very strange trajectory .
Discovered six days earlier by University of Hawaii astronomer Robert Weryk , the object , initially dubbed P10Ee5V , was traveling so fast that the sun could not keep it in orbit .
Instead of its predicted path being a closed ellipse , its orbit was open , indicating @ @ @ @ @ @ @ We still need more data , ” Farnocchia wrote , “ but the orbit appears to be hyperbolic.
” Within a few hours , Jewitt wrote to Jane Luu , a long-time collaborator with Norwegian connections , about observing the new object with the Nordic Optical Telescope in Spain .
Many other observatories around the world were simultaneously scrambling to spot it .
So began a new era in astronomy .
Renamed C/2017 U1 ( the “ C ” standing for “ comet ” ) , then A/2017 U1 ( for “ asteroid @ @ @ @ @ @ @ ‘ Oumuamua , the object turned out to be the first body astronomers have ever seen in the solar system that originated outside it .
The “ 1I ” in its designation indicates its official status as the first known interstellar object , and the name ‘ Oumuamua— “ a messenger from afar arriving first ” in Hawaiian—was proposed by Weryk and his colleagues , who had used the Pan-STARRS telescope on the Hawaiian island of Maui to make the discovery .
What first caught the observers ' attention was the object 's @ @ @ @ @ @ @ After accounting for the pull of the sun 's gravity , ‘ Oumuamua had an excess speed of 26 kilometers a second ( 58,000 miles an hour ) .
No interaction with a solar system body could generate such a kick , and the sun 's gravity can not capture something moving so quickly ; ‘ Oumuamua had to have come from outside .
What kind of journey must this object have taken ?
From what we can tell , it could have been wandering the galaxy for hundreds of millions of years @ @ @ @ @ @ @ the direction of the bright star Vega , in the constellation Lyra , although Vega would not have been in the same spot when ‘ Oumuamua was there roughly 300,000 years ago .
Although astronomers have long believed that interstellar bodies pass through the solar system , actually finding one was a big surprise .
Only the year before , an exhaustive analysis by Toni Engelhardt , then at the University of Hawaii , and his colleagues concluded that prospects for identifying such an interstellar interloper “ appear to be bleak ” —they @ @ @ @ @ @ @ and faint for us to have much hope of finding them .
But as we discovered more about ‘ Oumuamua , our surprise turned into utter bewilderment .
Everything from its shape and size to its lack of cometlike properties ran counter to our expectations .
If this was a typical visitor from the greater universe , we had a lot to learn .
Observations from the Nordic Optical and other telescopes soon showed that ‘ Oumuamua lacked a tail and a surrounding coma of sublimated dust and ice transitioning directly from solid @ @ @ @ @ @ @ Rather , except for its unique orbit , ‘ Oumuamua looked like a rocky asteroid .
Still , given that it had come from interstellar space , where the average temperature is only a few degrees above absolute zero , the absence of evidence for sublimating ice was startling .
Water , the most abundant molecule in the universe after molecular hydrogen , should have been present .
And then there was the object 's shape .
Astronomers use the brightness of an asteroid as a measure of its size because bigger objects @ @ @ @ @ @ @ Oumuamua 's average brightness suggested a diameter of about 100 meters—quite small compared with most known asteroids .
Indeed , if ‘ Oumuamua had been as far away as the asteroid belt , where most of the asteroids in our solar system reside , we never would have seen it .
Instead we got lucky : it passed very close to us—about 60 million kilometers , which is only 40 percent of the average distance between the sun and Earth .
The brightness of most asteroids , shaped like lumpy potatoes rotating in @ @ @ @ @ @ @ alternately smaller and larger sides of themselves to Earth .
Observing this rotation produces a “ light curve , ” a plot of how the light changes that tells us the rotation period and gives us an estimate of the asteroid 's proportions .
In December 2017 scientists reported ‘ Oumuamua 's light curve .
At about eight hours its period was unremarkable compared with those of solar system asteroids .
But whereas most asteroids vary in brightness by 10 to 20 percent as they spin , ‘ Oumuamua changed by an unprecedented @ @ @ @ @ @ @ needlelike shape that sometimes presented a large and bright surface and sometimes showed only a very narrow edge .
The object 's resemblance in size and proportions to a large rocket—for example , the Saturn V , which measures about 110 meters by 10 meters—was hard to ignore .
Indeed , discarded rockets orbiting the sun are occasionally rediscovered by astronomers surveying the sky for asteroids and comets , as was the case for 2000 SG344 , a likely Apollo-program relic discovered in 2000 .
But the orbit of ‘ Oumuamua was too @ @ @ @ @ @ @ from the 1960s .
Could it be a rocket from another civilization ?
Incredible as it sounds , scientists could not immediately reject the possibility based on the available data .
While astronomers were pondering this conundrum , they got another surprise .
In June 2018 Italian astronomer Marco Micheli of the European Space Agency and his colleagues reported measurements of the shape of ‘ Oumuamua 's orbit , which revealed the action of a weak , rocketlike force pushing on the body in addition to the gravitational forces of the sun and @ @ @ @ @ @ @ known to exist in comets , arising from the asymmetric push of ices sublimating from the dayside of the comet 's core .
But ‘ Oumuamua is not a comet .
And it showed no evidence that it was losing mass at all , which could have explained the force .
Could it be that ‘ Oumuamua emitted only gas , which is harder to detect than comet dust ?
Possibly , but it would make ‘ Oumuamua unique : astronomers know of no other cosmic object that lets off gas but no @ @ @ @ @ @ @ ‘ Oumuamua might eject very large dust particles that were invisible to our telescopes .
In November 2018 Shmuel Bialy and Avi Loeb of the Center for Astrophysics | Harvard & Smithsonian proposed that the nongravitational force could be caused by sunlight , which exerts a weak pressure on any object placed in its path .
To experience enough radiation pressure that we could measure it , however , ‘ Oumuamua would have to be either extraordinarily thin like a sheet of Mylar ( the aluminized plastic used to make birthday balloons ) @ @ @ @ @ @ @ and Loeb suggested that the object could be a “ light sail , ” a flat , sail-shaped vehicle sent from another civilization and designed to be pushed through space by starlight .
As intriguing as that idea may be , most astronomers favor a natural origin for ‘ Oumuamua .
In February 2019 one of us ( Moro-Martín ) calculated that for ‘ Oumuamua to be propelled by sunlight , it would have to be 100 times less dense than air .
Such a cosmic dust bunny—an “ icy fractal aggregate ” @ @ @ @ @ @ @ of the protoplanetary disk of another star , where baby planets congeal out of ice and dust rubble .
This past summer Luu , Eirik Flekkøy and Renaud Toussaint , all at the University of Oslo , proposed that ‘ Oumuamua grew from a collection of dust particles in the coma of an active comet , then escaped .
This type of material is unknown on Earth but could conceivably survive in the ultimate vacuum of interstellar space .
Given how odd ‘ Oumuamua is , what might be most incredible of all @ @ @ @ @ @ @ common .
We know that this relatively tiny body was detected only because it passed close to Earth and that humans have had the capability to see such an object for only a few years ( the Pan-STARRS facility began operating in 2010 but reached full efficiency only recently ) .
Based on statistics alone , these two facts allowed scientists to estimate that the number of similar interstellar interlopers per unit volume of space is about one per 10 cubic AU ( one AU , or astronomical unit , is the distance @ @ @ @ @ @ @ Thus , in the planetary region of our solar system , defined as a sphere with the radius of Neptune 's orbit , there must be about 10,000 similar objects , of which ‘ Oumuamua is only the first one close enough to be detected in the operational lifetime of Pan-STARRS .
If these objects take about a decade to cross the planetary region , the average rate of interloper arrivals must be about three a day !
What , then , does this frequency suggest about the origin of ‘ Oumuamua ?
@ @ @ @ @ @ @ Saturn V–size rocket or a large piece of Mylar-like material across the galaxy and through our solar system , but why would they send so many ?
Even more astonishing , if we extrapolate our analysis from the solar system to the whole of the Milky Way , we find that there must be 1 × 1024 to 1 × 1025 ( a trillion trillion to 10 trillion trillion ) similar objects in our galaxy .
It is hard to believe that an extraterrestrial civilization would have the capacity to flood the galaxy @ @ @ @ @ @ @ it is even more difficult to see why it would do so .
Thus , given the maxim that extraordinary claims require extraordinary evidence , most astronomers think ‘ Oumuamua is just a weirdly shaped , but natural , piece of debris from elsewhere in the galaxy .
The sheer strangeness of ‘ Oumuamua left astronomers eagerly awaiting the discovery of the second interstellar interloper .
Would the next one be as peculiar , or would it look like a regular solar system comet or an asteroid without nongravitational motion ?
Without knowing @ @ @ @ @ @ @ predicted that the second object would arrive within a year or two , based on the estimate that there must be about one body like ‘ Oumuamua per 10 cubic AU .
To our delight , two years after ‘ Oumuamua , Ukrainian amateur astronomer Gennadiy Borisov discovered C/2019 Q4 using a homemade telescope ; it was soon renamed 2I/Borisov—the second interstellar object .
It has an orbit even more extreme than that of ‘ Oumuamua , but it appears to be a rather ordinary comet .
Measurements from the Hubble Space Telescope @ @ @ @ @ @ @ ‘ Oumuamua , with a radius between 0.2 and 0.5 kilometer .
In contrast to ‘ Oumuamua , 2I/Borisov displays no extreme light curve , and its nongravitational motion is simply a consequence of asymmetric outgassing as ice comes off its surface , just as in solar system comets .
This past March it briefly flared in brightness and then took on a doubled appearance as a small piece of the nucleus detached , something commonly observed with solar system comets .
In other words , this body is pretty much exactly what @ @ @ @ @ @ @ to be like .
Our expectations are based on theories of planet formation , which suggest a ready mechanism for kicking some objects out of their home planetary systems and into the galaxy , where they may eventually make their way to our little corner of the cosmos .
Studies suggest that planet formation begins in an orderly way but ends in a chaotic mess .
The sun , for instance , was born 4.6 billion years ago in a flattened , rotating disk that grew as a giant molecular cloud contracted under @ @ @ @ @ @ @ gas , ice and dust feeding the nascent star in its center was very dense , which allowed tiny grains to collide and stick to one another .
At first pebbles formed , then larger bodies known as planetesimals and , eventually , the planets .
Some of the planetesimals escaped further growth and heating when they were scattered to the outer solar system shortly after they formed .
There , in deep freeze , they have remained mostly unaltered ever since .
Sometimes , though , these bodies get scattered back into @ @ @ @ @ @ @ 's heat causes their ice to sublimate ; they develop tails of ejected material , and we call them comets .
Other planetesimals are expelled from the system entirely , destined to spend eternity drifting among the stars .
Once lost in the vastness of the Milky Way , such an object has a negligible chance of reentering the planetary system it came from , but it could certainly be deflected by the gravity of an alien star .
Given the chaos of this process and the numerous encounters ‘ Oumuamua and Borisov @ @ @ @ @ @ @ , we will likely never know precisely how long these objects have been adrift or determine with confidence where they came from .
Nevertheless , we can feel confident that Borisov is an ice-rich planetesimal from the outer regions of the planet-forming disk of an unknown star .
In fact , everything we have learned about Borisov—and the proof it offers that some interstellar objects look much like we expected—puts the strangeness of ‘ Oumuamua in stark relief .
Given the extraordinary differences between the two , there is no reason to assume @ @ @ @ @ @ @ Astronomers are still trying to puzzle out what ‘ Oumuamua is , and new ideas come up often .
One recent suggestion , proposed this past May by Darryl Seligman of the University of Chicago and Gregory Laughlin of Yale University , is that ‘ Oumuamua is a novel type of body made of molecular hydrogen ice—a cosmic iceberg that originated in the coldest regions of a molecular cloud .
In June , however , Loeb and Thiem Hoang of the Korea Astronomy and Space Science Institute argued that molecular hydrogen is so @ @ @ @ @ @ @ have formed in a molecular cloud nor have survived interstellar travel .
Another option , put forward in April by Yun Zhang of the National Astronomical Observatories of the Chinese Academy of Sciences and Douglas N. C. Lin of the University of California , Santa Cruz , is that ‘ Oumuamua might instead be shrapnel produced by gravitational shredding of a planet or other body passing too near its parent star .
‘ Oumuamua 's strange properties aside , the fact that the object was detected at all runs counter to the conventional @ @ @ @ @ @ @ suggests that interstellar visitors should be very rare .
We can estimate the number of interstellar planetesimals we expect to exist per unit volume of space based on the observed number of stars and on our knowledge of star and planet formation , stellar evolution and dynamics .
The calculation involves many uncertainties , but a generous upper limit is at least a tenth to a hundredth the size of the previously mentioned statistical frequency estimate of 10,000 such objects in the planetary region .
Put simply , we can not account for @ @ @ @ @ @ @ Perhaps as we detect more interlopers and understand them better , the inferred and estimated values of their space density will start to converge .
But it is also possible that we are missing an important source of interstellar objects—maybe some process in space other than the planetesimal scattering we have described creates bodies that find their way to us .
Besides teaching us about how planetary systems form , the discovery of interstellar visitors may have a bearing on one of the most fundamental mysteries in science : How did life on @ @ @ @ @ @ @ panspermia , is that the seeds of ancient organisms hitched a ride on asteroids hailing from other systems .
Just as we expect interstellar bodies to enter our solar system occasionally , we must also assume that they sometimes hit our planet .
Based on the value of one object per 10 cubic AU that we inferred from the detection of ‘ Oumuamua and 2I/Borisov , we can estimate that similar objects strike about once every 100 million to 200 million years , thousands of times less frequently than asteroids of comparable size @ @ @ @ @ @ @ in the atmosphere , but a few would actually reach the ground .
Scientists estimate that over the eons several billion tons of interstellar material must have crashed into Earth .
Could these impacts have delivered life to our planet ?
The modern scientific notion of panspermia dates back to the 19th century .
Surprisingly , asteroids and comets might be good protectors of fragile cellular life .
Damaging cosmic rays , capable of breaking DNA , penetrate only a few meters into solid material , so living cells buried inside rocks might @ @ @ @ @ @ @ hundreds of millions of years .
At near-zero interstellar temperatures , any cells would be in suspended animation .
They would need to withstand the shock of planetary impact , but this might not be as problematic as it sounds .
Experiments have already shown that earthly bacteria can survive impacts at cosmic speed .
Although there is no evidence that life spreads through the galaxy while riding in the bellies of asteroids and comets , given our present state of ignorance , we must acknowledge that this possibility remains .
To improve @ @ @ @ @ @ @ need to find more examples .
Currently , with only two to go on , our grasp is limited .
Fortunately , new developments in astronomy make it very likely that we will soon observe dozens of similar objects , and those discoveries will allow us to better pin down the statistics and to understand their physical properties .
Most professional telescopes have very small fields of view , often only a few thousandths of the area of the full moon .
But optics and large detectors are now capable of capturing the @ @ @ @ @ @ @ shot and the entire sky in a night or two of continuous scanning .
Powerful computers make it possible to compare successive all-sky scans to find moving objects , including interstellar interlopers .
Having a larger sample of interstellar objects will help us answer many questions about the objects themselves .
How many interlopers are strangely iceless and oblong like ‘ Oumuamua versus akin to a comet like 2I/Borisov ?
Are there bigger examples ?
Are there smaller ones ?
What are they made of ?
Are some really porous enough to be @ @ @ @ @ @ @ ?
New data from the Rubin Observatory , now under construction on a Chilean mountaintop , should provide fresh insights .
The Rubin telescope has a collecting mirror 8.4 meters in diameter and a three-billion-pixel detector that would have been unthinkable just a decade ago .
Each image from this gigantic camera will cover an area 40 times that of the moon , an enormous advance .
It will also systematically survey the sky more deeply than has ever been attempted and on a repeated basis .
This new facility is expected to @ @ @ @ @ @ @ with vast numbers of asteroids , comets and Kuiper belt objects from our own solar system .
To truly understand the nature of any given interloper , we would like to send a spacecraft to visit it or even land on it .
One practical problem is that there is not much time to make plans because these objects move so fast .
‘ Oumuamua faded to invisibility for even the largest telescopes within a few months of its discovery .
2I/Borisov will be too faint to detect within a year or two @ @ @ @ @ @ @ take a decade or more , including their design , approval , construction and launch , making it impossible to plan for any particular interstellar target .
A solution might be to send the spacecraft into a storage orbit before even knowing where the mission will go .
This is the idea behind the European Space Agency 's Comet Interceptor , due to be launched in 2028 .
The Interceptor will park at Earth 's L2 Lagrangian point 1.5 million kilometers away , where it can easily maintain a stable orbit as it @ @ @ @ @ @ @ .
The Interceptor lacks the power to rendezvous with an interloper unless one happens by chance to pass very close to L2 , however .
More capable rockets are intrinsically heavy and expensive to launch ; even if a flyby is possible , accelerating to hyperbolic orbit speed to grab a sample will not be easy .
Spacecraft powered by novel propulsion methods , such as light sails accelerated by a laser beam from Earth or by solar radiation pressure , are another option , but they involve difficulties of their own .
@ @ @ @ @ @ @ to closely examine an object that unequivocally originated beyond our solar system is extraordinary , and scientists have not been shy in proposing ways to do so .
One way or another , we will pry the secrets from our interstellar visitors .

Late in the evening of October 24, 2017, an e-mail arrived containing tantalizing news of the heavens. Astronomer Davide Farnocchia of the nasa Jet Propulsion Laboratory was writing to one of us (Jewitt) about a new object in the sky with a very strange trajectory. Discovered six days earlier by Robert Weryk, then a postdoctoral researcher at the University of Hawaii, the object, initially dubbed P10Ee5V, was traveling so fast that the sun could not keep it in orbit. Instead of its predicted path being a closed ellipse, its orbit was open, indicating that it would never return. “We still need more data,” Farnocchia wrote, “but the orbit appears to be hyperbolic.” Within a few hours Jewitt wrote to Jane Luu, a long-time collaborator with Norwegian connections, about observing the new object with the Nordic Optical Telescope in Spain. Many other observatories around the world were simultaneously scrambling to spot it.
So began a new era in astronomy. Renamed C/2017 U1 (the “C” standing for “comet”), then A/2017 U1 (for “asteroid”) and, finally, 1I/’Oumuamua, the object turned out to be the first body astronomers had ever seen in the solar system that originated outside it. The “1I” in its designation indicates its official status as the first-known interstellar object, and the name ‘Oumuamua—“a messenger from afar arriving first” in Hawaiian—was proposed by Weryk and his colleagues, who had used the Pan-STARRS telescope on the Hawaiian island of Maui to make the discovery.
What first caught the observers’ attention was the object’s extreme speed relative to the sun. After accounting for the pull of the sun’s gravity, ‘Oumuamua had an excess speed of 26 kilometers a second (58,000 miles an hour). No interaction with a solar system body could generate such a kick, and the sun’s gravity cannot capture something moving so quickly; ‘Oumuamua had to have come from outside.
What kind of journey must this object have taken? From what we can tell, it could have been wandering the galaxy for hundreds of millions of years. Observations suggest that it came from the direction of the bright star Vega, in the constellation Lyra, although Vega would not have been in the same spot when ‘Oumuamua was there roughly 300,000 years ago.
Although astronomers have long believed that interstellar bodies pass through the solar system, actually finding one was a big surprise. Only the year before, an exhaustive analysis by Toni Engelhardt, then at the University of Hawaii, and his colleagues concluded that prospects for identifying such an interstellar interloper “appear to be bleak”—they were thought to be just too small and faint for us to have much hope of finding them. But as we discovered more about ‘Oumuamua, our surprise turned into utter bewilderment. Everything from its shape and size to its lack of cometlike properties ran counter to our expectations. If this was a typical visitor from the greater universe, we had a lot to learn.
2I/BORISOV, the second known interstellar visitor, was first spotted in 2019. Credit: Ron Miller
Alien Artifact or Cosmic Dust Bunny?
Observations from the Nordic Optical and other telescopes soon showed that ‘Oumuamua lacked a tail and a surrounding coma of sublimated dust and ice transitioning directly from solid to gas—the hallmarks of a comet. Rather, except for its unique orbit, ‘Oumuamua looked like a rocky asteroid. Still, given that it had come from interstellar space, where the average temperature is only a few degrees above absolute zero, the absence of evidence for sublimating ice was startling. Water, the most abundant molecule in the universe after molecular hydrogen, should have been present.
And then there was the object’s shape. Astronomers use the brightness of an asteroid as a measure of its size because bigger objects reflect more sunlight to Earth. ‘Oumuamua’s average brightness suggested a diameter of about 100 meters—quite small compared with most known asteroids. Indeed, if ‘Oumuamua had been as far away as the asteroid belt, where most of the asteroids in our solar system reside, we never would have seen it. Instead we got lucky: it passed very close to us—about 60 million kilometers, which is only 40 percent of the average distance between the sun and Earth. The brightness of most asteroids, shaped like lumpy potatoes rotating in space, varies cyclically as they present alternately smaller and larger sides of themselves to Earth. Observing this rotation produces a “light curve,” a plot of how the light changes that tells us the rotation period and gives us an estimate of the asteroid’s proportions. In December 2017 scientists reported ‘Oumuamua’s light curve. At about eight hours its period was unremarkable compared with those of solar system asteroids. But whereas most asteroids vary in brightness by 10 to 20 percent as they spin, ‘Oumuamua changed by an unprecedented factor of 10, suggesting an extraordinary needlelike shape that sometimes presented a large and bright surface and sometimes showed only a very narrow edge.
The object’s resemblance in size and proportions to a large rocket—for example, the Saturn V, which measures about 110 meters by 10 meters—was hard to ignore. Indeed, discarded rockets orbiting the sun are occasionally rediscovered by astronomers surveying the sky for asteroids and comets, as was the case for 2000 SG344, a likely Apollo-program relic discovered in 2000. But the orbit of ‘Oumuamua was too extreme for it to be a rocket from the 1960s. Could it be a rocket from another civilization? Incredible as it sounds, scientists could not immediately reject the possibility based on the available data.
While astronomers were pondering this conundrum, they got another surprise. In June 2018 Italian astronomer Marco Micheli of the European Space Agency and his colleagues reported measurements of the shape of ‘Oumuamua’s orbit, which revealed the action of a weak, rocketlike force pushing on the body in addition to the gravitational forces of the sun and planets.
So-called nongravitational forces are well known to exist in comets, arising from the asymmetric push of ices sublimating from the dayside of the comet’s core. But ‘Oumuamua is not a comet. And it showed no evidence that it was losing mass at all, which could have explained the force. Could it be that ‘Oumuamua emitted only gas, which is harder to detect than comet dust? Possibly, but it would make ‘Oumuamua unique: astronomers know of no other cosmic object that lets off gas but no dust or ice. Micheli suggested that ‘Oumuamua might eject very large dust particles that were invisible to our telescopes.
In November 2018 Shmuel Bialy of the University of Maryland and Avi Loeb of the Center for Astrophysics | Harvard & Smithsonian proposed that the nongravitational force could be caused by sunlight, which exerts a weak pressure on any object placed in its path. To experience enough radiation pressure that we could measure it, however, ‘Oumuamua would have to be either extraordinarily thin like a sheet of Mylar (the aluminized plastic used to make birthday balloons) or of very low density. Bialy and Loeb suggested that the object could be a “light sail,” a flat, sail-shaped vehicle sent from another civilization and designed to be pushed through space by starlight.
As intriguing as that idea may be, most astronomers favor a natural origin for ‘Oumuamua. In February 2019 one of us (Moro-Martín) calculated that for ‘Oumuamua to be propelled by sunlight, it would have to be 100 times less dense than air. Such a cosmic dust bunny—an “icy fractal aggregate”—might have grown in the outer parts of the protoplanetary disk of another star, where baby planets congeal out of ice and dust rubble. In the summer of 2020 Luu, Eirik FlekkØy and Renaud Toussaint, then all at the University of Oslo, proposed that ‘Oumuamua grew from a collection of dust particles in the coma of an active comet, then escaped. This type of material is unknown on Earth but could conceivably survive in the ultimate vacuum of interstellar space.
Given how odd ‘Oumuamua is, what might be most incredible of all is that objects like it must be common. We know that this relatively tiny body was detected only because it passed close to Earth and that humans have had the capability to see such an object for only a few years (the Pan-STARRS facility began operating in 2010 but reached full efficiency almost a decade later). Based on statistics alone, these two facts allowed scientists to estimate that the number of similar interstellar interlopers per unit volume of space is about one per 10 cubic AU (one AU, or astronomical unit, is the distance between Earth and the sun). Thus, in the planetary region of our solar system, defined as a sphere with the radius of Neptune’s orbit, there must be about 10,000 similar objects, of which ‘Oumuamua was only the first one close enough to be detected in the operational lifetime of Pan-STARRS. If these objects take about a decade to cross the planetary region, the average rate of interloper arrivals must be about three a day!
What, then, does this frequency suggest about the origin of ‘Oumuamua? Aliens might be capable of sending a Saturn V–size rocket or a large piece of Mylar-like material across the galaxy and through our solar system, but why would they send so many? Even more astonishing, if we extrapolate our analysis from the solar system to the whole of the Milky Way, we find that there must be 1 × 1024 to 1 × 1025 (a trillion trillion to 10 trillion trillion) similar objects in our galaxy. It is hard to believe that an extraterrestrial civilization would have the capacity to flood the galaxy with so much space junk, and it is even more difficult to see why it would do so. Thus, given the maxim that extraordinary claims require extraordinary evidence, most astronomers think ‘Oumuamua is just a weirdly shaped, but natural, piece of debris from elsewhere in the galaxy.
Credit: Matthew Twombly; Source: Small-Body Database Browser, Jet Propulsion Laboratory/NASA (trajectory)
A Second Discovery
The sheer strangeness of ‘Oumuamua left astronomers eagerly awaiting the discovery of the second interstellar interloper. Would the next one be as peculiar, or would it look like a regular solar system comet or an asteroid without nongravitational motion?
Without knowing the answers to these questions, we predicted that the second object would arrive within a year or two, based on the estimate that there must be about one body like ‘Oumuamua per 10 cubic AU. To our delight, two years after ‘Oumuamua, Ukrainian amateur astronomer Gennadiy Borisov discovered C/2019 Q4 using a homemade telescope; it was soon renamed 2I/Borisov—the second interstellar object. It has an orbit even more extreme than that of ‘Oumuamua, but it appears to be a rather ordinary comet. Measurements from the Hubble Space Telescope showed that its nucleus is larger than ‘Oumuamua, with a radius between 0.2 and 0.5 kilometer. In contrast to ‘Oumuamua, 2I/Borisov displays no extreme light curve, and its nongravitational motion is simply a consequence of asymmetric outgassing as ice comes off its surface, just as in solar system comets. In March 2020 it briefly flared in brightness and then took on a doubled appearance as a small piece of the nucleus detached, something commonly observed with solar system comets. In other words, this body is pretty much exactly what we would have expected an interstellar object to be like.
Our expectations are based on theories of planet formation, which suggest a ready mechanism for kicking some objects out of their home planetary systems and into the galaxy, where they may eventually make their way to our little corner of the cosmos. Studies suggest that planet formation begins in an orderly way but ends in a chaotic mess. The sun, for instance, was born 4.6 billion years ago in a flattened, rotating disk that grew as a giant molecular cloud contracted under its own gravity. This disk of gas, ice and dust feeding the nascent star in its center was very dense, which allowed tiny grains to collide and stick to one another. At first pebbles formed, then larger bodies known as planetesimals and, eventually, the planets. Some of the planetesimals escaped further growth and heating when they were scattered to the outer solar system shortly after they formed. There, in deep freeze, they have remained mostly unaltered ever since.
Sometimes, though, these bodies get scattered back into the inner system, where the sun’s heat causes their ice to sublimate; they develop tails of ejected material, and we call them comets. Other planetesimals are expelled from the system entirely, destined to spend eternity drifting among the stars. Once lost in the vastness of the Milky Way, such an object has a negligible chance of reentering the planetary system it came from, but it could certainly be deflected by the gravity of an alien star. Given the chaos of this process and the numerous encounters ‘Oumuamua and Borisov must have had before they reached us, we will likely never know precisely how long these objects have been adrift or determine with confidence where they came from.
Nevertheless, we can feel confident that Borisov is an ice-rich planetesimal from the outer regions of the planet-forming disk of an unknown star. In fact, everything we have learned about Borisov—and the proof it offers that some interstellar objects look much like we expected—puts the strangeness of ‘Oumuamua in stark relief. Given the extraordinary differences between the two, there is no reason to assume that they share a common origin.
Astronomers are still trying to puzzle out what ‘Oumuamua is, and new ideas come up often. One suggestion, proposed in May 2020 by Darryl Seligman of the University of Chicago and Gregory Laughlin of Yale University, is that ‘Oumuamua is a novel type of body made of molecular hydrogen ice—a cosmic iceberg that originated in the coldest regions of a molecular cloud. In June 2020, however, Loeb and Thiem Hoang of the Korea Astronomy and Space Science Institute argued that molecular hydrogen is so volatile that such a body could neither have formed in a molecular cloud nor have survived interstellar travel. Another option, put forward in April of that year by Yun Zhang of the National Astronomical Observatories of the Chinese Academy of Sciences and Douglas N. C. Lin of the University of California, Santa Cruz, is that ‘Oumuamua might instead be shrapnel produced by gravitational shredding of a planet or other body passing too near its parent star.
‘Oumuamua’s strange properties aside, the fact that the object was detected at all runs counter to the conventional wisdom about planetary system formation, which suggests that interstellar visitors should be very rare. We can estimate the number of interstellar planetesimals we expect to exist per unit volume of space based on the observed number of stars and on our knowledge of star and planet formation, stellar evolution and dynamics. The calculation involves many uncertainties, but a generous upper limit is at least a tenth to a hundredth the size of the previously mentioned statistical frequency estimate of 10,000 such objects in the planetary region. Put simply, we cannot account for that much litter in the galaxy. Perhaps as we detect more interlopers and understand them better, the inferred and estimated values of their space density will start to converge. But it is also possible that we are missing an important source of interstellar objects—maybe some process in space other than the planetesimal scattering we have described creates bodies that find their way to us.
Credit: Matthew Twombly; Source: Small-Body Database Browser, Jet Propulsion Laboratory/NASA (trajectory)
Lifeboats from Beyond
Besides teaching us about how planetary systems form, the discovery of interstellar visitors may have a bearing on one of the most fundamental mysteries in science: How did life on Earth begin? One idea, called panspermia, is that the seeds of ancient organisms hitched a ride on asteroids hailing from other systems.
Just as we expect interstellar bodies to enter our solar system occasionally, we must also assume that they sometimes hit our planet. Based on the value of one object per 10 cubic AU that we inferred from the detection of ‘Oumuamua and 2I/Borisov, we can estimate that similar objects strike about once every 100 million to 200 million years, thousands of times less frequently than asteroids of comparable size. Most would probably detonate and disperse in the atmosphere, but a few would actually reach the ground. Scientists estimate that over the eons several billion tons of interstellar material must have crashed into Earth.
Could these impacts have delivered life to our planet? The modern scientific notion of panspermia dates back to the 19th century. Surprisingly, asteroids and comets might be good protectors of fragile cellular life. Damaging cosmic rays, capable of breaking DNA, penetrate only a few meters into solid material, so living cells buried inside rocks might survive interstellar journeys lasting millions or even hundreds of millions of years. At near-zero interstellar temperatures, any cells would be in suspended animation. They would need to withstand the shock of planetary impact, but this might not be as problematic as it sounds. Experiments have already shown that earthly bacteria can survive impacts at cosmic speed. Although there is no evidence that life spreads through the galaxy while riding in the bellies of asteroids and comets, given our present state of ignorance, we must acknowledge that this possibility remains.
To improve our understanding of interstellar objects, we need to find more examples. Currently, with only two to go on, our grasp is limited. Fortunately, new developments in astronomy make it very likely that we will soon observe dozens of similar objects, and those discoveries will allow us to better pin down the statistics and to understand their physical properties. Most professional telescopes have very small fields of view, often only a few thousandths of the area of the full moon. But optics and large detectors are now capable of capturing the whole moon and more in a single shot and the entire sky in a night or two of continuous scanning. Powerful computers make it possible to compare successive all-sky scans to find moving objects, including interstellar interlopers.
Having a larger sample of interstellar objects will help us answer many questions about the objects themselves. How many interlopers are strangely iceless and oblong like ‘Oumuamua versus akin to a comet like 2I/Borisov? Are there bigger examples? Are there smaller ones? What are they made of? Are some really porous enough to be pushed around by the pressure of light? New data from the Rubin Observatory, now under construction on a Chilean mountaintop, should provide fresh insights. The Rubin telescope has a collecting mirror 8.4 meters in diameter and a three-billion-pixel detector that would have been unthinkable just a decade ago. Each image from this gigantic camera will cover an area 40 times that of the moon, an enormous advance. It will also systematically survey the sky more deeply than has ever been attempted and on a repeated basis. This new facility is expected to reveal interstellar interlopers in abundance, along with vast numbers of asteroids, comets and Kuiper belt objects from our own solar system.
To truly understand the nature of any given interloper, we would like to send a spacecraft to visit it or even land on it. One practical problem is that there is not much time to make plans because these objects move so fast. ‘Oumuamua faded to invisibility for even the largest telescopes within months of its discovery. 2I/Borisov was expected to become too faint to detect within a few years. For comparison, space missions often take a decade or more, including their design, approval, construction and launch, making it impossible to plan for any particular interstellar target. A solution might be to send the spacecraft into a storage orbit before knowing where the mission will go. This is the idea behind the European Space Agency’s Comet Interceptor, due to be launched in 2029. The Interceptor will park at Earth’s L2 Lagrangian point 1.5 million kilometers away, where it can easily maintain a stable orbit as it awaits the flyby of an interesting object. The Interceptor lacks the power to rendezvous with an interloper unless one happens by chance to pass very close to L2, however.
More capable rockets are intrinsically heavy and expensive to launch; even if a flyby is possible, accelerating to hyperbolic orbit speed to grab a sample will not be easy. Spacecraft powered by novel propulsion methods, such as light sails accelerated by a laser beam from Earth or by solar radiation pressure, are another option, but they involve difficulties of their own. Still, the prospect of being able to closely examine an object that unequivocally originated beyond our solar system is extraordinary, and scientists have not been shy in proposing ways to do so. One way or another, we will pry the secrets from our interstellar visitors.