In October 2020, a small spacecraft briefly touched down on an asteroid to snag a piece of it to bring to Earth. Almost two years later, scientists have learned that if the OSIRIS-REx spacecraft had extended its stay even a tiny bit longer, it would have sunk right into the asteroid.
That’s because asteroid Bennu is nothing like scientists had predicted. Rather than being a solid, flying rock, Bennu is actually made up of small, pebble-like particles that are not strongly bound together, creating lots of space on its surface. It’s most comparable to a plastic ball pit, NASA writes in a new release. “Our expectations about the asteroid’s surface were completely wrong” Dante Lauretta, principal investigator of OSIRIS-REx and lead author of a recent paper detailing the findings, said in the release.
OSIRIS-REx arrived at the asteroid in December 2018 with a mission to retrieve a sample from Bennu and carry it to Earth for analysis. The spacecraft touched down on Bennu in October 2020, extending its robotic arm to scoop up a piece of the asteroid. OSIRIS-REx then immediately fired up its thrusters to back away from Bennu. The spacecraft’s sampling head touched Bennu’s surface for approximately 6 seconds before retreating. By stirring up some of the dust and pebbles on the asteroid, OSIRIS-REx was able to grab a couple ounces of material.
OSIRIS-REx Sample Collection at Asteroid Bennu: SamCam View of TAGSAM
The brief rendezvous left quite an impression on Bennu, resulting in a chaotic explosion of pebbles and a crater 26 feet (8 meters) wide. “Every time we tested the sample pickup procedure in the lab, we barely made a divot,” Lauretta said. But after reviewing the footage from the real sample pick-up, the scientists were left confused. “What we saw was a huge wall of debris radiating out from the sample site,” Lauretta said. “We were like, ‘Holy cow!’”
After analyzing the volume of debris seen in before-and-after images of the landing site, the scientists learned that OSIRIS-REx faced as much resistance from touching down on the asteroid as “a person would feel while squeezing the plunger on a French press coffee carafe,” NASA wrote in a statement. That is to say, the spacecraft met very little resistance, certainly not the type of resistance one would expect from landing on a rocky body. As the spacecraft fired its thrusters to depart, it was sinking into the asteroid.
“If Bennu was completely packed, that would imply nearly solid rock, but we found a lot of void space in the surface,” Kevin Walsh, a member of the OSIRIS-REx science team and lead author of a second paper on Bennu’s composition, said in a statement.
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When OSIRIS-REx first arrived at the asteroid, closeup images of Bennu revealed that its surface was filled with boulders, rather than the smooth sandy surface that had been predicted. The images also showed that Bennu was spitting out pebbles into space. “I think we’re still at the beginning of understanding what these bodies are, because they behave in very counterintuitive ways,” Patrick Michel, an OSIRIS-REx scientist, said in the NASA release.
Bennu has been full of surprises. One of the first was its odd shape, similar to a child’s spinning top.
The DART mission will be the first to test asteroid deflection through kinetic impactor technology. Illustration: NASA
In order to protect the Earth, some sacrifices must be made. NASA’s DART spacecraft is currently on its way to a binary asteroid system known as Didymos and will essentially crash into one tiny asteroid to test out a deflection method. But rather than leaving behind an impact crater as initially intended, the DART spacecraft may actually deform the mini-moon, making it nearly unrecognizable.
Using a new model, a group of researchers have simulated the entire cratering process and discovered that the asteroid deflection mission might completely alter its target, changing its appearance far more severely than previously believed.
“The DART impact could globally deform Dimorphos, and therefore change its overall shape significantly, instead of creating just a small crater,” Martin Jutzi, co-author of the study, which was published in The Planetary Science Journal, told Gizmodo in an email.
This illustration shows the possible shapes that the asteroid might take following impact.Illustration: Courtesy of Martin Jutzi
As seen in the above illustration, the mini-moon, dubbed Dimorphos (formerly known as Didymoon), could take on one of these six possible shapes following the spacecraft’s impact. The whole cratering process could take a few hours, which is why previous models of the impact did not predict the asteroid’s subsequent deformation. “Previous models were only able to simulate the first seconds of such events,” Jutzi said.
Short for Double Asteroid Redirection Test, the DART mission launched in November 2021 towards the Didymos asteroid system. Didymos is an 800-meter wide rock with its own 170-meter wide moon known as Dimorphos, the main target of DART. The spacecraft will smash into the mini-moon at 15,000 miles per hour (24, 140 kilometers per hour), attempting to offset its orbit. The impact is scheduled for late September or early October, when the pair will come within 7 million miles (11 million kilometers) of Earth.
The purpose of the test is to experiment with kinetic impactor technology as a means of deflecting asteroids that could be headed towards Earth. NASA and other space agencies, keep a close watch on asteroids that come too close for comfort in order to assess whether or not they pose a threat to our planet. But as far as defending Earth from incoming asteroid impacts, there’s no clear cut plan on what to do.
“These weak asteroids could actually be deflected much more strongly and larger amounts of material could be ejected from the impact than the previous estimates predicted,” Jutzi said. “These larger effects should be easier to observe immediately after the DART impact.” So the DART mission will still be able to perform the experiment, just perhaps with a different outcome than initially anticipated.
The European Space Agency (ESA) is also planning a follow-up mission to the pair of space rocks. ESA is scheduled to launch its Hera mission in 2024, which will rendezvous with Didymos by 2026 to study the impact crater left behind by DART, and any other changes made to the asteroid. If Dimorphos has indeed taken on a different appearance, it may provide valuable data on the asteroid itself.
“Ideally, this will allow us to learn something about the asteroid’s interior, rather than just the surface,” Jutzi said. “This would in turn provide very valuable information about the asteroid’s bulk properties and improve our understanding of asteroids in general.”
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Artist’s impression of Dimorphos shortly after being struck by NASA’s DART spacecraft. China’s proposed kinetic impaction test would likely use a similar strategy. Image: ESA
The global effort to protect Earth from dangerous asteroids is set to become stronger, as China has announced its intentions to test an asteroid redirect system as early as 2025.
Speaking to China Central Television on Sunday, Wu Yanhua, deputy head of the China National Space Administration (CNSA), described China’s preliminary plans to embark on the planetary defense project, according to Chinese state-owned news agency Global Times. Wu’s comments coincided with Space Day, an annual event that commemorates the 1970 launch of China’s first satellite, Dongfanghong-1, in 1970.
For the proposed test, Wu said a probe would closely survey a near-Earth object prior to smashing into it. Known as kinetic impaction, the idea is to alter the orbital trajectory of a threatening asteroid by directing a large, high-speed spacecraft into the object. NASA is currently running a similar test, known as the Double Asteroid Redirection Test, or DART, which seeks to deliberately crash a space probe into Dimorphos—a tiny asteroid—later this year.
The Global Times says the CNSA project is in its infancy and is still being reviewed for approval. The Chinese space agency is targeting 2025 or 2026 to conduct the test, a timeline that coincides with the end of China’s 14th Five-year plan period, according to Wu.
In addition, Wu said the CNSA hopes to develop a ground-based monitoring and warning system to analyze and catalog potentially dangerous near-Earth objects. No further details were given, but the system will likely emulate NASA’s Sentry-II monitoring system, which autonomously evaluates asteroid impact risks. Software designed to simulate the risks posed by asteroids and tabletop exercises to rehearse the defense process are also planned, according to the Global Times, adding that China is “shouldering the responsibility as a major global power in safeguarding the Earth with other countries.” The proposed monitoring and warning system would precede the asteroid mitigation test, Wu said.
Having more eyes on the sky is a good thing. My hope is that CNSA, NASA, and other space agencies and astronomical groups will pool their resources to make sure no threatening asteroids are missed and to coordinate these efforts in meaningful ways. NASA says it’s currently tracking 28,000 near-Earth objects and that roughly 3,000 are being added to the list each year.
The proposed CNSA program and kinetic impaction test is welcome news and another sign of China’s ongoing ambitions in space and space exploration. The country’s space-based initiatives are advancing quickly, as evidenced by its robotic lunar and Martian missions and its nascent space station, which is being made available to foreign astronauts, including space tourists.
Artist’s impression of Comet Bernardinelli-Bernstein.Image: NOIRLab/NSF/AURA/J. da Silva (Spaceengine)
Bernardinelli-Bernstein is officially the largest comet ever discovered, according to updated observations of the inbound object.
Oort Cloud comet C/2014 UN271, also known as Comet Bernardinelli-Bernstein, measures some 85 miles (137 km) in diameter, give or take 10.5 miles (17 km), reports a research team led by astronomer Emmanuel Lellouch of the Paris Observatory. Their new paper on the mega comet has been accepted for publication in Astronomy and Astrophysics Letters, and you can sneak a peak of the preprint at the arXiv.
These latest observations confirm that Comet Bernardinelli-Bernstein is the largest Oort Cloud object ever detected, as it’s nearly twice as big as comet Hale-Bopp (observed in 1997), the nucleus of which measured between 25 and 50 miles (40 and 80 km) wide. It’s also bigger than Comet Sarabat (observed in 1729), which had a nucleus measuring somewhere around 62 miles (100 km) in diameter.
Comet Bernardinelli-Bernstein is currently inbound from the Oort Cloud, a distant region of the solar system known for packing billions and possibly trillions of icy objects. The comet will make its closest approach to Earth in 2031, when it will come to within 11 au of the Sun (1 billion miles), in which 1 au is the average distance from Earth to the Sun. The comet, coming no closer than Saturn, won’t likely be visible to the unaided eye, but astronomers will be keeping a close watch, as it’s turning out to be a rather extraordinary object.
Named after its discoverers, Pedro Bernardinelli and Gary Bernstein from the Dark Energy Survey, the comet is special for several reasons. Astronomers first detected the inbound object when it was still very far away—some 29 au from the Sun (2.7 billion miles). That’s as far out as the orbit of Neptune, but astronomers didn’t appreciate its significance until it came to within 24 au of the Sun (2.2 billion miles), at which time it began to display distinctive cometary activity. Researchers with Las Cumbres Observatory confirmed its cometary nature in June 2021. Its remarkable brightness indicated an object of enormous size, with preliminary estimates pointing to an object between 62 and 230 miles (100 and 370 kilometers) wide.
For the new study, Lellouch and his colleagues used the Atacama Large Millimeter Array (ALMA) in Chile to refine the comet’s size and reflectivity, or albedo. They did so on August 8, 2021, when Bernardinelli-Bernstein was 20 au from the Sun (1.86 billion miles). The team honed in on microwave radiation leaking out from the comet’s nucleus, while taking care to exclude radiation produced by the surrounding cloud of dust.
These thermal emissions pointed to the 85-mile (137 km) diameter, with a lower bound of 75 miles (120 km) and an upper bound of 96 miles (154 km). The large error bar is on account of uncertainties having to do with the object’s shape and reflectivity. Future observations should refine these estimates further.
The estimated albedo of 5.3% now represents the most distant measurement yet of a comet’s reflectivity. With the size of the nucleus now better defined, astronomers will be able to measure how much material the comet will lose during its trip around the Sun.
Bernardinelli-Bernstein is not the 230-mile behemoth suggested by preliminary measurements, but it’s still gigantic. As it nears the Sun, volatiles on its surface, especially ice, will increasingly sublimate, turning directly from solid into gas. This could give the comet a distinctive coma and tail, but we’ll have to wait a few more years to know for sure. We’ll be watching.
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If you’re a fan, like I am, of not being crushed to death by a rock that falls from the sky, then you should be interested in the mission NASA launched today with a SpaceX Falcon 9 rocket. The spacecraft in the nose of that rocket is called DART (Double Asteroid Redirection Test), and that spacecraft is going to smack right into the asteroid Dimorphos in hopes of redirecting its path.
Now, I’m happy to say this is being done not because Dimorphos is actually threatening to hit the Earth but because it makes for a good test subject. See, Dimorphos is part of a binary pair of asteroids and orbits around the asteroid Didymos, so NASA can tell if the impact of DART into Dimorphos affected its orbit around Didymos. It can then use that information to calculate how a similar strike to an asteroid potentially headed to Earth could be deflected.
The spacecraft is small and boxy, and it will hit Dimorphos at an impressive 14,760 mph, sped along by its NEXT xenon ion thruster engine, which converts solar energy into gradual but persistent thrust.
Illustration: NASA
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An onboard camera and autonomous navigation software will guide DART to its self-sacrifice into the asteroid, which will change the speed of the asteroid’s orbit around the main asteroid by a fraction of a percent. But that should affect the orbital period by several minutes, all of which will be confirmed by observations from Earth.
Illustration: Ted Lopez / Johns Hopkins APL
DART won’t arrive at the asteroid pair until next September or so, which means you have plenty of time to figure out how to get close if you want a ringside seat.
The ability to deflect an asteroid could one day prove to be absolutely crucial to the safety of everything living on Earth. While, so far, NASA does not predict an asteroid of significant size hitting Earth in the next century or so, there have been 1,200 meteor impacts to Earth from asteroids over three feet in length since 1988, and only 0.42 percent of those—five—were actually predicted in advance.
So, it’s not exactly like we have a really solid handle on this whole asteroid-prediction thing, and figuring out a way to be ready to deflect something would really be a great idea. Ideally, if this test works, a similar deflecting spacecraft will be made available and be ready to go, should the situation arise in the future.
Asteroids come in all shapes and sizes; some are large enough to earn the title of dwarf planet, while others are about ostrich-sized. These wandering rocks are incredibly important objects for scientists seeking information about the formation of the solar system and even life on Earth. Some meteorites (the space rocks that fall to Earth) contain amino acids, and plenty of asteroids contain evidence that they once carried water. The history of life on Earth could be chalked up to a couple lucky fallen rocks, in theory.
We’ve visited only a few asteroids to date, but NASA is working on changing that. The recently launched Lucy spacecraft is set to explore Jupiter’s Trojan asteroids, a mission that will bring us a whole new understanding of these strange objects. But until Lucy gets to its first targets, we’ll have to keep ourselves busy with the space rocks we’ve already seen up close.
Though not as massive or colorful as planets, asteroids have a lot to teach us about our local corner of the universe. That’s especially the case for asteroids close enough to be sampled—such as Bennu was in October 2020—or when rocky fragments fall to Earth as meteorites.
Asteroids are the detritus left over from the creation of our solar system’s planets, and as such, they contain information about what things were like billions of years ago. NASA has counted over 1 million asteroids to date, and recently, the Very Large Telescope at the European Southern Observatory imaged 42 of the largest ones.
“Only three large main belt asteroids, Ceres, Vesta and Lutetia, have been imaged with a high level of detail so far, as they were visited by the space missions Dawn and Rosetta of NASA and the European Space Agency, respectively,” said Pierre Vernazza from the Laboratoire d’Astrophysique de Marseille in France in an ESO press release. Vernazza led a study on the asteroids published today in Astronomy & Astrophysics.
The Very Large Telescope makes observations in visible and ultraviolet light. It is actually made up of four unit telescopes, all of which sit high up in Chile’s Atacama Desert, one of the best places for looking at the sky. The images were taken using the SPHERE instrument on the telescope, which ordinarily does direct imaging of exoplanets, but in this case was able to get a great look at a number of asteroids in the main belt.
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The recent work by Vernazza’s team improves the quality and quantity of images detailing asteroids’ sizes and structures. These images will help astronomers get better understanding of the solar system’s origin.
The asteroids range from the very dense ones, like Kalliope and Psyche, to some of the least dense, like Sylvia and Lamberta. The smallest two asteroids in this group are Ausonia and Urania, which each measure about 55 miles wide. The largest asteroid, Ceres, is 584 miles across, large enough that it is considered a dwarf planet.
All of these objects offer insights about the primordial soup that forged them; for example, the research team found that the least dense asteroids of the 42 most likely formed farther out than their denser brethren, somewhere beyond the orbit of Neptune, and eventually migrated inward to their current locations.
“Our observations provide strong support for substantial migration of these bodies since their formation. In short, such tremendous variety in their composition can only be understood if the bodies originated across distinct regions in the Solar System,” said Josef Hanuš of the Charles University in Prague and one of the authors of the study, in the ESO release.
And if you’re impressed by the Very Large Telescope, just wait until the Extremely Large Telescope becomes operational later in the 2020s. That telescope will gather 20 times more light than a unit of the Very Large Telescope, allowing astronomers to see fainter objects better than they currently can. (Alas, the Overwhelmingly Large Telescope never made it past the concept phase.)
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Bennu, as imaged by OSIRIS-REx.Image: NASA/Goddard/University of Arizona
Data gathered during the years NASA’s OSIRIS-REx spent zipping around asteroid Bennu has allowed scientists to update the risk posed by this potentially hazardous near-Earth object.
The spacecraft OSIRIS-REx is currently en route to Earth, carrying surface samples it collected from asteroid Bennu. From December 2018 to May 2021, the NASA spacecraft studied the gigantic rubble pile from every angle, measuring its size, shape, mass, composition, spin, orbital trajectory, and other important characteristics. Bennu is a primitive carbonaceous asteroid, so by studying this object, scientists can make inferences about what our solar system was like during its formative period.
But there’s more to this $800 million mission than just looking for organic molecules or signs of water and heavy elements. Bennu is currently ranked second on the list of potentially dangerous asteroids, highlighting the importance of learning as much as we can about it—especially the orbital dynamics that dictate its future movements.
The new research, published in Icarus, does exactly this, providing a refined trajectory of Bennu through to the year 2300. The misanthropes among you may be pleased to learn that Bennu still has a very slight chance of hitting our planet next century. The odds of a collision through the year 2300 remain very low, however: They’re now pegged to be about 1 in 1,750, or 0.057%.
Data derived by OSIRIS-REx, NASA’s Deep Space Network, and computer models allowed the scientists to constrain uncertainties in Bennu’s orbit by a factor of 20. OSIRIS-REx is what really made this possible, as it measured Bennu’s position relative to Earth down to the scale of a few meters.
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Speaking earlier today at a teleconference held for reporters, Davide Farnocchia, the lead author of the new paper and a researcher with the Center for Near Earth Object Studies at NASA’s Jet Propulsion Laboratory in Southern California, said it’s an “impressive” result, as “we had one of the best known orbits in the entire asteroid catalogue,” in reference to Bennu. Dante Lauretta, a co-author of the study and OSIRIS-REx principal investigator at the University of Arizona, said this “incredible precision” allowed the team to characterize the asteroid’s orbital parameters and better predict where it’ll be in the future.
Impressively, the new model allowed the researchers to eliminate 24 of 26 possible keyholes for Bennu that were predicted to exist on September 11, 2135, when the asteroid is scheduled to safely zip past Earth. Gravitational keyholes can be likened to fictional gateways that take characters into alternative timelines (fans of the new Loki series know what I’m talking about). Keyholes are very much real, however, and they’re bad news—we don’t want asteroids to pass through keyholes, as they’re gateways that take asteroids onto orbital trajectories that threaten Earth.
There’s no chance of an impact during this encounter in 2135, said Farnocchia, but Bennu will be close to Earth—about half the distance from Earth to the Moon—and this will change the asteroid’s trajectory. To know this change in trajectory, however, scientists have to consider gravitational keyholes.
As NASA describes them, keyholes are “areas in space that would set Bennu on a path toward a future impact with Earth if the asteroid were to pass through them at certain times, due to the effect of Earth’s gravitational pull.” The new research describes two keyholes still in play, including one that would involve a collision between Earth and Bennu on September 24, 2182 (mark your calendars), but the probability is slim, at 1 in 2,700, or 0.037%. As Farnocchia reminded reporters repeatedly during the press conference, “there’s no reason for concern.”
The reason for so much uncertainty has to do with all the variables in play. Sir Isaac Newton described a universe that works with clock-like precision, but the clock that is our solar system features an unspeakable number of moving parts. These perturbing influences include things like the Sun’s gravity, the planets, all the moons, hundreds of asteroids, interplanetary dust, and the solar wind.
For the new study, Farnocchia and his colleagues tried to account for as many variables as possible to predict Bennu’s future trajectory, including the masses of 343 known asteroids. They even accounted for a possible nudge exerted by OSIRIS-REx when it grabbed a sample of surface material on October 20, 2020 (it turned out to be negligible) and bits of debris that are naturally falling from Bennu (also not a factor).
There’s also the Yarkovsky effect to consider. This is what happens when an object absorbs radiation from the Sun and this radiation then leaks away. This alters an object’s momentum in space, causing it to drift slightly from the path otherwise dictated by gravity. This effect is very slight, but it becomes meaningful over vast timescales. OSIRIS-REx gathered invaluable information—information that’s hard if not impossible to collect from the ground—that was used to calculate the Yarkovsky effect as Bennu travelled around the Sun, including the object’s size, mass, shape, rotation, surface properties, and other factors, as Farnocchia explained. This “helped us to model the future motion of Bennu,” he added.
Interestingly, the samples collected by OSIRIS-REx could further our understanding of how the Yarkovsky effect might continue to change Bennu’s trajectory. Analysis of the surface samples could “expose changes to the asteroid over time, like surface weathering,” which would “further our understanding of one of the most important parameters for determining orbital trajectory,” as Lauretta explained in response to a question posed by yours truly.
The new research provides the most solid estimates of Bennu’s future to date, but there’s still room for improvement. The researchers would like to account for the gravitational influence of all the asteroids in the solar system; determining the mass of these asteroids would be “a major next step forward,” said Farnocchia. Improved measurements of Bennu’s mass and density, which are still uncertain, would also help. Bennu is a loose pile of rocks and dust that probably features empty cavities and an uneven distribution of materials beneath the surface.
And now we wait for September 24, 2023, when OSIRIX-REx is set to return to Earth with its samples. Lauretta said the mission is in “great shape right now,” which is obviously good news. There’s still much to learn about this fascinating—and possibly worrisome—asteroid.
Normally, NASA likes its probes to make contact with other objects in space in a very controlled manner. You want to land a rover on Mars, not drop a rover on Mars, for example. The Double Asteroid Redirection Test (DART) is different. This time, NASA is going to stomp the ion pedal and just ram the damn thing with their spaceship, because fuck you, asteroid. Also, they’ll learn a lot about potentially diverting dangerous asteroids from becoming meteors that hit Earth. But mostly because they don’t like how that asteroid is looking at them.
Image: NASA
You know the DART project is exciting because it’s in the Planetary Defense section of the NASA website, which sounds like part of a movie involving lasers and at least one astronaut tumbling away into space.
The DART spacecraft is a boxy, ion-engined kinetic impactor with interesting roll-out solar panels, and looks like this:
Image: NASA
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The ion engine is especially interesting, because it’s a first application of a propulsion system likely to be used on future spacecraft:
“The DART spacecraft will demonstrate the NASA Evolutionary Xenon Thruster – Commercial (NEXT-C)solar electric propulsion system as part of its in-space propulsion. NEXT-C is a next-generation system based on the Dawn spacecraft propulsion system, and was developed at NASA’s Glenn Research Center in Cleveland, Ohio. By utilizing electric propulsion, DART could benefit from significant flexibility to the mission timeline while demonstrating the next generation of ion engine technology, with applications to potential future NASA missions.”
The target asteroid is an interesting choice, because it’s really two asteroids. The asteroid is called Didymos, and is a binary asteroid, because it has its own little “moonlet,” a smaller asteroid that orbits Didymos. This moonlet is DART’s target.
Image: NASA
Using the solar-powered ion engine and advanced autonomous targeting software, DART will ram itself into the moonlet, which will change the speed of the moonlet’s orbit around Didymos, a change that can be studied by telescopes on Earth.
Image: NASA
Studying the change in the orbital path can help us figure out how to most effectively smack a potential Earth-impacting asteroid off course enough to miss our planet, where we not only keep our stuff, but is also the location of every Shake Shack known to humankind.
Also, like any good, modern fight, there will be a witness getting the whole thing on video, in this case a small Cubesat that will be released prior to impact and may or may not upload the footage to Worldstar.
Over at Vice, there’s a good interview with astronomer Andy Rivkin who gives a great explanation of the DART mission and what it hopes to accomplish:
So, yeah, take that, asteroid. That little punk moonlet has until November 24 to February 15 of 2022 to get its shit together, since that’s the current launch window for DART.
Apophis as it was imaged during its most recent flyby. Image: NASA/JPL-Caltech and NSF/AUI/GBO
Asteroid Apophis—one of the scariest rocks in the solar system—won’t pose a threat to Earth for at least another century, according to updated NASA calculations.
Every 80,000 years or so, an object measuring around three football fields in length smashes into Earth, unleashing the equivalent of over 1,000 megatons of TNT. The discovery of Apophis in 2004 fit the description of one of these once-in-80,000-year events, understandably freaking a lot of people out. A hit from Apophis wouldn’t be Chicxulub bad—the 10-mile-wide (16-kilometer) asteroid that wiped out most life on the planet some 66 million years ago—but it’d inflict catastrophic levels of local damage and trigger a global-scale impact winter.
In 2004, astronomers detected asteroid 99942 Apophis, a near Earth object measuring around 1,100 feet (340 meters) long. Its status as a potentially hazardous object has been continually refined over the years, but 2068 continued to represent a particularly worrisome year for the asteroid to hit us.
We can now breathe a sigh of relief, however, as the latest calculations suggest the asteroid won’t pose a threat to Earth for the time being, according to a NASA statement. A recent flyby of Apophis, in which the asteroid came to within 44 times the distance of Earth to the Moon, allowed NASA to refine its measurements, resulting in the new assessment.
“A 2068 impact is not in the realm of possibility anymore, and our calculations don’t show any impact risk for at least the next 100 years,” Davide Farnocchia of NASA’s Center for Near-Earth Object Studies explained in the space agency’s announcement.
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As a consequence, NASA has now removed Apophis from its naughty list, otherwise known as the Sentry Impact Risk Table. This table, maintained by CNEOS, had ranked Apophis as the third most dangerous known object, assessing an impact probability at around 1 in 150,000. The odds were slim but undeniably nonzero. The new calculations have allowed CNEOS to remove Apophis from the risk table altogether.
“With the support of recent optical observations and additional radar observations, the uncertainty in Apophis’ orbit has collapsed from hundreds of kilometers to just a handful of kilometers when projected to 2029,” said Farnocchia. “This greatly improved knowledge of its position in 2029 provides more certainty of its future motion, so we can now remove Apophis from the risk list.”
The year 2029 is notable because that’s the next time Apophis will fly past Earth, during which time it’ll seriously invade our personal space. It will come to within 20,000 miles (32,000 km) of our planet, which is a tenth the distance of Earth to the Moon and within the reach of some satellites. Apophis will be so close that it’ll be visible to small telescopes and binoculars.
When Apophis flew past Earth in early March this year, it was just 10.6 million miles (17 million km) away. NASA took the opportunity to study and refine the asteroid’s position, which the space agency did using the radio antenna at Deep Space Network’s Goldstone Deep Space Communications Complex in California. This instrument allowed the team to calculate Apophis’s position to an accuracy of roughly 490 feet (150 meters).
Marina Brozovic, the JPL scientist who led the radar campaign, said if “we had binoculars as powerful as this radar, we would be able to sit in Los Angeles and read a dinner menu at a restaurant in New York,” as she explained in the statement.
Using the Green Bank Telescope in West Virginia, the team was able to double the strength of the incoming radio signal, resulting in an imaging resolution of 127 feet (38.75 meters) per pixel.
Analysis of the data is still incomplete, and the team is hoping to better characterize the shape of Apophis (it’s suspected to have a bilobed appearance, in which two asteroids fused together to create a peanut-like shape), along with improved estimates of its rotation rate and spin state along its axis. These numbers will help to predict the object’s behavior for the 2029 flyby, which scientists say is a once-in-a-thousand-year opportunity to study an object of this size from such close proximity.
With Apophis officially booted from the Sentry Impact Risk Table, the top rated NEOs in terms of risk are the 0.8-mile-wide (1.3-km) asteroid 29075 (1950 DA), which has a 1 in 8,300 risk of hitting Earth in 2880; the 1,608-foot-wide (490-m) asteroid 101955 Bennu (1999 RQ36), which has a 1 in 2,700 chance of impact from 2175 to 2199; and the 121-foot-wide (37-meters) asteroid 2009 JF1, which has a 1 in 3,800 chance of hitting Earth next year (May 6, to be exact, so mark your calendars).
These rankings are based on the Palermo Technical Impact Scale, which takes other variables into account aside from impact probability, such as an object’s potential to inflict wide-scale damage.