Ever since the famous “interstellar invader” comet 3I/ATLAS was discovered in our solar system earlier this year, scientists have been enamored with its existence and the serendipity that brought it here — including experts at NASA. As such, the agency has been working to point several of its spaceborne instruments at the peculiar subject, which, incredibly, is only the third interstellar object on record to enter our corner of the cosmos.
Indeed, on Wednesday (Nov. 19), NASA released brand-new images of comet 3I/ATLAS collected by quite a few spacecraft — including the James Webb Space Telescope, the Mars Reconnaissance Orbiter, the Perseverance Mars rover and the Lucy asteroid-studying probe, to name a few. In total, an impressive 15 different agency space missions are confirmed to have their eyes peeled for new data about the interstellar visitor.
The new images, which we’ll discuss below, add to a growing set of footage we have of the object. For instance, we already have some striking stills, such as this composite showing it blasting a jet toward the sun, and this image capturing its growing tail.
And, first and foremost, NASA officials confirmed that comet 3I/ATLAS is actually a comet. In other words, no, it is not an alien spaceship, as many rumors across the internet suggest.
“It looks and behaves like a comet, and all evidence points to it being a comet. But this one came from outside the solar system, which makes it fascinating, exciting and scientifically very important,” NASA Associate Administrator Amit Kshatriya said during the press briefing.
“You kind of know the signatures that you’re looking for; we were quick to be able to say, ‘Yep, it definitely behaves like a comet,'” Fox said. “We certainly haven’t seen any technosignatures or anything from it that would lead us to believe it was anything other than a comet.”
But comet 3I/ATLAS doesn’t need to be an alien spaceship to be unique — it’s still an ancient alien comet.
“It’s a rare opportunity to compare ancient dust from a distant solar system to that from our own,” Shawn Domagal-Goldman, acting director of NASA’s Astrophysics Division, said during the briefing.
New interstellar data
The first image NASA officials highlighted during the briefing was one taken by the closest spacecraft the agency had to the comet: the Mars Reconnaissance Orbiter (MRO). MRO used its HiRISE camera to capture comet 3I/ATLAS on Oct. 2 while the object was about 19 million miles (31 million kilometers) away.
“You can see the comet 3I/ATLAS looks like a fuzzy white ball,” Kshatriya said. “That ball is a cloud of dust and ice called the coma, which is shed by the comet as it continues its trajectory towards the sun.”
Next up, analyzing the view from the current fan favorite and big dog space observatory, the James Webb Space Telescope (JWST), combined with data from the SPHEREx space telescope, has revealed more information than visual imagery of comet 3I/ATLAS could hope to impart. This is because the specialty of JWST and SPHEREx is scanning the cosmos in infrared light, which is invisible to the human eye but rich in things like compositional and thermal data. “We detected an abundance of carbon dioxide gas in the comet’s coma and in the bright cloud of gas and dust surrounding that comet as it approaches the sun,” Domagal-Goldman said.
The infrared data also revealed the presence of water ice alongside carbon dioxide in the comet’s nucleus.
“It does the same thing comets do — it evaporates carbon dioxide gas; it evaporates water,” Tom Statler, NASA lead scientist for solar system small bodies, said during the briefing. “But it’s evaporating more carbon dioxide compared to water — so that’s a very interesting thing.”
One thing is for certain: It’s pretty good that we have so much imagery of comet 3I/ATLAS because of the immense rarity of its passing through our solar system. Understanding the dynamics and composition of such distant cosmic objects can help us decode what the environments are like around other stars. What materials are present? What conditions might give rise to comets like 3I/ATLAS? Already, we’re finding 3I/ATLAS to be rather special.
“It’s going to look different because it didn’t come from our solar system, and that’s what makes it so magical,” Fox said.
And, on the note of the JWST, this instrument will probably be the last of our spacecraft fleet to lay eyes on comet 3I/ATLAS as the object leaves our vicinity. This is because JWST is built to look deeper into the universe than ever before, so it should be able to pick up a signal even after other probes lose the target.
Comet 3I/ATLAS has also previously exhibited a few surprises compositionally in this vein, such as with its strikingly rapid brightening during its closest approach to the sun on Oct. 29. There also appeared to be a glowing nickel vapor in the gas surrounding 3I/ATLAS while the comet was considerably farther from the sun. This was weird because, at that distance from our star, “vapor” isn’t likely to be spewing off an object. It’s thought to be far too cold there for this to happen.
Statler said during the briefing that, though we know comets emit nickel and iron, 3I/ATLAS is putting out more nickel than iron, for some reason: “That’s really interesting, really remarkable, and something to be studied in the future.”
During the briefing, it became clear why it’s important to have so many different spacecraft capture images and data about comet 3I/ATLAS. Not only is it beneficial to combine different instruments’ data, as we saw with SPHEREx and the JWST, but it’s really all about the angles when imaging something as dynamic as an object shooting through the vastness of space.
“Comet 3I/ATLAS has come through on a trajectory in the opposite direction and has arrived at its closest point to the sun when the Earth was on the wrong side for us to conveniently observe,” Statler said. “But Mars was on the correct side of the sun, and our Mars assets were able to observe the comet, and also several of our other spacecraft were on the correct side of the sun.”
Spacecraft tag-team
NASA’s Psyche asteroid mission, which is currently headed toward the metal-rich space rock 16 Psyche, acquired four broadband images of the comet over the course of eight hours on Sept. 8 and Sept. 9 while the comet was about 33 million miles (53 million km) from the spacecraft.
The following week, the Lucy spacecraft on its way to study the Trojan asteroids of Jupiter observed the comet from the opposite direction, while about 40 million miles (64 million km) away. It caught the comet’s coma, halo of gas and even its tail.
“You do not get these views unless you have spacecraft farther from the sun than the comet is so that you can see it backlit. We could not get this view from the vantage point of the Earth,” Statler said.
Mars spacecraft also got an opportunity to view comet 3I/ATLAS as the object passed within 20 million miles (32 million km) of the Red Planet at the beginning of October. That’s when MRO viewed it, and it appears that NASA’s MAVEN (Mars Atmosphere and Volatile Evolution) orbiter did as well.
And it doesn’t end there. The European Space Agency (ESA) and NASA have a project called the Solar and Heliospheric Observatory (SOHO), which imaged 3I/ATLAS from Oct. 15 to Oct. 16 after it had passed Mars from about 222 million miles (357 million km) away, and NASA’s Parker Solar Probe got a glimpse as well — a glimpse scientists can’t wait to parse out.
“NASA assets that are gathering observations of 3I/ATLAS include Hubble, the James Webb Space Telescope, TESS, Swift, SPHEREx, Perseverance Mars rover, Mars Reconnaissance Orbiter, Maven, Europa Clipper, Lucy, Psyche, my personal favorite Parker Solar Probe, PUNCH, STEREO and NASA’s SOHO mission,” Fox said to sum it up.
“The answers will come later on. We are still at this phase, very much in the state where we’re figuring out what are even the right questions to ask about interstellar objects,” Statler said.
For instance, scientists are still zeroing in on the comet’s previous and predicted path. In fact, Europe’s ExoMars Trace Gas Orbiter spacecraft orbiting the Red Planet observed 3I/ATLAS between Oct. 1 and Oct. 7. That’s when the comet passed pretty close to Mars. Thanks to this, scientists managed to glean a highly accurate prediction of the comet’s trajectory, and they say this knowledge could help bolster our planetary defense skills so we can refine strategies to protect Earth someday from a space object headed our way.
There’s still a lot more to be learned about comet 3I/ATLAS — for example, scientists can’t even confirm yet what its size is. The range right now is between a couple of thousand feet to a couple of miles in diameter, and the fact it’s so obscured by dust makes it difficult to resolve the object’s shape. The most interesting thing, though, perhaps concerns its birthplace.
“It would be fabulous if we could trace back the incoming trajectory into the solar system and trace that back and figure out where it came from,” Statler said. “But things are not quite so simple.”
As Stalter explained, the sun and all the other stars in our galaxy are in orbit around the center of the galaxy, meaning we can assume 3I/ATLAS has been in interstellar space for a very long time.
“We can’t say this for sure, but the likelihood is it came from a solar system older than our own solar system itself, which gives me goosebumps to think about,” he said.
