NASA wants you to know 3I/Atlas is just a comet

Over the course of the last few months, I've posted about the comet 3I/Atlas -  3I for the third interstellar object that we know has come through our solar system, and ATLAS (Asteroid Terrestrial-impact Last Alert System) for the telescope network that first spotted it. I've posted especially about how the comet seems to have attracted an unusual number of people who were are all emphasizing that it was too weird to be a plain old comet, so it has to be an interstellar space traveler, possibly even crewed by some sort of living aliens.  I even spent some extra time and space explaining why I thought that didn't make much sense. 

Of course, every telescope on Earth or out in the solar system was evaluated with regard to how good a look it could get at the comet.  In the second post about the comet I had said, "why do I think it's basically just another rock? Because it's acting like a rock. It's on a purely ballistic trajectory."  And it continued to act like a rock.  

And then the government shutdown impacted that to some degree. 3I/Atlas had its closest approach to the sun in late October and stayed on the projected course. While enough people went to work to capture images, not enough people did to make the images public and discuss the results. 

So today, NASA held a press conference to discuss everything that we now know about 3I/ATLAS, and how NASA’s hardware contributed to that knowledge. And to say one more time that the object is a fairly typical comet and not some spaceship doing its best to appear like one. 

3I/ATLAS is an extrasolar comet and the third visitor from another star that we’ve detected. We know the comet part because it looks like one, forming a coma of gas and dust, as well as a tail, as the Sun heats up its materials. That hasn’t stopped the usual suspect (Avi Loeb) from speculating that it might be a spacecraft, as he had for the earlier visitors. NASA doesn’t want to hear it. “This object is a comet,” said Associate Administrator Amit Kshatrya. “It looks and behaves like a comet, and all evidence points to it being a comet.”

In every way that it has been measured, photographed and analyzed, 3I/Atlas has come across as a comet.  If there even is such a thing as a typical comet this one is a bit different, but there's a big difference between a slightly faster dusty rock and a crewed spaceship filled with aliens. 

The HiRISE camera, meant to image Mars’ surface, was repurposed to capture 3I/ATLAS. Credit: NASA/JPL-Caltech/University of Arizona

Hubble has gotten the best view of 3I/ATLAS; its data suggests that the comet is, at most, just a couple of kilometers across. It doesn’t show much variability over time, suggesting that, if it’s rotating, it’s doing so very slowly. It has shown some differences as it warmed up, first producing a jet of material on its side facing the Sun before radiation pressure pushed that behind it to form a tail. There is some indication that, as we saw during the Rosetta mission’s visit to one of our Solar System’s comets, most of the material may be jetting out of distinct “hotspots” on the comet’s surface.

Imaging suggests that a lot of the material coming off is in the form of dust grains. NASA indicated that two missions to asteroids, Lucy and Psyche, were especially helpful here, since they were farther from the Sun than 3I/ATLAS, and so could capture backlit images of the comet’s coma.

NASA’s Tom Statler, the lead scientist for Solar System bodies, said that the amount of material being released by 3I/ATLAS is fairly typical of Solar System comets. But some of the details are a bit unusual. For example, the ratio of carbon dioxide to water being released is higher than we see from local comets. Those normally emit iron and nickel together, but 3I/ATLAS seems to be unusually nickel-rich. So, there are indications that it has a history that differs somewhat from our Solar System’s comets.

It's an interesting article, and there's more detail there than I lifted. I suppose it's inevitable that when something unusual, like the third object in human history recognized as being from outside of our solar system comes through, it's going to attract attention. It's just that when the people saying "it's aliens!" capture all the attention, they take away from what's really happening. They minimize the real event. 

For now, NASA has put up a webpage with a large collection of images of 3I/ATLAS and will update the site as more photos become available. But the scientists on the call today emphasized that it’s still very early going in terms of analysis, and some of these ideas may be refined as they make their way through discussions among scientists and peer review at journals.