Ah, good ol’ 3I/ATLAS. How I miss writing about you a few days a week.
You were a fun comet. You were a bit of a freak. You came from beyond our solar system, exhibiting all sorts of weird-o behaviors that baffled scientists. So much so that some believed you were an alien artifact when, in fact, you were just a regular space rock.
Once researchers got a clear view of you as you approached Earth, your mystique faded a bit. But that doesn’t mean you’re still not a bit of a freak.
Weirdo Comet 3I/ATLAS Was ‘Erupting’ After It Flew Near the Sun
3I/ATLAS, only the third confirmed interstellar object ever observed passing through our solar system, might be exiting our solar system. But just as it put on a show on the way in, it is appropriately now putting on a show on the way out.
Observations from NASA’s SPHEREx near-infrared observatory revealed that after its close solar flyby, 3I/ATLAS began violently venting material into space. By December 2025, according to Johns Hopkins astronomer Carey Lisse, the comet was “full-on erupting,” rapidly brightening as water ice transformed from solid to gas in the vacuum of space.
That’s not unusual behavior for a comet heated by the Sun. What makes 3I/ATLAS different is its origin story. This object spent eons drifting between stars, bombarded by cosmic radiation. Scientists believe that radiation likely formed a hardened crust on its surface, chemically altered by its time in interstellar space.
Our sun started melting it, causing 3I/ATLAS to put on a show that both dazzled and befuddled us back here on Earth.
As solar heat penetrated beneath the crust, it warmed ancient ice locked deep inside, triggering a series of gassy chemical bursts of water vapor, carbon-rich compounds, soot, rock dust, and myriad organic molecules, all dating back billions of years.
Researchers now have the rare opportunity to observe pristine interstellar material exposed for the first time since before the solar system was formed. Galactic equivalent of unearthing a time capsule, but instead of finding some mix tapes from 1987, it’s a whole bunch of fascinating space debris.
3I/ATLAS will soon fade from view as it exits the solar system, but not before bowing out with one final display of its classic weird-o behavior.
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