coming in as well. But it's all AI voice and so I don't believe much of any of it.

https://en.wikipedia.org/wiki/Comet_SWAN
https://en.wikipedia.org/wiki/Solar_and_Heliospheric_Observatory#Instruments
(just as "ATLAS" is also the name of an instrument)

I guess this is the one you'd read about - reached peak brightness from Earth on 16th Sept:
https://en.wikipedia.org/wiki/C/2025_R2_%28SWAN%29
No idea where "100 time the size" comes from. Size of the nucleus? Of the coma or tail? Something to do with apparent magnitude, ie brightness as seen from Earth, perhaps? 3I/ATLAS won't be visible to the naked eye:
https://en.wikipedia.org/wiki/3I/ATLAS says "300 times fainter than comet C/2025 R2 (SWAN)" on 21st Sept.

Did the Mars info come from the Pole Corter observatory?

Waiting to hear what the professional say, and they don't seem out of the ordinary excited about it.
https://science.nasa.gov/solar-system/comets/3i-atlas/

The comet has -- not unexpectedly -- brightened as it has approached the inner solar system, and is now showing obvious cometary features like a coma and a tail. It is about ready to disappear into sunlight as it passes on the far side of the sun from Earth. It does passes fairly close to Mars in a couple of weeks, and there are plans to observe it with one or more of the spacecraft presently in orbit around that planet. It will be reappearing in our morning sky during November, and may be bright enough to see with larger backyard telescopes then.

Comets are a fairly common phenomenon; on average, at any given time a half-dozen or so may be detectable with larger backyard telescopes, and a few dozen can be detected with large telescopes equipped with sensitive electronic CCD detectors. The past few months have actually been below average in terms of cometary activity, but that is starting to pick back up now. One comet, Comet Lemmon, is in the morning sky and bright enough to see with binoculars (from dark rural sites, anyway); it may briefly become bright enough to see with the unaided eye (faintly, and, again, from dark rural sites) late next month when it comes somewhat close to Earth. Comet SWAN -- one of many comets that have been discovered via the Solar Wind ANisotropies ultraviolet telescope aboard the SOHO spacecraft over the past two decades -- is presently bright enough to see with binoculars from the southern hemisphere, and when it comes somewhat close to Earth next month may still be that bright, and visible from the northern hemisphere as well. Nothing in the slightest bit unusual about any of this.

Glad to see your comment.

Happy to oblige . . . feel free to consider me your "go-to" guy for stuff of this nature . . .

about 3I/Atlas and other similar topics. The AI posters on YouTube and other sites are going nuts over this, and competing to produce the most scary, unlikely things as truth.

Bottom line is this: 3I/Atlas is a comet that is coming into the solar system from outside of the solar system. Very rare. Due to that, we don't know as much about its composition, etc. as we do about local comets. In fact, we know very little, actually, about this one. It's exhibiting some characteristics that differ from normal comets.

But, it's millions or billions of years old. It's not some creation of an advanced society. It's a big-ass rock flying through the sky. It's not goinig to hit Mars or Earth. It's going to fly away again, probably never to be seen again.

Are there others like it? Sure. But none of them are on their way to our solar system right now. We're looking for them, see. Just like we found 3I/Atlas. When they show up we'll spot them and the speculation can begin again.

Don't worry. We're more likely to poison our environment and go extinct that be taken out by some interstellar rock.