3I/ATLAS: The Strange, Ancient Comet That Entered Our Solar System

Back in July, astronomers spotted something mental flying through space. Called it A11pl3Z at first, which sounds like a password you’d forget instantly. Turns out it’s a solar system strange object from another star system entirely.

Now it’s got the proper name 3I/ATLAS. The “I” stands for interstellar. That’s only the third object we’ve ever spotted coming from outside our solar system. The third one ever. That’s bonkers when you think about it.

It’s Moving Stupid Fast

This thing’s rocketing through at 152,000 mph. That’s about 245,000 kilometres per hour if you prefer metric. Either way, it’s absolutely shifting.

For comparison, that’s way faster than the other two interstellar visitors we’ve spotted. Oumuamua in 2017 and 2I/Borisov in 2019 were both slower. 3I/ATLAS is basically the Usain Bolt of space rocks.

Solar system strange object NASA confirmed it’s a comet, not an asteroid. It took them a bit to figure that out though. Originally they thought it might be an asteroid because it looked like one in early photos.

Then they spotted the coma – that fuzzy cloud of gas and ice around it. Classic comet behaviour. Also saw a short tail forming. That sealed it. Definitely a comet.

The Alien Spaceship Rubbish

Of course, some bloke had to suggest it might be aliens. Harvard astronomer Avi Loeb wrote a whole paper asking, “Is the Interstellar Object 3I/ATLAS Alien Technology?”

Same fella who said ‘Oumuamua back in 2017 might’ve been an alien probe. Nobody believed him then either.

Look, an unknown object in space doesn’t automatically mean aliens. Usually just means we haven’t figured out what it is yet. And we know what this is – it’s a comet made mostly of carbon dioxide ice.

The TikTok conspiracy crowd went mad with it, though. Videos claiming scientists agreed it was an alien spacecraft coming to Earth for a “surprise attack” in November 2025. Absolute nonsense.

An unknown object in space heading towards Earth sounds scary until you realise it’s not actually heading towards Earth at all. The closest it’ll get is 1.6 astronomical units away. That’s about 150 million miles. Nowhere near us.

What Makes It Proper Weird

The mystery object in solar system has some genuinely strange characteristics, though. Not alien weird, just scientifically interesting weird.

It started forming its coma way further out than normal comets. Most comets need to get closer than Jupiter before the sun melts their ice enough to create that fuzzy cloud. 3I/ATLAS did it whilst still outside Jupiter’s orbit.

That suggests it’s made of stuff that melts easier than regular solar system comets. Makes sense if it formed in a different star system with different conditions.

It’s also massive. Early estimates said maybe 10-20 kilometres across. That’d make it the biggest interstellar object we’ve ever spotted. Though it might be smaller if it’s mostly reflective ice.

The carbon dioxide to water ice ratio is mental too. About 8:1, which is way higher than any comet we’ve seen from our own solar system. That tells scientists the star system it came from must’ve had loads more carbon dioxide than ours.

It Passed Mars in October

On October 3, 2025, 3I/ATLAS came within 18 million miles of Mars. That’s the closest it got to any planet during its trip through our solar system.

ESA’s Mars orbiters took photos as it passed. Showed up as “a slightly fuzzy white dot” apparently. Not exactly spectacular but still cool that we could photograph an interstellar visitor from Mars.

The thing made its closest approach to the sun on October 29. That’s called perihelion. It was behind the sun from Earth’s view for a while, which got the conspiracy crowd excited again.

Avi Loeb suggested maybe it was an alien mothership using the sun’s gravity to accelerate or slow down whilst hidden from Earth’s telescopes. “If you want to take a vacation, take it before then,” he said, like the aliens were gonna attack in November.

Spoiler: nothing happened. It’s now leaving the solar system. Just a comet doing comet things.

The Government Shutdown Bollocks

Here’s a properly annoying bit. NASA’s Mars Reconnaissance Orbiter took high-resolution photos of 3I/ATLAS as it passed Mars. Best photos yet, about three times better resolution than Hubble managed.

But because of the 43-day USA government shutdown from late September through early November, NASA couldn’t release the images. They’re just sat there whilst bureaucrats argue about budgets.

Representative Anna Paulina Luna from Florida sent a letter to NASA basically saying, “Come on, release the bloody photos.” NASA said they would once the government reopened.

That happened, but as of mid-November we still haven’t seen them. Proper frustrating when you’re trying to study a once-in-a-lifetime visitor.

It Got Brighter Than Expected

When 3I/ATLAS got close to the sun, it brightened way faster than scientists predicted. That surprised everyone.

Comets normally brighten gradually as the sun heats them up and more ice melts. This one lit up quicker. Could be because it’s moving so fast. Could be its weird composition. Could be something about its structure we don’t understand yet.

Scientists noted it’s “distinctly bluer than the sun,” which means gas is contributing loads to its brightness. That’s consistent with carbon dioxide outgassing, which makes sense given its high CO₂ ice content.

Mysterious Object in Space 2025 Might Be Ancient

One Oxford astronomer reckons 3I/ATLAS could be over 7 billion years old. That’d make it older than our entire solar system by more than 3 billion years.

That’s mental to think about. This thing’s been floating through space since before Earth existed. Before the sun existed. Just drifting between stars for billions of years.

It likely originated around another star, somehow got kicked out and has been adrift through the galaxy ever since. Now it’s passing through our neighbourhood by pure chance.

There could be thousands of these things drifting through our solar system at any time. We simply can’t observe most of them, because they are too small or dark. The Vera C. Rubin Observatory in Chile just came online and might start spotting them regularly.

Can We Visit It?

No. It’s moving too fast and we had basically no notice. You can’t just whip up a space mission in a few months.

ESA’s got a mission called Comet Interceptor planned for the future though. It’s designed to sit in space waiting for an interstellar visitor, then launch quickly to intercept it.

That won’t help with 3I/ATLAS though. By the time Comet Interceptor launches, this thing will be long gone.

The European Space Agency’s JUICE spacecraft observed it with various instruments between November 2 and 25. That’s about as close as we’ll get to a proper space mission visit.

Why It Actually Matters

Strange objects in the solar system are visitors that are brilliant for science. They’re the only physical objects we’ve ever studied that formed in another star system.

Everything else we know about other star systems comes from light – telescopes looking at distant stars and planets. But 3I/ATLAS actually came here. We can study its composition directly.

That tells us about conditions in other star systems. How they form, what they’re made of, and whether the building blocks of life exist out there.

If we found amino acids on one of these things, that’d be massive. Would mean the ingredients for life are common throughout the galaxy.

The Truth About It

3I/ATLAS isn’t aliens. It’s not attacking Earth. It’s just a comet from another star system passing through.

But it’s still fascinating. Moving at 152,000 mph, possibly 7 billion years old, made of weird ratios of carbon dioxide ice, brightening faster than expected. That’s genuinely interesting stuff.

It made perihelion on October 29, 2025. It’s now on its way back out of the solar system! By late November, amateur astronomers using a good telescope might be able to see the comet in the morning sky just before dawn.

If you have an 8-inch telescope or larger, give it a try. You’ll be looking at something that took shape around an entirely different star billions of years ago. How mental is that?

In the end, photographs from the Mars Reconnaissance Orbiter will indeed be released. For years, scientists will continue to pore over the data. We’ll learn loads about what conditions exist in other star systems.

But the conspiracy theories? Those died when November came and went with no alien mothership releasing attack probes. Just another comet being a comet.

Still brilliant though. The third confirmed interstellar visitor ever spotted. Won’t forget seeing this one pass through in a hurry.