Neil deGrasse Tyson Talks Life on Mars | StarTalk

Uh, Larry Wour had a question for me. He was—he was like totally there too. Let's find out.

So, let me ask you this: um, Mars, is there a possibility that there could have been— I don't mean microbial life, but I mean actual intelligent, like human life on Mars at one time?

I gone—gone now. I say yes—gone now—now extinct—now extinct. I mean, could Mars have been inhabitable for a variety of reasons? Maybe the atmosphere is different, it's all broken down, all that kind of stuff. So I think about that often.

And some people think life on Earth may have started at Mars. And yeah, they—you get panspermia, it's called. Meteorites coming over, yeah—yeah—yeah, stowaway microbes.

See, I know a little B stuck in a thing coming across the planets. Starts here, spawns there.

So here's the interesting thing about civilization, um, on Earth: mhm, if all humans left Earth today, you can ask how long would you have to wait before there wasn't a trace of our existence here?

MH: You'd have to wait until the continents subducted, bringing entire cities with them into the lower levels of our— the Earth's crust.

And in those zones, it's so hot everything melts back, and it gets spewed out of a volcano again. What's the time frame, uh, for that?

Millions of years.

Millions of years is not that long.

Okay, so now watch: right, Mars is not as geologically active as Earth.

Now, now, but you have to go way, way far back—millions of years? No, billions.

Billions? Oh, so now you're getting into billions—billions—billions—billions.

So I think it's unlikely on Mars we would—we would see settlements along the riverbanks that are now completely dry.

There would be—if why would you lose a city but still have the dried riverbed that's there? That doesn't— that doesn't play right.

If you're going to— but we were relating it to what's here though.

Yes, what—how else can you do it?

I mean, there an alien city that evaporates when they’re done with it?

I mean, I—[Music]—don't evaporating cities like self-destruct.

That's cool.

It's cool, but not likely—not cool, but not likely—precisely.