[Lee Billings:] Hey folks, it’s Lee Billings at Scientific American joined by my esteemed colleague...

[Mike Lemonick:] ...Mike Lemonick

[Billings:] And together we’re going to give you a very quick rundown of what’s up in the solar system in 2016.

[Lemonick:] Yeah, so let’s start with Mercury, closest planet to the sun. Astronomers have discovered a colossal canyon, twice as deep as the Grand Canyon. Mercury is gradually shrinking as it cools. And as it shrinks it crumples up, like a grape shrinks into a raisin, and making those little crevices—except this is a really big crevice.

[Billings:] Wild. Now, Venus isn’t shrinking, is it?

[Lemonick:] Venus is not shrinking, but it is showing evidence that it might once have had oceans where life could have existed before the temperature went up to 900 degrees. And life could still be persisting in the clouds, and we could actually go look for it.

[Billings:] Okay. We are going to skip over Earth, I guess; no one cares about Earth in the context of space. But lead us to Mars!

[Lemonick:] The Mars Reconnaissance Observer has discovered an ice sheet 560 feet thick and has as much water as Lake Superior. So if you ever get to Mars to live, you’ll have a place to drink.

[Billings:] Man, that’s kind of seeming like a theme here, with water. Moving out into the solar system, there’s a place, a dwarf planet called Ceres—there’s water there, too, it seems! We’ve found actually what looks to be a cryovolcano—a volcano built from flowing liquid water rather than flowing liquid rock. Pretty crazy, even though there’s probably not an ocean there.

But if we move to Jupiter, one of its moons called Europa, there does seem to be a subsurface ocean there—we’ve known that for a long time. But now it seems, based on new observations with Hubble, there are plumes of water vapor emerging from this subsurface ocean, which is a good prospect for life and for us studying it.

So the real news from Saturn is “the end of” news. Because the Cassini mission that’s been there for more than a decade is prepping for the end, changing its orbit, starting to dive through Saturn’s rings—uh lining up for what’s going to be a spectacular plunge into the atmosphere September 15 of next year, when it will burn up.

[Lemonick:] Yeah they want it to burn up so that it won’t inadvertently crash into one of the moons and contaminate it, because there are a couple of moons—Titan and Enceladus in particular—where there’s also evidence of underground oceans where there could be life. And we don’t want to mess that up.

[Billings:] Yet more oceans in the outer solar system. Which leads us to Uranus and Neptune. We don’t really know much about them, and we won’t for some time because there’s no spacecraft there.

[Lemonick:] On to Pluto

[Billings:] Right, on to Pluto! We visited it last year with New Horizons and we’ve been analyzing the data ever since—and guess what’s there.

[Lemonick:] Could there be an ocean?

[Billings:] Could there be an ocean? Yes there could be! It looks like there’s one deep down beneath a few hundred kilometers of ice, maybe more like slush than water—but gosh, an ocean on Pluto?

[Lemonick:] That’s close enough for me.

[Billings:] But of course there’s stuff farther out. Mike?

[Lemonick:] Well yes. Some people call it Planet X, some people call it Planet Nine. There’s indirect evidence of a gigantic planet, 10 times as massive as Earth. We should know within a couple of years whether it’s actually out there.

[Billings:] Another unnamed planet is Proxima b—that’s the nearest neighboring planet to us outside our solar system. That’s about four light-years away and orbits a star called Proxima Centauri. But what’s interesting about Proxima b is that it may also have an ocean because it’s about the same size as Earth. It’s in an Earth-like orbit where you could have liquid water on its surface.

[Lemonick:] But we have no idea if it does.

[Billings:] No idea. Could be Venus, could be a little shrunken raisin like Mercury for all we know.

So if you had to choose between Venus and Mercury, which one would you want to live on?

[Lemonick:] I would rather live on Mercury, because at least you get sunny days.

[laughter]