NASA’s probes reveal possibilities in our own solar system
Back in the 1970’s, NASA was just sending the first wave of robotic explorers into the outer solar system. Thanks to a fortuitous alignment of the planets, and some amazing astro-navigational feats by the folks at the Jet Propulsion Laboratory, we were treated to our first close-up looks at all the outer planets, except Pluto. (Which came just a few years ago thanks to the New Horizons probe.)
But, a funny thing happened during those voyages…while the planets themselves were amazing and awe-inspiring, it turned out that the really interesting places were the moons of the planets. One of Jupiter’s moons, Io, is a literal hell-scape, covered in sulfur volcanoes. (And the first known example of active volcanoes outside of Earth.)
Other worlds, however, were even more interesting than that, because they seemed to be hiding oceans of liquid water just below their surfaces. In fact, several of these ocean worlds exist as moons in the outer solar system, just waiting for us to return to them.
But why bother with oceans of water that are billions of miles away? Well, here on Earth, wherever there’s liquid water, there’s life. So, in the search for alien life, these are the most likely places we’ll find it. And, compared to worlds around other stars, these are right in our back yard.
Europa
Discovered in January of 1610 by Galileo, Europa is a moon of Jupiter, and one of the most promising candidates for a subsurface ocean and life. The surface of Europa is crisscrossed with cracks of varying colors.
The cracks are in the surface ice of an ocean that covers the entire moon and the colors are caused by…well, we don’t know yet. But one hypothesis is that the material in the cracks is organic material, ejected from below by plumes or a process similar to the plate tectonics we have here on Earth.
Of course, if the surface is covered with ice, how does the ocean below stay liquid? That’s due to tidal forces on the planet caused by Jupiter’s gravity. Just as our moon causes tides that move the oceans here on Earth, Jupiter causes tides in Europa’s waters. Those tides generate heat, and that heat keeps all but the outermost water in a liquid state.
Enceladus
Moving (much) further out into the solar system, we have Enceladus. One of Saturn’s larger moons, Enceladus is home to another (suspected) sub-surface ocean. It definitely has water geysers (which were photographed by the Cassini probe), with more than 100 individual identified geysers. Fun fact:
The geysers of Enceladus are the source of the particles in Saturn’s outermost, “E” ring. The E ring is actually unstable, and, without the geysers of Enceladus replenishing it, would have disappeared long before we would have ever seen it.
The southern region of Enceladus is also covered in cracks similar to Europa. This suggests that, here too, we have an ice shell that breaks, which allows sub-surface water to flow out, where it promptly freezes.
Triton
Much, much further out, around Neptune, we have Triton. Because Triton is so far away from the Sun, it’s a real long shot for a liquid water ocean, but there are some tantalizing hints that one might be there: geysers, surface cracks similar to the ones at Europa and Enceladus, and a surface that’s otherwise “younger” than you’d expect for an object so far out in the Solar System.
And More!
The above is just a sampling of possible ocean worlds that exist in our solar system. There’s also Jupiter’s moon Callisto, and Saturn’s moon Titan. (A probe was already sent to, and landed on Titan, which was awesome. But, Titan’s lakes are made of liquid methane. It’s basically a world full of natural gas!)
And those are just the moons! There’s also a couple dwarf planets that may have subsurface water along with who knows what in the Kuiper belt out past Pluto.
The point is, one day, we’ll go to all of these places, and we’ll dive down into these oceans. And even if it’s just a microbe, or the European equivalent of a shrimp, one of these worlds may well tell us that we aren’t alone in the Universe.
Steven W. Disbrow is the proprietor of “Improv Chattanooga” on the South Side of town. He also creates e-commerce systems and reads comic books when he’s not on stage acting like a fool.