on Europa

I’m pretty sure I’ve complained before on this blog about budgets and the disconnect between NASA, the public, and Congress. NASA is largely run by folks who grew up on either Star Trek, the moon landings, or Star Trek: The Next Generation, and wants to do all the crazemazing things a space agency ought to do. Congress wants to create jobs and keep technically skilled jobs wherever they can; this occasionally leads to absurdities like the launch tower NASA has spent $349 million maintaining (and continues to maintain), even though the program it was intended for, Constellation, was cancelled in 2010.

But some times the priorities are aligned. Last week, the Obama administration announced funding (in its version of the 2016 budget) for the Europa Clipper mission. It’s a very big deal, because Europa is one of the most fascinating places in the Solar System. http://www.valuewalk.com/2015/02/white-house-approved-nasas-europa-mission/

Europa, the smallest (and second-closest) Galilean moon of Jupiter, as seen by the Galileo space probe

Europa is the smallest of the major moons of Jupiter (slightly smaller than our moon), and the second closest. Since the Voyager flybys of 1980 (thirty-five years ago, and that feels weird to say) planetary scientists have suspected that underneath its icy cueball surface. What with results from the Galileo space probe and other sources, it’s now fairly clear that under miles of ice is a gigantic ocean of liquid water. Gigantic, because there’s probably more liquid water under Europa than there is on the Earth. We’re talking a DEEP ocean. And on Earth at least, where there’s water, there’s life, so on Europa…

But what powers that? Europa’s neighboring moon, Io, is so close to Jupiter that its tides make it perpetually volcanic. The same squeezing tidal forces, on a slightly smaller scale, mean that Europa may have massive undersea volcanoes. Remember the tube worms that grow at deep-sea vents? That may be Europa’s entire ecosystem.

Jupiter's moon Io as seen by the New Horizons spacecraft on its way to Pluto. The volcano Tvashtar is erupting here.

So Europa’s a pretty big deal. The Europa Clipper (not to be confused with the Europa Report) will be a specialized Jupiter orbiter that tries to probe beneath the ice to see if there’s life.

In recent years, some planetary scientists have put forward the idea that Enceladus, a minor moon of Saturn, is a more deserving target. Enceladus is also an icy cue-ball, and it’s also got an ocean of liquid water under the surface… except that one we’re sure of, because cryovolcanism at the south pole is actually shooting it out into space where Cassini can see it. They do have something of a point: To do the science we’d really like to do at Europa, we’d need to find a way to drill through perhaps 60 kilometers of solid ice, which is currently technologically impossible. To check the oceans of Enceladus, we just… fly a space probe through a plume.

I do see some problems with that, though: From things I’ve seen at meetings (such as the AAS meeting), the liquid ocean of Enceladus probably doesn’t surround the rocky core, and it may not always be in the same place. While it’s possible to imagine life that could survive a few million years of deep freeze, that’s a bit farther from life as I know it than something that could survive in a perpetual European ocean. Also, Europa MAY still have volcanoes of its own. I’m not a planetary scientist, but it still sounds like Europa is a place worth going.

Hopefully, if Congress agrees to keep funding the $2 billion mission, we will.


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