NASA's Europa Clipper

NASA's Europa Clipper launched yesterday on a SpaceX Falcon Heavy rocket; it is due to arrive at Jupiter in 2030.

The point is to search for signs of life at Jupiter's moon Europa. Europa has an icy crust that is regularly remade and smoothed over, which means there is a big ocean of water underneath it. Electromagnetic studies show that the ocean is salty. There is also plenty of energy, in the form of tidal stresses and Jupiter's intense electromagnetic environment. So, a plausible place to look for life.

On the down side, those same electromagnetic fields would rapidly tear apart many of our key molecules, such as DNA and RNA. So Europan life would have to be quite different from ours. Which is, to me, part of the appeal: I tend to think that the first time we find alien life it will be so strange to us that we will have trouble deciding if it is alive or not.

The Europa Clipper won't drill down to that buried ocean. Instead it will repeatedly fly by the moon's surface, scanning it with a variety of instruments and scooping molecules out of its extremely thin atmosphere to study. We know that Saturn's moon Enceladus sometimes erupts with great jets of water from its subsurface ocean, and while we aren't certain that happens at Europa there is some evidence for it, and NASA is hoping to observe such a plume and fly the Clipper through it.

I am not optimistic that life will be found, but I think the search is worth trying; certainly the chance is higher than on Mars. And even if we don't find life, perhaps we will learn more about these strange worlds and their vast, dark oceans.