Nature‘s Alexandra Witze summarizes recent research suggesting that plate tectonics are at work in Europa’s icy crust. Among other things, this makes it more likely that the oceans underneath the ice could support life.
If you have got an idea for how to study Europa, then NASA wants to hear from you.
The agency has no official plans for a mission to the Jovian moon, whose icy crust covers a watery ocean in which life could theoretically exist. But spurred by intense congressional interest and several recent discoveries, NASA is seeking ideas for instruments that could fly on a mission to Europa. The possibilities range from a stripped-down probe that would zip past the moon, to a carefully designed Jupiter orbiter that would explore Europa over many years.
The groundswell of enthusiasm is likely to be bolstered by the latest big news, reported on 7 September, that there may be giant plates of ice shuffling around on Europa — much as plates of rock do on Earth (S. A. Kattenhorn and L. M. Prockter Nature Geosci. http://dx.doi.org/10.1038/ngeo2245; 2014). Such active geology suggests that Europa’s icy surface is connected to its buried ocean — creating a possible pathway for salts, minerals and maybe even microbes to get from the ocean to the surface and back again.
Simon Kattenhorn, a geologist previously at the University of Idaho in Moscow, and Louise Prockter, a planetary scientist at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, made the finding after combing through pictures from NASA’s Galileo spacecraft, which orbited Jupiter from 1995 to 2003. Most of its pictures of Europa are fairly blurry, but Kattenhorn and Prockter scrutinized one of the few regions of the moon for which high-resolution images exist.
They treated the images as though they were parts of a giant geological jigsaw puzzle, with ridges and bands and other features that have been split and separated by crustal movements, and tried to trace how the surface of Europa had transformed over time. “When we moved all the pieces back together, there was a big hole in the reconstruction, a sort of blank space,” says Kattenhorn. The missing portion, the scientists concluded, must have been somehow sucked down into the moon’s interior.