Discovery of 200-km-high (124-mi.) ice geysers above the southern hemisphere of Europa has raised hopes that a flyby mission already in the works may raise the near-term chances of finding life in the global ocean beneath the frozen surface of Jupiter's big moon.
Scientists have long believed that Europa's ocean is one of the few places in the Solar System where life might have evolved, but mission-concept studies to date have focused on penetrating kilometers of ice to find out. Discovery of the geysers by astronomers using the Hubble Space Telescope offers another option.
“If we can actually fly at 10 kilometers above Europa through a plume, we're sampling the subsurface oceans, and if we bring something like the organic analyzers that are built by the mass spectrometry group that built the sample analysis at Mars, and detect organic molecules, that would be pretty phenomenal,” says John Grunsfeld, an astronomer, NASA associate administrator for science and three-time Hubble-servicing astronaut.
Europa has long had a congressional champion in Rep. John Culbertson (R-Texas), who uses his seat on the House Appropriations Committee to funnel funds—$80 million this year and a like amount the year before—for advance work on a “Europa Clipper” mission to the icy moon. With the geyser's discovery, Jim Green, the Planetary Science Division director at NASA headquarters, has ordered additional studies at the Jet Propulsion Laboratory to determine just what instruments might be added to Europa Clipper to take advantage of them.
“Immediately, I asked them to re-look at the payload to determine that they can take advantage of the plumes,” Green says. “They've already seen from the orbit trajectory that they can fly through the plumes, that it is indeed possible and would be planned, and therefore we want to make sure we have the right instrumentation.”
Scientists also want to make sure they actually have seen water. The original observation, announced in a paper published by Science on Dec. 12, 2013, detected very faint ultraviolet emissions of hydrogen and oxygen above the moon's south pole (see illustration) that scientists interpreted as water plumes erupting through cracks in the ice (AW&ST Jan. 13, p. 44).
“We pushed Hubble to its limits to see this very faint emission,” says Joachim Saur of the University of Cologne, one of the Science article coauthors. “These could be stealth plumes, because they might be tenuous and difficult to observe in the visible light.”