NASA’s advisory group for exploration of the outer planets (Jupiter and beyond) met last week in Laurel, Maryland, where they spent a fair amount of time discussing the habitability of Europa, an icy moon with a subsurface ocean underneath, and what missions could be launched to this intriguing natural satellite of Jupiter in the near future.
The exciting news is that NASA’s program scientist for the outer planets, Curt Niebur, said the agency is considering adding life detection instrumentation as part of the payload of its planned mission to Europa in the 2020s. This would go much further than simply trying to assess Europa’s potential habitability by investigating how thick the ice shell is, the depth and saltiness of the ocean underneath, and the nature of any non-water component in Europa’s icy crust.
Europa has been a top astrobiological target for a while, but the discovery of water plumes on the ice moon ratcheted up the scientific interest even more. If water spouting up from the ice-covered ocean contains living cells, it would conceivably be much easier to detect life in that plume than by melting our way down through tens of meters or possibly even kilometers of water ice.
It would still be challenging, however. The radiation environment at Europa is extremely detrimental to the survival of any organic compounds, including life. But perhaps the plumes can be investigated, for example, with a modified version of Bob Pappalardo’s Europa Clipper concept, if the orbiting spacecraft could catch recently ejected material from the plume and analyze it right away. Alternatively, ice from Europa’s surface could be melted and analyzed in situ by a lander without reaching the ocean underneath. A lander is also being considered as an option for the Europa mission, and water ice is well suited to preserve life. However, one would have to get to the ice that lies more than a meter deep, because the upper meter is strongly altered by Jupiter’s radiation output.
Details of the planned mission to Europa are still being decided, but the possibility of a lander, and now the inclusion of life detection instrumentation—if the experiment can be done in a convincing way, and with a weight of about 110 pounds or less—does exist. If it does fly, we would have, after 40 years, a second mission (Viking was the first) with life detection on another planetary body as a major goal.