The Europa Ocean Discovery mission

Ever since the first proposal that tidal heating of Europa by Jupiter might lead to liquid water oceans below Europa's ice cover^1,2,3,4, scientists have speculated over the exobiological implications of such an ocean. Liquid water is thought to be an essential ingredient for life, so the existence of a second water ocean in the Solar System would be of paramount importance in any search for life beyond Earth. We present here a Discovery-class mission concept (Europa Ocean Discovery) to determine the existence of a liquid water ocean on Europa and to characterize Europa's surface structure. The technical goal of the Europa Ocean Discovery mission is to study Europa with an orbiting spacecraft. This goal is challenging but entirely feasible within the Discovery envelope. There are four key challenges: entering Europan orbit, generating power, surviving long enough in the radiation environment to return valuable science, and completing the mission within the Discovery program's constraints on launch vehicle (Delta II or smaller) and budget (∼$250M plus launch). Europa Ocean Discovery will carry four scientific instruments to study Europa: (1) An ice-penetrating radar sounder to probe tens of kilometers below Europa's surface; (2) A laser altimeter, to determine the height and phase of Europa's time-varying tidal bulge; (3) An X-band transponder to determine Europa's gravity field; and (4) A solid-state optical imager. These instruments will provide important information about Europa's surface, subsurface, and will provide definitive evidence about the existence of a Europan ocean.