New research suggests that there is plenty of oxygen available in the subsurface ocean of Europa to support oxygen-based metabolic processes for life similar to that on Earth. In fact, there may be enough oxygen to support complex, animal-like organisms with greater oxygen demands than microorganisms.

The global ocean on Jupiter’s moon Europa contains about twice the liquid water of all the Earth’s oceans combined. New research suggests that there may be plenty of oxygen available in that ocean to support life, a hundred times more oxygen than previously estimated.

The chances for life there have been uncertain, because Europa’s ocean lies beneath several miles of ice, which separates it from the production of oxygen at the surface by energetic charged particles (similar to cosmic rays). Without oxygen, life could conceivably exist at hot springs in the ocean floor using exotic metabolic chemistries, based on sulfur or the production of methane. However, it is not certain whether the ocean floor actually would provide the conditions for such life.

Therefore a key question has been whether enough oxygen reaches the ocean to support the oxygen-based metabolic process that is most familiar to us. An answer comes from considering the young age of Europa’s surface. Its geology and the paucity of impact craters suggests that the top of the ice is continually reformed such that the current surface is only about 50 million years old, roughly 1% of the age of the solar system.

Richard Greenberg of the University of Arizona has considered three generic resurfacing processes: gradually laying fresh material on the surface; opening cracks which fill with fresh ice from below; and disrupting patches of surface in place and replacing them with fresh material. Using estimates for the production of oxidizers at the surface, he finds that the delivery rate into the ocean is so fast that the oxygen concentration could exceed that of the Earth’s oceans in only a few million years. Greenberg presented his findings at the 41st meeting of the American Astronomical Society’s Division for Planetary Sciences now under way in Fajardo, Puerto Rico.

Our closest view of Europa was provided by the Galileo spacecraft, which orbited the Jupiter system from 1995 to 2003. Now researchers are developing a new plan to study the moon with even greater detail. The Europa-Jupiter System Mission (EJSM) calls for one spacecraft to orbit Europa and another to orbit Ganymede, another large moon of Jupiter that also may have a liquid ocean locked beneath an icy outer layer.

EJSM would be a joint mission of NASA and the European Space Agency, with ESA in charge of the Ganymede orbiter and NASA directing the Europa orbiter. Working together, the two spacecraft also would be able to conduct limited studies of the large moons Io and Callisto, as well as the planet Jupiter.

Brad Dalton of NASA's Jet Propulsion Laboratory, who is helping draft the EJSM proposal, says some of the instruments the Europa orbiter will carry include a camera, a spectrometer, and a powerful radar system. The radar would enable the spacecraft to peer through Europa's ice and figure out just how thick it is.