Europa's Ocean Has Oxygen, May Support Life

Jupiter's moon Europa is flowing with a buried liquid water ocean that contains much more oxygen than previously thought — enough to possibly support life, scientists say.

There is no solid evidence of life for anywhere besides Earth, but Europa has long been considered a good place to look for biological activity.

Europa's ocean lies beneath several miles of ice, so scientists wondered whether it has much oxygen, which is thought to be created at the surface by interaction with energetic charged particles from the sun. Scientists think oxygen is probably necessary for life's metabolic processes, unless some creatures use exotic chemistry involving sulfur or methane.

The global ocean on Europa contains about twice the liquid water of all the Earth's oceans combined. The new research suggests that there may be a hundred times more oxygen than previously estimated.

To probe how much oxygen might lie in the ocean, Richard Greenberg of the University of Arizona studied Europa's surface, which appears to be only about 50 million years old — roughly 1 percent of the age of the solar system — and continually reforming.

He considered three possible 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 oxygen at the surface, Greenberg found that the delivery rate into the ocean is likely so fast that the oxygen concentration could exceed that of the Earth's oceans in only a few million years.

These concentrations of oxygen could be great enough to support not only microorganisms, but also larger animals that have greater oxygen demands, Greenberg said.

The good news for the question of the origin of life is that there would be a delay of a couple of billion years before the first surface oxygen reached the ocean. Without that delay, the first pre-biotic chemistry and the first primitive organic structures would be disrupted by oxidation, or rusting. Oxidation is a hazard unless organisms have evolved protection from its damaging effects. A similar delay in the production of oxygen on Earth was probably essential for allowing life to get started here.

Greenberg will present his findings Friday at the 41st meeting of the American Astronomical Society's Division for Planetary Sciences in Fajardo, Puerto Rico.