Oxygenating Europa's Ocean

 The only place in the entire universe that we know for certain has life is Earth. We have found tantalizing hints of possible life on Mars, Jupiter’s moon Europa, and Saturn’s moon Enceladus. A new scientific study paints an even more optimistic possibility of life on Europa.

Three essential conditions make life possible on Earth. First, life needs water. On our planet, virtually wherever water exists, so does life. Even in conditions of extreme heat, salinity, or acidity, life finds a way. Scientists have found microbes eking out a living in microscopic cracks in rock as much as three miles deep.

Secondly, life needs a source of energy. For most life on our planet, that energy source is the sun. A few organisms obtain energy from superheated water at volcanic vents on the ocean floor where sunlight never reaches. Lower life forms, like plants or microbes, use that energy to power their own life process. Other creatures feed on those plants and microbes. And, finally, life needs oxygen. Even plants, which generate the oxygen in our atmosphere must “breathe” oxygen in the absence of sunlight.

Europa, a moon of Jupiter, has numerous cracks, seen as reddish, crisscrossing lines, in a thick ice shell covering a 100-mile deep ocean. Credit NASA

Two of the most likely places in our solar system to find life beyond Earth are moons: Europa orbiting Jupiter and Enceladus which, orbits Saturn. Both possess a thick covering of ice, beneath which lie oceans of salt water. Europa’s icy shell may be as much as fifteen miles thick. The ocean that lies beneath contains more water than all of Earth’s oceans. Both are too far from the sun to power life. But both orbit large planets with strong gravitational pull. The gravity of the large planet pulls on the moons, squeezing the interior. This generates heat in the core that moves up into the oceans. Without this heating, both moons would be solid ice. For Europa, oxygen exists on the surface. Getting it through the thick ice shell is the problem.

A new study led by researcher Marc Hesse, of the UT Jackson School of Geosciences, suggests a solution. Europa’s surface is covered with cracks. And the pulling, squeezing action of Jupiter’s gravity can pump surface brine with dissolved oxygen through these cracks to the ocean below. They estimate that 86% of the oxygen on Europa’s surface can reach the ocean through this process, allowing Europa’s ocean to carry as much oxygen as Earth’s oceans. "It provides a solution to what is considered one of the outstanding problems of the habitability of the Europa subsurface ocean," Hesse says.

  

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. On the following day, I post that same column to my blog page.

 This is reprinted with permission from the Oklahoman and www.Oklahoman.com.