It's Time To Go Deep Sea Diving on Europa

Once again, Jupiter’s Moon Europa is dishing out the awesome. We know it’s a wet world with vast saltwater oceans lurking under the moon’s cracked icy crust, and according to NASA’s maxim of “follow the water,” this is enough to make Europa a great target for missions looking for life. But the chances of finding life orbiting Jupiter just got better, or at least more interesting. A new paper is suggesting that hydrogen peroxide is abundant on Europa’s surface.

Life as we know it needs liquid water to come into existence and thrive. But water alone doesn’t produce life. Life needs building blocks, the elements that form the basis of all living things like carbon, nitrogen, phosphorus, and sulfur. Hydrogen peroxide decays to oxygen when mixed into liquid water, so its existence on the surface could be one way the life-forming elements get into the subsurface oceans. But Life also needs some kind of chemical or light energy source to get everything mixing, and a compound like peroxide might be the missing link–it could be the energy requirement. Peroxide as energy is another assumption for extraterrestrial life by extension: the availability of oxidants like peroxide on our own planet was a major part of the rise of complex life. The same could be true of Europa.

The latest result came via the Keck II Telescope on Mauna Kea in Hawaii. Using the telescope’s next-generation optics, astronomers gathered images of Europa in the in the near-infrared range of light over four nights in September 2011. Spectroscopic analysis revealed abundant hydrogen peroxide across the surface on the moon’s leading hemisphere, the side that always leads as Europa orbits around Jupiter.

Preliminary measurements suggest an abundance of peroxide of about 0.12 percent relative to water. To put that into some kind of perspective, that’s about 20 times more diluted than the hydrogen peroxide you can buy at a drug store. And it’s firmly on the moon’s leading hemisphere; the concentration of peroxide drops off to nearly zero on the hemisphere of Europa that faces backward in its orbit. Surface regions where the ice is nearly pure water with very little sulfur contamination were also found to have a high peroxide concentration. The peroxide, it seems, is a product of the intense radiation processing Europa's surface ice endures just by virtue of existing in Jupiter’s intensely strong magnetic field.

Like every discovery on Europa, this one didn’t pop up in a single data set from four days of observation. NASA's Galileo mission was the first to find evidence of hydrogen peroxide on Europa when it explored the Jovian system between 1995 and 2003. But Galileo’s observations were limited, seeing a much smaller area than what astronomers were able to see with the Keck telescope.

The big unknown with this discovery is how the surface material and liquid ice might mix. This is the central question since getting the peroxide into the liquid water is necessary for life.

Happily, we might start answering that question sooner rather than later. This past Tuesday, President Obama signed a continuing resolution that was recently passed by the House and the Senate that outlines how the government will spend its funding for the remainder of the fiscal year. The spending package included an increase in funding for NASA’s planetary science research program and $75 million specifically for a mission to Europa. Seed money doesn’t mean the mission will fly, but it’s a promising first step.

The hydrogen peroxide paper, co-authored by famed Pluto killer Mike Brown, was recently published online in the Astrophysical Journal Letters. It’s certainly not the last we’ll hear of peroxide-induced life in orbit around Jupiter. It’s really time we go deep sea diving on that moon.