Study offers new recipe for oxygen on icy moons

Mar 27, 2006

Some may be surprised to learn that bleach-blondes and the enabler of life elsewhere in our solar system have something in common. And, no, it's not intelligence. It is, in fact, hydrogen peroxide. But how that hydrogen peroxide emerges from ice to become life-sustaining oxygen has been unclear. Now, a new study at the Department of Energy's Pacific Northwest National Laboratory in Richland, Wash., offers the most detailed picture to date on how oxygen can be made in frigid reaches far from Earth.

Since its discovery on Jupiter's Europa and other icy moons orbiting large gaseous worlds, extraterrestrial ice as a source for oxygen has presented the tantalizing possibility of complex life around other planets. Yet planetary scientists have struggled to explain how, in the absence of sufficient heat, oxygen could be produced from the permafrost surfaces for use, in Europa's case, by whatever life forms that might inhabit oceans trapped beneath.

Europa, and detail of its icy surface. (NASA images.)
Europa, and detail of its icy surface. (NASA images.)

The standard explanation is that abundant high-energy particles from space--protons, ultraviolet photons, electrons--break the molecular bonds that chain oxygen to hydrogen. (The geophysics – how the oxygen gets into the ocean as ice is – is another story, one involving a conveyor-belt-like recycling of surface ice into the ocean.)

Those previous oxygen-production models, however, don't jibe with what staff scientist Greg Kimmel and his colleagues at the PNNL-based W.R. Wiley Environmental Molecular Sciences Laboratory have been seeing in experiments, Kimmel reported Monday at the annual meeting of the American Chemical Society.

"The previous model was a two-step process," Kimmel said. "First, an energetic particle produces a stable precursor"--say, two hydrogen atoms coupled with two oxygen atoms (hydrogen peroxide) or a hydrogen atom paired with two oxygen atoms. "In step two, another energetic particle produces O2, or molecular oxygen, from the stable precursor."

Kimmel and colleagues grew a microscopically thin ice film on a platinum surface, under a vacuum, and bombarded the film with high-energy electrons. The bursts lasted 30 to 60 seconds at 30 to 130 degrees Kelvin, approximating the minus-hundreds-of-degrees-Fahrenheit temperatures on the icy moons. Afterward, they measured the amount and location, determined by the oxygen isotopes used to construct layers of the ice film, and discovered that intermediate species of hydrogen-oxygen permeated the films.

"We found that a simpler two-step could not account for our results," Kimmel said. "Our model is a four-step process." First, the energetic particle produces what is known as a common "reactive oxygen species" called a hydroxyl radical, or OH. Next, two OH molecules react to produce hydrogen peroxide. Third, another OH reacts with the hydrogen peroxide to form HO2 (hydrogen coupled to two oxygen atoms), plus a water molecule. And, finally, an energetic particle splits an oxygen molecule from the HO2.

The experiment introduced another new twist. "One might have expected O2 to be produced throughout the region where the electrons penetrate in the film," Kimmel noted. "But this is not the case. It appears that the OH's can be made deeper in the film, but that they subsequently diffuse to and collect at the ice surface with the rest of the reactions (steps 2-4 above) preferentially occurring there."

Source: Pacific Northwest National Laboratory

Explore further: New insights found in black hole collisions

add to favorites email to friend print save as pdf

Related Stories

Seafloor holds 15 million years of monsoon history

Mar 02, 2015

When the research vessel JOIDES Resolution returned to port in late January after a two-month cruise, it had harvested more than 550 sediment cores from deep beneath the Indian Ocean. Locked within those ...

Interesting facts about planet Mars

Feb 16, 2015

Mars is a constant point of discussion for space explorers around the world. We've sent dozens of spacecraft there to study it. Some want to land astronauts on it. The planet is just far away to make that ...

Mining the moon becomes a serious prospect

Feb 02, 2015

With an estimated 1.6 billion tonnes of water ice at its poles and an abundance of rare-earth elements hidden below its surface, the moon is rich ground for mining.

Recommended for you

New insights found in black hole collisions

Mar 27, 2015

New research provides revelations about the most energetic event in the universe—the merging of two spinning, orbiting black holes into a much larger black hole.

X-rays probe LHC for cause of short circuit

Mar 27, 2015

The LHC has now transitioned from powering tests to the machine checkout phase. This phase involves the full-scale tests of all systems in preparation for beam. Early last Saturday morning, during the ramp-down, ...

Swimming algae offer insights into living fluid dynamics

Mar 27, 2015

None of us would be alive if sperm cells didn't know how to swim, or if the cilia in our lungs couldn't prevent fluid buildup. But we know very little about the dynamics of so-called "living fluids," those ...

First glimpse inside a macroscopic quantum state

Mar 27, 2015

In a recent study published in Physical Review Letters, the research group led by ICREA Prof at ICFO Morgan Mitchell has detected, for the first time, entanglement among individual photon pairs in a beam ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.