Martian Dust Devils Solve Viking Puzzle

Aug. 15, 2006 — The ambitious Viking missions to Mars, dispatched in the 1970s to search for life on the Red Planet, left a few puzzles for researchers to ponder, including a soil experiment that showed unmistakable signs of chemical activity.

Followup studies determined the triggering agent was, disappointingly, not organic matter. The mystery lay dormant for 30 years until recently when a team of scientists found proof of another interloper: Martian dust devils.

Whipped by strong winds, mini-cyclones of swirling dust regularly dance across the face of Mars, generating fields of static electricity as particles rub against each other and cast off positive and negative charges.

Scientists believe the electricity may produce reactive chemicals that build up in the Martian soil, a theory that would explain Viking's puzzling results.

"Our calculations indicate that once these electric fields are produced by dust storms on Mars, they free more electrons from atoms and molecules in the thin Martian atmosphere," said Gregory Delory, a senior fellow at the University of California Berkeley Space Science Laboratory.

"These electrons then collide with and break apart molecules such as water and carbon dioxide, creating new chemical products that continue to react with other constituents in Mars' atmosphere."

Delory and his colleagues then calculated how the broken molecules would recombine into reactive chemicals, such as hydrogen peroxide and ozone.

Over time, hydrogen peroxide would become so abundant that it would fall like snow onto the ground, permeating the soil, the researchers said.

The study, which appears in the current issue of Astrobiology, was based on field and laboratory experiments conducted over the past five years.

"We know that strong electric fields are generated by dust storms on Earth," said William Farrell, with NASA's Goddard Space Flight Center in Greenbelt, Md. "Conditions in the Martian atmosphere should produce strong electric fields during dust storms there as well."

"If true," added Delory, "this very much affects the interpretation of soil measurements made by the Viking landers. The presence of peroxide may explain the quandary we have had with Mars, but there is still a lot we don't understand about the chemistry of the atmosphere and soils of the planet."

An experiment slated for NASA's 2009 Mars Science Laboratory mission has instruments that will be able to check for oxidizing substances in the soil, which could prove the team's theory.