[meteorite-list] New Theory Explains Reactivity of Martian Soil

[Sterling K. Webb]

Hi,

    Add an electric field sensor to the next Mars Rover...

http://www.sciencedaily.com/releases/2006/08/060802101454.htm

Scientists Suggest Solution To 30-Year-Old Martian Mystery

    Electricity generated in dust storms on Mars may produce reactive 
chemicals that build up in the Martian soil, according to NASA-funded 
research. The chemicals, like hydrogen peroxide (H2O2), may have caused the 
contradictory results when NASA's Viking landers tested the Martian soil for 
signs of life, according to the researchers.
    Lead authors Gregory Delory, senior fellow at the University of 
California Berkeley Space Sciences Laboratory, and Sushil Atreya, planetary 
science professor at the University of Michigan, Ann Arbor, reported their 
results in a tandem set of papers in the June 2006 issue of the journal 
"Astrobiology".
    Dust particles become electrified in Martian dust storms when they rub 
against each other as they are carried by the winds, transferring positive 
and negative electric charge in the same way you build up static electricity 
if you shuffle across a carpet. "From our field work, we know that strong 
electric fields are generated by dust storms on Earth," said co-author 
William Farrell of NASA's Goddard Space Flight Center, Greenbelt, Md. "Also, 
laboratory experiments and theoretical studies indicate that conditions in 
the Martian atmosphere should produce strong electric fields during dust 
storms there as well."
    Delory's team calculated that electric fields generated by the swirling 
dust are strong enough to break apart carbon dioxide and water molecules in 
the Martian atmosphere. "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. 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," said Delory.
    Atreya's team then identified the various ways the broken molecules 
recombine into reactive chemicals like hydrogen peroxide and ozone (O3), and 
calculated the amounts that might accumulate in the Martian soil over time. 
"Once carbon dioxide and water are broken apart, the resulting products 
interact with the other molecules in the Martian atmosphere to produce large 
quantities of the highly-reactive hydrogen peroxide. In fact hydrogen 
peroxide produced by dust electrification can greatly exceed the rate that 
it is produced by the conventional energy source of ultraviolet radiation 
from the sun, so much so that hydrogen peroxide would snow out of the 
atmosphere and permeate the Martian soil," said Atreya.
    In 1976, the twin Viking landers scooped up Martian soil and added 
nutrients mixed with water to it. If microscopic life were present, the 
nutrients would be used up and waste products would be released. Three 
different experiments involved in this test gave conflicting results. The 
Labeled Release and the Gas Exchange experiments indicated something active 
was in the soil, because the nutrients were broken down. However, the Mass 
Spectrometer experiment did not find any organic matter in the soil.
    In 1977, Viking researchers suggested that the apparent contradiction 
could be explained if a very reactive nonorganic substance that imitated the 
activity of life by breaking down the nutrients was embedded in the soil. 
Hydrogen peroxide and ozone were considered possible candidate reactive 
compounds. While ultraviolet radiation from the sun could produce a certain 
amount of reactive chemicals in the atmosphere, there were no physical 
processes known to explain how large amounts of such reactive material could 
accumulate in the Martian soil. Some researchers at the time considered the 
possibility that dust storms might be electrically active in a way similar 
to terrestrial thunderstorms, and that these storms might be a source of the 
new reactive chemistry.
    This dust storm suggestion remained dormant for close to 30 years. The 
Astrobiology papers now provide detailed analysis to support this theory, 
based on results from field and laboratory studies by the team over the past 
five years. The theory could be tested further by an electric field sensor 
working in tandem with an atmospheric chemistry system on a future Mars 
rover or lander, according to the teams.
    The team includes Delory, Atreya, Farrell, and Nilton Renno & Ah-San 
Wong, (University of Michigan), Steven Cummer (Duke University, Durham, 
N.C.), Davis Sentman (University of Alaska), John Marshall (SETI Inst., 
Mountain View, Calif.), Scot Rafkin (Southwest Research Institute, San 
Antonio, Texas) and David Catling (University of Washington). The research 
was funded by NASA's Mars Fundamental Research Program and NASA Goddard 
internal institutional funds.