Author Topic: Scientists suggest solution to 30-year-old Martian mystery  (Read 2717 times)

Offline jacqmans

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Bill Steigerwald / Nancy Neal-Jones                                                           July 31, 2006

NASA Goddard Space Flight Center, Greenbelt, Md.

301 286 5017 / 0039

Release 06-63

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.

For an image, refer to:

http://www.nasa.gov/centers/goddard/news/topstory/2006/mars_soil_chem.html

-end-


Offline zinfab

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"This dust storm suggestion remained dormant for close to 30 years. "

THIS is the reason we must all support the VSE with all our heart, no matter the method that gets us there.

Offline simonbp

Atmospheric electrostatic discharges (ESDs) can produce some nasty ionisation (if you've ever smelt ozone after an electrical spark, you know what this article is talking about), but the role of UV on Mars surface oxidation shouldn't be understated. CO2 is nearly transparent from 200-400 nm, and the range most damaging to organics is UV-C, 200-280 nm. Thus, pretty much any organic material (read Mars bugs) will rapidly decompose in the first 30 cm or so of regolith. Cosmic and solar radiation (and the secondary particles they produce) also have a big hand in ionising the surface.

And it should be noted that the Viking missions did in fact find organics in one of their experiment - oddly enough, it just happened to have the same chemical composition as the cleaning solution used on the lander before launch... :)

Simon ;)

Offline mlorrey

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I don't think that the problem is as significant as claimed, otherwise the Mars Rovers would experience serious electrical problems every time  a dust devil came by, and suffer from serious oxidation problems. The fact that the Rovers have lasted so far beyond their expected lifetimes demonstrates that conditions on Mars are not so severe as these scientists are trying to claim. This sounds to me like some absurd excuse making by those who are vehemently and unscientifically opposed to the idea of life ever having existed on Mars.
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Offline PlanetStorm

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mlorrey - 1/8/2006  10:49 PM

I don't think that the problem is as significant as claimed, otherwise the Mars Rovers would experience serious electrical problems every time  a dust devil came by, and suffer from serious oxidation problems. The fact that the Rovers have lasted so far beyond their expected lifetimes demonstrates that conditions on Mars are not so severe as these scientists are trying to claim. This sounds to me like some absurd excuse making by those who are vehemently and unscientifically opposed to the idea of life ever having existed on Mars.

The argument isn't that life could never have existed, only that the conditions in the upper levels of the regolith are highly unfavourable to organic material surviving there now. That was indicated first by Viking, and then backed up by evidence of a strongly acidic environment (e.g., no carbonates anywhere to be found) by Spirit and Opportunity. There is no evidence that reservoirs life cannot exist beneath the surface.

Incidentally, something that is often forgotten is that all three of the biology experiments (gas exchange experiment, labelled release experiment, and pyrolitic release experiment) on the Viking landers gave positive results for life being present. However, the negative result for organic material completely undermined the initial positive interpretation of the biology experiments, and these were later explained in terms of chemistry in a highly oxidising environment. The labelled release experiment is still argued over quite heatedly though.

Offline mlorrey

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You still haven't addressed my challenge to the claims of electrostatic ionization of CO2 by dust devils. The degree of charge needed to accomplish this would cause significant electrical disturbances to the mars rovers any time a dust devil came by, or especially, when one brushed dust off of the rover, as has happened. This should cause significant power surges, shorts, and overloads.

Additionally, the amount of disassociated CO2 should also result in serious amounts of carbonic acid levels in the mars dust, which would cause serious etching, particularly on solar panels that dust settles on, and it and the peroxide should cause a lot of other corrosion and other forms of oxidation.

Since absolutely none of these things have been observed by either Mars Rover, this theory is bunk.
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Offline PlanetStorm

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mlorrey - 9/8/2006  5:15 AM

You still haven't addressed my challenge to the claims of electrostatic ionization of CO2 by dust devils. The degree of charge needed to accomplish this would cause significant electrical disturbances to the mars rovers any time a dust devil came by, or especially, when one brushed dust off of the rover, as has happened. This should cause significant power surges, shorts, and overloads.

Additionally, the amount of disassociated CO2 should also result in serious amounts of carbonic acid levels in the mars dust, which would cause serious etching, particularly on solar panels that dust settles on, and it and the peroxide should cause a lot of other corrosion and other forms of oxidation.

Since absolutely none of these things have been observed by either Mars Rover, this theory is bunk.


I haven't addressed your challenge to the dust-devil theory because I don't entirely disagree with it. The electrostatic ionization theory might indeed be wrong. But you are missing my point.

The chemistry observations first made by Viking were so unexpected that they completely invalidated a whole set of assumptions behind the bio experiments also on Viking. The unexpected chemistry essentially caused people to reverse the interpretation of the results obtained by the bio experiments. Had the Martian chemistry been different, the Viking bio experiment results would probably now be regarded as clear evidence of microscopic life existing on Mars today.

The unexpected Martian chemistry found by Viking has still to be explained - it is a long-standing and nighly significant mystery. No simple mechanism appears to account for it, so what is happening now is that people are being forced into more exotic explanations. Exotic explanations obviously have a high probability of being wrong, but that doesn't mean that they are wothless theories.

The people proposing this new theory have not stated that life could never have existed on Mars, and that was what I took issue with in your earlier post. They are just trying to find an explanation for a seriously strange (but virtually uncontested) set of observations. As always with a new theory which cannot be directly tested (at least not yet), it has to be tested against a whole set of existing observations that don't directly address the problem. One piece of indirect evidence is the longevity of the rovers. So, on balance, like you, I think the theory is probably wrong too. But I recognise that it is an imaginative attempt to explain what is a real mystery regarding Martian chemistry, and at the moment any new idea is well worth giving a fair trial.

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