The Occasional Journal
Entry No. 8 - 26th September 2004
The "Abstract" Battle for Life on Mars
The Mars Methane Controversy. The last entry to this journal ended with comments made by Professor Formisano of the European Space Agency (ESA) to Linda Moulton-Howe.
"Speculation is that already methane is a rather strong indicator life is probably present today on Mars. Just simply based on methane. ...Formaldehyde is destroyed in the Martian atmosphere within 7.5 hours. There is no way that formaldehyde can exist and remain for a long time in the Martian atmosphere. If (formaldehyde) confirmed, possibly life on Mars today, yes." - Vittorio Formisano, Ph.D., Physicist Principal Investigator of the Planetary Fourier Spectrometer for Mars Express.
Methane on Mars has been confirmed simultaneously by three teams: the ESA Mars Express spectrometer team led by Formisano, a team led by Michael Mumma connected to NASA's Mars Odyssey probe, and a team of astronomers led by Vladimir Krasnopolsky using an Earth based telescope.
The first off the block to have a paper published suggesting that the methane is likely to be a waste product from Martian life has been Krasnopolsky's team. The abstract for this paper, which was published in Icarus in August 2004, is reproduced below. (Further details can be found by clicking this "stargate" µµµ.)
"Using the Fourier Transform Spectrometer at the CanadaFranceHawaii Telescope, we observed a spectrum of Mars at the P-branch of the strongest CH4 band at 3.3 µm with resolving power of 180,000 for the apodized spectrum. Summing up the spectral intervals at the expected positions of the 15 strongest Doppler-shifted martian lines, we detected the absorption by martian methane at a 3.7 sigma level which is exactly centred in the summed spectrum. The observed CH4 mixing ratio is 103 ppb. Total photochemical loss of CH4 in the martian atmosphere is equal to 2.2 x 105cm -2s-1, the CH4 lifetime is 340 years and methane should be uniformly mixed in the atmosphere. Heterogeneous loss of atmospheric methane is probably negligible, while the sink of CH4 during its diffusion through the regolith may be significant. There are no processes of CH4 formation in the atmosphere, so the photochemical loss must therefore be balanced by abiogenic and biogenic sources. Outgassing from Mars is weak, the latest volcanism is at least 10 million years old, and thermal emission imaging from the Mars Odyssey orbiter does not reveal any hot spots on Mars. Hydrothermal systems can hardly be warmer than the room temperature at which production of methane is very low in terrestrial waters. Therefore a significant production of hydrothermal and magmatic methane is not very likely on Mars. The calculated average production of CH4 by cometary impacts is 2% of the methane loss. Production of methane by meteorites and interplanetary dust does not exceed 4% of the methane loss. Methane cannot originate from an extinct biosphere, as in the case of "natural gas" on Earth, given the exceedingly low limits on organic matter set by the Viking landers and the dry recent history which has been extremely hostile to the macroscopic life needed to generate the gas. Therefore, methanogenesis by living subterranean organisms is a plausible explanation for this discovery. Our estimates of the biomass and its production using the measured CH4 abundance show that the martian biota may be extremely scarce and Mars may be generally sterile except for some oases."
On Earth such methane belching bacteria are found in the guts of animals, at the bottom of swamps or deep underground and are known as methanogens. They require no oxygen. Underground colonies get by on water, hydrogen in rocks and carbon dioxide, (see µµµ). The interesting thing is that there is another group of Earth bacteria that feed on methane. These methanothrophic/methanotropic bacteria can live in environments both with and without oxygen. They get by on any source of water, methane and formaldehyde - the latter of which usually kills bacteria (see µµµ). Crucially, formaldehyde tends to form easily in the presence of any methane source.
There is therefore scope for there to be a symbiotic ecosystem of methanogenic and methanothrophic bacteria under the Martian surface. The methanogens produce the methane and formaldehyde that the methanothrops require. The methanothrops mop up the methane and formaldehyde that would otherwise poison the methanogens. The efficiency of such a system may be such that very little of the methane produced by the methanogens leaves the ground. There may therefore be much more than a few "oases" of bacterial life on Mars as suggested by Krasnopolsky.
It is just such a living methane cycle ecosystem that is being advocated by Formisano's paper on discoveries from the Mars Express space probe. The abstract for this paper was released at the International Mars Conference in Italy in September 2004, (see µµµ). The concluding sentence of this abstract is as remarkable as that of Krasnopolsky's.
"A symbiosis of methanogenic bacteria with methanothrophic bacteria in the Martian underground can be an alternative interpretation and looks more likely."
Currently Formisano is in brain-to-brain combat with the editors and external referees of Nature to have his paper published there. The strict embargo policy of this publication means that he isn't allowed to speak publicly about why he thinks a living methane ecosystem is the most "probable" explanation for the renewal of methane and formaldehyde in the Martian atmosphere. Presumably he uses similar arguments against other sources as those in the Krasnopolsky paper that was peer reviewed by Science and published in Icarus.
Formisano has said that he is unhappy with the way his abstract was set out, but there is no doubt from comments that he has made that he wants his paper to put the case for life on Mars. The peer review process in Nature is particularly tough and Formisano is known to be having an uphill struggle to have Nature publish his paper. Generally, the referees are revisiting the case for the other non-living methane sources such as the action of geothermal water on minerals, fossil methane from a long extinct biosphere, and comets. (The latter would involve a comet colliding with Mars within the last few hundred years - or much less if the cometary methane was being chemically mopped up by the Martian soil. However, the odds are against us being in a short post collision window before the hypothetical cometary methane disappears). These issues are covered in more detail in the following links.
µµµ Click "stargate" for latest interview of Professor Formisano by Linda Moulton-Howe
µµµ Oliver Morton's blog pages on the International Mars Conference.
µµµ NASA's Michael Mumma interviewed by Linda Moulton-Howe
The Ammonia Controversy - The curious case of the dog that won't bark. The strangest development to come out of the search for bio-marker gases in the Martian atmosphere is the possibility that the Mars Express has found ammonia there. The BBC's chief science correspondent (David Whitehouse) recently ran a story citing an off-the-record NASA source that ESA had discovered ammonia on Mars, (see µµµ). ESA's press office angrily repudiated this, calling it a "hoax".
Then in true "Mars in Wonderland" fashion the ESA website published a spectral chart from the Mars Express that apparently indicates the recording of ammonia (NH3), which is still on the internet at the time of writing. (See Enterprise Mission screen capture µµµ). Ammonia is another bio-marker intimately associated with life, being a product of the breakdown of the amino acids in proteins. Like methane and formaldehyde, it too must be constantly replenished to exist in the Martian atmosphere. It can be belched from volcanoes, but the infra-red camera on the Mars Odyssey has found no evidence of current vulcanism on the planet.
Despite this Professor Formisano himself has denied that Mars Express has discovered ammonia on Mars saying that the spectral chart (linked previously) merely indicates where ammonia would be if it were to be confirmed. The ESA web page mentioning ammonia has been updated since the Enterprise Missions screen capture (see µµµ) to include several spectral charts in a sideways scrolling Macromedia display. By scrolling this chart to the right we not only find the original chart captured by the Enterprise Mission, but also a part of the spectra that is marked "unknown (ammonia?)". This suggests that Formisano's team had yet to rigorously confirm the existence of ammonia, but had their suspicions.
If they do confirm (or have already confirmed) ammonia readings then this will be their secret weapon in the race to be the first to accurately model Mars as having a biologically modulated atmosphere.
That would be quite a shift from the cold, dry, dead Mars model that has been the respectable scientific convention since the Mariner spacecraft flew by Mars in the late 1960's and early 1970's.
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