John Bridges: Mars Science Laboratory Blog
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I am at the American Geophysical Union Conference in San Francisco. The big MSL news here is the publication of our discovery of methane in the martian atmosphere. This was done with the Tunable Laser Spectrometer in SAM. Samples of the atmosphere were let in to the spectrometer over a 20 month period. This spectrometer uses infrared lasers and mirrors to measure the absorption of light by atmospheric gases. From this methane CH4 is identified, even in very small quantities. Totals reached about 7 parts per billion atmospheric molecules, which is hundred of times less than the Earth's atmosphere. However it raises one of the big questions of Mars exploration - if there is methane, is that a sign of past life?
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My contribution with colleague Dr Susanne Schwenzer, to the methane work published in Science this week, is to check the composition of the rocks we drove over at the time of each methane analysis to see if there is any link to the methane releases. There isnt so we have an unidentified source.
Methane can form in a variety of ways - one of them is the alteration of the mineral olivine. I am talking about the alteration of the Gale rocks in one of the other AGU sessions. Its part of a paper that we have just got 'in press' at the Journal of Geophysical Research - the first UK-led paper on Mars Science Laboratory. We show that a mixture of olivine and amorphous/glassy material altered as the sediments were buried and heated in a wet environment to form clay and magnetite - two of the minerals identified by CheMin. This is helping to piece together how water interacted with the martian crust.
At Pahrump we are considering potential drill sites. The heavy signs of veining and water will make for an interesting mineralogical and fluid composition study.
Meanwhile as a benchmark in the mission's progress there has been a public announcement about the Mt Sharp results, which includes the sediments we have been studying as we have drive around in Pahrump. From the early sols of the misioin e.g. Hottah, Link localities we knew we had fluvial river depsits but the flat lying sediments and cross bedding suggest that Gale has also preserved lake deposts.
Looking at the classic Mars Global Surveyor wide angle view of Mars and its atmosphere you can see the heaviliy cratered surface of Mars. Many craters have sediment mountains and signs of rivers. So there were probably widespread lakes at this time on Mars' ~3.7 billion years ago. An ocean on Mars used to seem implausible, but our ideas about Mars are now evolving so rapidly that such theories will be revisited.
This NavCam image shows a dusty view of Mt Sharp and its layers. It is a sign that we are very close to summer solstice again. That occurs at a Solar Longitude (Ls) of 250 degrees, where Ls = 0 is the Spring Equinox in the northern hemisphere. During southern summer on Mars, the south polar cap is relatively warm and so its CO2 is released into the atmosphere, with the thicker atmosphere able to carry more dust.
Not a good time for imaging the far distance.
We are continuing our detailed traverse around the Pahrump area. I will be Geo ScienceTheme Lead tomorrow and we aim to do more contact science. The MastCam image is of Book Cliffs. You can see the Dust Removal Tool area where we now have APXS compositional data. The ridges in this sediment are clear signs of the passage of water from through cracks after the sediment was buried. One of the significant points about this for understanding the history of water in Gale Crater is that there must have been a large amount of water passing through the sediment over a protracted period of time to create a relatively large mass of secondary minerals.