John Bridges: Mars Science Laboratory Blog
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We have left Garden City and are commencing a week of driving. This also marks 10 km on the odometer, at up to 100 m a day we can travel quite quickly.
This NavCam image shows the general view of the terrain in our route forward to Logan Pass and the waypoints beyond.
The heavy noble gases argon, krypton and xenon are known for their non-reactive nature and on Earth used for many applications where a gas is needed to protect a surface from the reactive species in terrestrial air. Welding under argon atmosphere is one example, and krypton Kr or xenon Xe filled light bulbs for cars is another.
In nature the heavy noble gases are powerful tracers of atmospheric processes, such as loss to space and surface-atmosphere interaction. For instance Kr and Xe have undergone much less loss to space over time than hydrogen or carbon, so the current heavy noble gas abundances can tell us about the original composition of the martian atmosphere, before much of Mars' atmosphere was lost about 4 billion years ago.
Curiosity can measure the heavy noble gases in the current atmosphere with the quadrupole mass spectrometer (QMS in the image) in the SAM experiment. But before measuring the noble gases in the atmosphere, other constituents of the Martian atmosphere – such as the CO2 – need to be removed in order to purify the sample. The SAM instrument uses a series of scrubbers and getters to do this. A 2D schematic of the instrument is here: http://ssed.gsfc.nasa.gov/sam/2d/. SAM recently made heavy noble gas measurements – and the exciting news for our team is that one of us (my co-I Susanne P. Schwenzer from the Open University who is an expert in the field of noble gases) recently visited NASA Goddard, where she worked with Dr. Pamela Conrad (SAM Deputy PI) in her new noble gas laboratory and with the recent data.
This MAHLI image (field of view about 20 cm) shows how water has travelled through the Garden City mudstone rock. It has left trails in veins - probably of gypsum or a similar mineral. The purity of the veins suggest that they formed from the redissolution of an evaporite sedimentary layer, perhaps above the current level of sediments.
Meanwhile the SAM team have published findings (link below) showing the presence of gas (nitric oxide NO) formed from the breakdown of nitrates. This nitrate was present in the Rocknest sand and the John_Klein and Cumberland mudstones. That is important because 'fixed' nitrogen of this type is regarded as one of the essential parts of an habitable environment for microbial life.
We have started moving off from Pahrump, towards our next main Waypoint at Artist's Drive. This remarkable site of large sulfate veins is in front of us at Garden City. Such a large concentration suggests that we may be getting closer to a sedimentary layer of evaporite salts, as we progress through the foothills of Mt. Sharp. The middle parts of Mt Sharp show signs of sulphate enrichment because of their spectral signature in the near infra red parts of the spectrum.
This week is also the Lunar and Planetary Science Conference in Houston (home of the NASA Johnson Space Centre). There will be a lot of discussion about MSL results, I am giving a talk about Hematite Ridge - one of the main MSL targets - and how it might have formed through martian weathering.