The first results of the atmospheric analyses have been published this week in Science Magazine. Let by Chris Webster and the SAM team, largely from NASA AMES and jpl, they have used the Tuneable Laser Spectrometer to measure the different isotopic abundances in the current atmosphere. The TLS works through absorption of energy from the lasers by the different atomic nuclei as atmosphere is let in to the instrument.
This work has shown an enrichment in heavier nuclei e.g. Argon 40 compared to Argon 36. The emrichment in Argon 40 (and Carbon 13) is due to the loss of the lighter isotopes of those elements during the history of the Mars atmosphere. There is a lot of debate about how thick the early Mars atmopshere was but many people think it had bars of pressure (mainly CO2). The atmosphere has been lost through a combination of trapping of CO2 as carbonate in the rocks and soil, impact erosion of the atmosphere, escape of lighter isotopes because of their vibration and attaining near escape velocity due to heating in the atmosphere and also through stripping by the solar wind. The solar wind effects became more important after the magnetic dipole field ended on Mars about 4 billion years ago as the planet’s core cooled.
A thicker atmosphere, lasting a long period of time, would have been able to support the sort of habitable environment that we have discovered at Yellowknife Bay.
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