High resolution sampling of the Martian atmosphere

While the attention of the world has been focussed for the last few months on the Curiosity rover that landed on Mars in 2012, another Martian probe has been quietly going about its business for the last five years or so. The Mars Reconnaissance Orbiter was sent to Mars to try and shed more light on the variations in climate and weather that occur in the long-term. As part of this project, it has been using its Compact Reconnaissance Imaging Spectrometer for Mars, known as CRIMS, to measure the atmospheric abundances of carbon monoxide, carbon dioxide and water over 3 Martian years (5 Earth years). CRIMS is a hyperspectral imager operating at high resolution in the UV and near-IR region (362 to 3920 nm).

Now, scientists from NASA/GSFC and the Johns Hopkins University have published details of how they constructed a look-up table to accelerate and faciliate interpretation of the data. It is not a conventional 2D table, but an N-dimensional grid which holds parameters corresponding to the orientation of the spacecraft and the Sun when measurements were taken, various temperature measurements (air, surface and near-surface) and the H₂O column vapour, the CO₂ surface pressure and the CO mixing ratio. With this table, the strength of the gas absorption can be related to the gas abundance.

The team found that CO₂ abundances closely followed the topography, CO has a constant mixing ratio, and the H₂O abundance varied with topography and surface pressure. The data include many CRIMS measurements that were taken at Gale Crater which were used during its evaluation as a landing site for Curiosity.

Image: courtesy NASA