2001MarsOdysseyGRSRDS1HENDWorkshop2002.pptVIP

Mars Odyssey Gamma-Ray Spectrometer Mars Odyssey GRS Timeline 2001 April 07 – Launch 2001 June – 7 day warm anneal (~42° C) 2001 June 27 – Begin cruise data collection 2001 August 30 – End cruise data collection 2001 October 23 – Mars orbit insertion 2002 February 09 – Begin mapping phase 2002 March – 10 day warm anneal (~52° C) 2002 March 26 – Resume mapping 2002 May – 10 day hot anneal (~73° C) 2002 May 21 – Resume mapping 2002 June 04 – Boom deployment Gamma-Ray Spectrometer Ge vs. NaI GRS Accumulation Times GRS Coverage Cruise Spectrum Background Lines Solar Proton Events During MO Cruise Detector Configuration Line Shape and Trapping Radiation Damage and Detector Annealing Comparison of Cruise to Mars Orbit Orbital Spectrum – High Energy Orbital Spectrum – Low Energy Why do we believe it’s H20? Hydrogen can combine with many elements, such as sulfur to form H2S, or metals to form hydrides, but these compounds are not likely to be stable given the highly oxidizing conditions on Mars. Many theoretical studies have predicted the regions where water ice should be thermodynamically stable on Mars. Farmer and Doms (1979) conclude that ground ice should be stable in the regolith where temperatures never exceed 200 K. ~10 cm depth at 80° latitude ~100 cm depth at 50° latitude Mellon and Jakosky (1993) model water ice stability at various depths below the surface versus latitude. Summary The Mars Odyssey gamma-ray and neutron spectrometers have identified a significant water ice component south of -60° latitude. The ice is not uniformly distributed within the soil but is buried under an ice-poor layer. North of 60° latitude there is a thick seasonal CO2 cap that is opaque to gamma rays. We are detecting many gamma-ray lines from elements on the surface of Mars, in addition to H, that are of geochemical significance: Th, U, K, O, Si, Mg, Cl, Fe … Over the life of the mission (2 years) many of these elements will be mapped with a spatial resolution of order a few hu