urn:nasa:pds:context:instrument:gcms.vl2 1.0 1.16.0.0 Product_Context GCMS 2021-11-16 1.0 First version urn:nasa:pds:context:instrument_host:spacecraft.vl2 instrument_to_instrument_host 10.1029/JS082i028p04641 Biemann, K., J. Oro, P. Toulmin III, L.E. Orgel, A.O. Nier, D.M. Anderson, P.G. Simmonds, D. Flory, A.V. Diaz, D.R. Rushneck, J.E. Biller, and A.L. Lafleur, The search for organic substances and inorganic volatile compounds in the surface of Mars, Journal of Geophysical Research, 82, No. 28, 4641-4658, 1977. Gas Chromatograph Mass Spectrometer (GCMS) Mass Spectrometer The Gas Chromatograph Mass Spectrometer (GCMS) was an instrument carried on board the Viking Lander 2 spacecraft. It performed a molecular analysis experiment by searching for chemical compounds in the upper surface layer of Mars and measuring atmospheric composition near the surface. GCMS had high sensitivity, high structural specificity, and broad applicability to a wide range of compounds. Substances were vaporized from the surface material by a heating process while CO2 (labeled with C-13) swept through. The material was then carried into a Tenax gas-chromatographic column that was swept with hydrogen as a carrier gas. While passing through the column, substances were separated by different degrees of retention. The residual stream moved into the mass spectrometer (after hydrogen was removed by hydrogen-only-permeable palladium), and a mass spectrum (masses from 12 to 200 micron) was obtained every 10 seconds for the 84 minutes of the gas chromatogram. In some cases, the same sample was reheated at a higher temperature and analyzed to detect less volatile materials. For atmospheric measurements, gases were directly introduced into the mass spectrometer, bypassing the gas chromatograph column. This description was provided by the NASA Space Science Data Coordinated Archive (NSSDCA).