In Situ measurement of Kr and Xe in the atmosphere of Mars

Friday, 18 December 2015: 15:25
2007 (Moscone West)
Pamela Gales Conrad1, Charles Malespin1, Heather B. Franz2, Melissa G Trainer3, Robert O Pepin4, Susanne P Schwenzer5, Heidi L Manning6, Sushil K Atreya7, Michael H Wong8, John H Jones9, Tobias C Owen10 and Paul R Mahaffy1, (1)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (2)NASA Goddard Space Flight Center, Center for Research and Exploration in Space Science and Technology, Greenbelt, MD, United States, (3)NASA Goddard SFC, Silver Spring, MD, United States, (4)Univ Minnesota, Minneapolis, MN, United States, (5)Open University, Milton Keynes, MK7, United Kingdom, (6)Concordia College, Moorhead, MN, United States, (7)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (8)University of California Berkeley, Berkeley, CA, United States, (9)NASA Johnson SFC, Houston, TX, United States, (10)Univ Hawaii, Honolulu, HI, United States

The Sample Analysis at Mars (SAM) investigation [1] on NASA’s Mars Science Laboratory mission has measured the six stable isotopes of krypton and the nine stable isotopes of xenon from the surface of Mars. Using semi-static mass spectrometry (MS) to measure the Kr, and static MS experiments (first ever on another planet) to measure the xenon, we have obtained isotopic ratios of these heavy noble gas elements with greatly improved precision over the Viking Measurements.

The Viking landers detected both Kr and Xe [2] with a reported precision of ±20%, insufficient for in situ isotope measurement. Using the Viking observation of high 129Xe relative to Earth or to solar wind, Bogard & Johnson [3] and Swindle et al. [4] recognized that Shergottite meteorites may hold trapped Martian atmosphere, from which Swindle’s team later reported precise noble gas isotope ratios, solidifying the theory that these meteorites were of martian origin.

Our data are in very good agreement with the Swindle et al. [4] analysis, and the isotopic distributions of Kr and Xe in present day Martian atmosphere support the Pepin [5] model of massive hydrodynamic escape of the martian atmosphere early after formation.

References: [1] Mahaffy, Paul R., et al. Space Science Revs 170.1-4 (2012): 401-478. [2] Owen, T., et al. Science 194.4271 (1976): 1293-1295. [3] Bogard, D. D. & Johnson, P. (1983) Science, 221: 651–654. [4] Swindle, T. D., M. W. Caffee, and C. M. Hohenberg. Geochim et Cosmochim Acta 50.6 (1986): 1001-1015. [5] Pepin, Robert O. Icarus 111.2 (1994): 289-304.