In Situ measurement of Kr and Xe in the atmosphere of Mars
The Sample Analysis at Mars (SAM) investigation  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  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  and Swindle et al.  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.  analysis, and the isotopic distributions of Kr and Xe in present day Martian atmosphere support the Pepin  model of massive hydrodynamic escape of the martian atmosphere early after formation.
References:  Mahaffy, Paul R., et al. Space Science Revs 170.1-4 (2012): 401-478.  Owen, T., et al. Science 194.4271 (1976): 1293-1295.  Bogard, D. D. & Johnson, P. (1983) Science, 221: 651–654.  Swindle, T. D., M. W. Caffee, and C. M. Hohenberg. Geochim et Cosmochim Acta 50.6 (1986): 1001-1015.  Pepin, Robert O. Icarus 111.2 (1994): 289-304.