Noble gases and nitrogen in Tissint reveal the composition of the Mars atmosphere

Abstract

Comparative planetology is crucial to unravel the origin and evolution of volatile elements on terrestrial planets. We report precise measurements of the elemental and isotopic composition of nitrogen and noble gases in the Martian meteorite Tissint. Ar-N 2 correlations confirm discrepancies between results from Viking and Martian meteorites and those from the Mars Science Laboratory (MSL) mission. The Martian atmospheric 40 Ar/ 36 Ar ratio is estimated to be 1714 ± 170 (1σ), lower than the value determined by Viking but in agreement with, and with higher precision than, data from MSL. We confirm a solar wind-like origin for Martian Kr and Xe. Excesses on light Kr isotopes are lower than those measured by MSL. Cosmogenic excesses in the Xe isotopic spectrum could have been produced in space during exposure of the Tissint parent body to cosmic rays.

Heavy halogen geochemistry of martian shergottite meteorites and implications for the halogen composition of the depleted shergottite mantle source

“…The samples were fully degassed in the main temperature steps, as shown with re-extraction steps at slightly elevated temperature. The natural noble gas isotope composition of Tissint is reported by Wieler et al (2016) and Avice et al (2018) and is therefore not repeated here.…”

The history of the Tissint meteorite, from its crystallization on Mars to its exposure in space: New geochemical, isotopic, and cosmogenic nuclide data

“…The cobalt concentration in Tissint was measured to be 63.2 ppm (Avice et al. ), which is lower by about a factor of 10 when compared to H chondrites (Wasson and Kallemeyn ). The measured 60 Co limits (<0.2 dpm kg −1 for the large fragment and <1.9 dpm kg −1 for the small one, which is higher only due to small statistics), imply that in the case of Tissint, the 60 Co method is not useful for the determination of its radius.…”

“…Figure shows calculated 26 Al production rates for different radii of the Tissint meteorite following the Monte Carlo model of Leya and Masarik (), adjusting for its chemical composition of 21% of Si and 2.4% of Al (Avice et al. ). The measured 26 Al activity (36.2 ± 1.3 dpm per kg for the large fragment) shown in Fig.…”

“…The CRE can be calculated from the equation A = P(1Àe -kT ), where A is the cosmogenic radionuclide activity, P is its production rate in the meteorite by cosmic-ray particles, k is the decay constant, and T is the time of the meteorite irradiation equal to its CRE age. Figure 7 shows calculated 26 Al production rates for different radii of the Tissint meteorite following the Monte Carlo model of Leya and Masarik (2009), adjusting for its chemical composition of 21% of Si and 2.4% of Al (Avice et al 2018). The measured 26 Al activity (36.2 AE 1.3 dpm per kg for the large fragment) shown in Fig.…”

Perspectives on Atmospheric Evolution from Noble Gas and Nitrogen Isotopes on Earth, Mars & Venus

“…It is only 2.4 %/u when the direct measurement of the atmosphere by the Mars Sample Laboratory's mass spectrometer(Conrad et al 2016) is considered. The difference between these two values could be due to potential spallation excesses on light Xe isotopes for the latter, but the debate remains open(Avice et al 2018a; Conrad et al 2016). In any case, the extent of fractionation is comparable for Mars and Earth.Having a similar isotopic fractionation for atmospheric Xe on Mars and Earth is striking.Indeed, the escape process proposed byZahnle et al (2019) depends on parameters such as the gravity of the body, the ionization rate of Xe in the atmosphere and the Solar irradiation activity, and probably the strength and shape of the magnetic field since Xe escapes as ions.All these parameters have different values on Earth and Mars and some of them have also varied with time.…”