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Carbonaceous Chondrite Outgassing Experiments to Constrain the Formation of Titan’s Atmosphere

Presentation #218.03 in the session “Titan Surface and Interior”.

Published onOct 26, 2020
Carbonaceous Chondrite Outgassing Experiments to Constrain the Formation of Titan’s Atmosphere

The origin of Titan’s thick N2 and CH4 dominated atmosphere is an outstanding puzzle in planetary science. Photochemical models predict that Titan’s current atmospheric methane would be quickly destroyed by photolysis in ~30 million years [1], suggesting a possible need for a mechanism to replenish the methane [2].  One potential mechanism has been linked to the interior composition and structure of Titan, and to better understand this question of methane persistence in the atmosphere, we turn to Titan’s atmospheric formation [3].  Titan’s atmosphere may have been produced in part from interior outgassing with evidence coming from the detection of outgassed 40Ar, a radiogenic decay product of 40K, that was detected by the Huygens Gas Chromatograph and Mass Spectrometer [4]. Recent studies suggest that organic material similar to the refractory organics found in comets may be a necessary component of Titan’s interior, and outgassing of such material could provide significant amounts of N2 and CH4 to replenish Titan’s atmosphere [5][6].  For this study, we analyze carbonaceous (CM) chondrites because they contain insoluble organic matter (IOM), which is similar to cometary refractory organics and may serve as an analog to part of the interior material of Titan.  In particular, we studied samples from the Murchison meteorite because it is a pristine CM carbonaceous chondrite fall with a significant IOM component.  We performed a suite of stepped heating experiments that will help place experimental constraints on the amounts of outgassed carbon and nitrogen compounds from CM chondrites to help inform the outgassed origin and composition of Titan’s atmosphere.   We performed these experiments on powdered Murchison samples with two grain size distributions, one including grains between 20-100 microns in diameter and the other with grain diameters <20 microns.  We present the results of our stepped heating experiments in which we heated these powdered samples up to 1200 C in a furnace connected to a residual gas analyzer (RGA) that continuously monitored the partial pressures of 10 different outgassed species (e.g., C, CO, CO2, CH4, N, N2).  By measuring the abundances of outgassed volatiles, we compare our results to prior experimental work on IOM from carbonaceous chondrites and discuss how these experiments will inform the outgassing origin and composition of Titan’s atmosphere.

  1. Yung, Y. L., et al. 1984. ApJ., 55.

  2. Hörst, S. M. 2017. J. Gphys Res., 122.

  3. Nixon, C., et al, 2018. Pl. Sp. Sci., 155.

  4. Niemann, H.B., et al. 2005. Nat. 438.

  5. Miller, K. E., et al. 2019. ApJ., 871.

  6. Néri, A., et al. 2019. E. Pl. Sci Lts, 530.

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