¹Sarah Joiret, ^1,2Alessandro Morbidelli, ³Rafael de Sousa Ribeiro, ⁴Guillaume Avice, ⁵Paolo Sossi
Eartha and Planetary Science Letters 671, 119625 Link to Aricle [https://doi.org/10.1016/j.epsl.2025.119625]
¹Collège de France, Université PSL, 75005 Paris, France
²Laboratoire Lagrange, Université Cote d’Azur, CNRS, Observatoire de la Côte d’Azur, Boulevard de l’Observatoire, 06304 Nice Cedex 4, France
³Sao Paulo State University, UNESP, Campus of Guaratingueta, Av. Dr. Ariberto Pereira da Cunha, 333 – 6 Pedregulho, Guaratingueta – SP, 12516-410, Brazil
⁴Université Paris Cité, Institut de physique du globe de Paris, CNRS, 75005 Paris, France
⁵Institute of Geochemistry and Petrology, ETH Zürich, Sonneggstrasse 5, CH-8092 Zürich, Switzerland
Copyright Elsevier

Mars finished forming while the solar nebula was still present, and acquired its primordial atmosphere from this reservoir. The absence of a detectable cometary xenon signature in the present-day Martian atmosphere suggests that the capture of solar nebular gas was significant enough to dilute later cometary contributions. By quantifying the mass of cometary material efficiently retained on Mars, we place a lower bound on the mass of the primordial Martian atmosphere. To test the robustness of our conclusions, we use cometary bombardment data from two independent studies conducted within a solar system evolutionary model consistent with its current structure. Our calculations show that, even under the most conservative scenario, the minimal mass of the primordial martian atmospheres would yield a surface pressure of no less than 2.9 bar. Such a massive nebular envelope is consistent with recent models in which atmospheric capture is strongly enhanced by the presence of heavier species on Mars – due to outgassing or redox buffering with a magma ocean.