Radiation Environment and Doses on Mars at Oxia Planum and Mawrth Vallis: Support for Exploration at Sites With High Biosignature Preservation Potential. Issue 1 (26th January 2021)

• Record Type: Journal Article
• Authors: Da Pieve, F.; Gronoff, G.; Guo, J.; Mertens, C. J.; Neary, L.; Gu, B.; Koval, N. E.; Kohanoff, J.; Vandaele, A. C.; Cleri, F.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 1(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-01-26
• Subjects: Oxia Planum -- radiation -- regolith -- astrobiology -- human planetary exploration; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1029/2020JE006488
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: The first human missions on Mars will likely involve several astrobiology‐driven science operations, at sites with high biosignature preservation potential. Here, we present a study of the radiation environment induced by Galactic Cosmic Rays and Solar Energetic Particles at Oxia Planum, landing site of the European Space Agency ExoMars 2022 mission, and at two different locations in Mawrth Vallis, using the Monte Carlo GEometry ANd Tracking 4‐based code dMEREM (detailed Martian Energetic Radiation Environment Model). The radiation environment for solar minimum in 2009 and a period close to solar maximum during the declining phase of solar cycle 23 appears similar at the different sites, with the deepest Mawrth Vallis location having a slightly enhanced γ ‐ray contribution, due to a higher modulation of fast neutrons by the more water‐rich regolith. The comparison with the Dose Equivalent from an updated extrapolation of 7+ years data from the Radiation Assessment Detector (RAD) onboard the Curiosity rover highlights the importance of input modulation conditions, some drawbacks of the galactic cosmic ray model used here, and the need to include heavy ions, the three aspects affecting differently the estimations for solar maximum and minimum. The dependence of doses on surface pressure highlights a possible influence of the different dust loading at the different sites. Estimated exposure levels for a 1‐year stay and for a short stay in Arabia Terra, the latter including a October 28, 2003 event with a fluence an order of magnitude higher than the relevant September 2017 event detected by RAD, leave reasonable to large safety margins. Plain Language Summary: Space radiation is caused by high‐energy particles coming from the Sun or further away. Such radiation is dangerous for humans since they can cause cancers. At Earth, we are protected by a relatively thick atmosphere and by the global magnetic field, but the first explorers of Mars will be subject to higher radiation exposure. In this paper, we compute the risks caused by these radiations at Oxia Planum, the landing site of the ExoMars 2022 mission, and Mawrth Vallis, previously under scrutiny by NASA and European Space Agency, both in the northern hemisphere. We modeled different conditions of space radiation (which is determined by the activity of the Sun) and we considered the effect of the ground composition on the results. The model results are compared with the estimations of the radiation at the ground based on the observations by the Curiosity rover located at the Gale crater in the Southern hemisphere. We show that locations rich in water may have more gamma rays. We show that the risks are moderate when considering the radiation exposure limits recommended for Low Earth Orbit. Key Points: We study the radiation environment induced by galactic and solar radiation at Oxia Planum and Mawrth Vallis, for solar maximum/minimum Doses for solar maximum/minimum and their variation on surface pressure are compared to an updated analysis of Radiation Assessment Detector (RAD) data and previous results Slightly different water amounts in the regolith affect backscattered gamma‐rays; exposure for long/short stays implies moderate/low risk