Space Radiation studies for safe Mars missions
Space radiation is one of the main factors affecting survivability and habitability conditions. At Mars, as well as during the travel to it, the radiation environment is mostly constituted by Galactic Cosmic Rays (GCRs), the highly energetic low intensity background believed to be associated to supernovae explosions, and Solar Energetic Particles (SEPs), linked to transient events on the Sun.
In the first step of the mission close to Earth, trapped radiation in the Van Allen belts plays the major role. All this radiation, impacting on a spacecraft or at the top of Martian atmosphere, can generate considerable secondary radiation and particles showers, that can affect astronauts and future explorers on Mars, breaking bonds in biomolecules, and/or affect several components of a spacecraft.
Overall, the study of radiation-induced effects spans a wide concept of habitability, as such effects could affect not only crewed missions but also eventual life forms or their traces on other bodies, as well as assets and components needed for safe missions.
Radiation at Mars mission landing sites
In collaboration with staff from NASA LRC and the Curiosity rover team, the ESC2RAD team recently studied the radiation environment and induced doses by GCRs and SEPs, at two sites of major astrobiological interest on Mars in the northern hemisphere:
- Oxia Planum, the landing site of the ExoMars 2022 ESA’s mission
- Mawrth Vallis, a previous candidate site under scrutiny for several missions.
Space radiation targets
Using Monte Carlo particle transport approaches and considering water as proxy for biological targets, we found
- a different amount of gamma radiation according to the different level of hydration of the regolith at the two sites
- a slightly different relation between doses and surface pressure during different seasons and under different solar activity, with respect to the data by Curiosity at Gale Crater, in the southern hemisphere.
This means that even simply considering a water target, there are still lessons to learn on how the radiation environment at Mars varies during different seasons and on how the hydration of the regolith influences neutron reactions that lead to gamma radiation.
An important step in the modelling of radiation effects is however to consider more realistic targets, like small biological units instead of the sole water, and to study in detail the pattern of energy release to the biomolecule by the impacting particle (and by secondaries causing water hydrolysis), the so-called track structure.
In this context, the ESC2RAD project:
- has developed a new smart and efficient strategy to probe all the relevant trajectories of protons in the surrounding water
- is now calculating fundamental nanodosimetric quantities in glycine (the simplest amino acid) and DNA segments, aiming at extending the capabilities of Monte Carlo track structure codes and advance the understanding of radiation physics
- is studying new materials solutions to allow for a better radiation-protection
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