From the Top of Martian Olympus to Deep Craters and Beneath: Mars Radiation Environment Under Different Atmospheric and Regolith Depths

Abstract

In preparation for future human habitats on Mars, it is important to understand the Martian radiation environment. Mars does not have an intrinsic magnetic field and Galactic cosmic ray (GCR) particles may directly propagate through and interact with its atmosphere before reaching the surface and subsurface of Mars. However, Mars has many high mountains and low‐altitude craters where the atmospheric thickness can be more than 10 times different from one another. We thus consider the influence of the atmospheric depths on the Martian radiation levels including the absorbed dose, dose equivalent and body effective dose rates induced by GCRs at varying heights above and below the Martian surface. The state‐of‐the‐art Atmospheric Radiation Interaction Simulator based on GEometry And Tracking Monte Carlo method has been employed for simulating particle interactions with the Martian atmosphere and terrain. We find that higher surface pressures can effectively reduce the heavy ion contribution to the radiation, especially the biologically weighted radiation quantity. However, enhanced shielding (both by the atmosphere and the subsurface material) can considerably enhance the production of secondary neutrons which contribute significantly to the effective dose. In fact, both neutron flux and effective dose peak at around 30 cm below the surface. This is a critical concern when using the Martian surface material to mitigate radiation risks. Based on the calculated effective dose, we finally estimate some optimized shielding depths, under different surface pressures (corresponding to different altitudes) and various heliospheric modulation conditions. This may serve for designing future Martian habitats.

The Zenith‐Angle Dependence of the Downward Radiation Dose Rate on the Martian Surface: Modeling Versus MSL/RAD Measurement

“…However, when considering the full sky view, that is, integrating over all zenith angles, this difference is only about 10% as explained in Section 3.2. Moreover, previous model results show that HZE ions contribute about 10% to the total dose on the surface of Mars (Röstel et al., 2020; Zhang et al., 2022) when considering particles arriving from the full sky view. We expect that this discrepancy between 28% and 10% is due to the fragmentation of HZE particles at large zenith angles because such particles need to traverse a significantly larger column depth.…”

Modeling the Radiation Environment of Energetic Particles at Mars Orbit and a First Validation against TGO Measurements

“…It can offer detailed Martian atmospheric characteristics, such as temperature, density, and compositions, at different altitudes, different seasons, and even different times of the day on Mars (Lewis et al 1999). Zhang et al (2022) have investigated how atmospheric thickness affects particle interactions at different altitudes and locations on Mars. By selecting six positions with different surface pressures: 82, 305, 529, 753, 975, and 1200 Pa, they have simulated the particle fluxes of the interaction between the GCRs and the Martian atmosphere at an altitude up to 70 km, and revealed the atmosphere above 70 km played a negligible role in the interaction with the propagating GCR particles.…”

“…Due to the lack of a global intrinsic magnetic field (Acuna et al 1999), energetic particles propagating in interplanetary space can directly reach the atmosphere of Mars and even arrive at its surface, thus making Mars more exposed to the space radiation environment impact (see a recent review by Guo et al 2021, and references therein). The surface pressure of Mars is generally less than 1% of that of Earth, ranging from only 82 Pa to about 1200 Pa (see, e.g., Figure 2 of Zhang et al 2022). When energetic particles enter the Martian atmosphere, they may lose energy and generate secondary radiation due to their interactions with the atmosphere, such as ionization, inelastic scattering and fragmentation, etc.…”

“…In addition to the in situ observations, there have been numerous modeling studies of the Martian radiation environment, which are generally based on the GCR models and particle transport codes (e.g., De Angelis et al 2006;Sato et al 2008;McKenna-Lawlor et al 2012;Kim et al 2014;Gronoff et al 2015;Hassler et al 2017;Guo et al 2018;Röstel et al 2020;Zhang et al 2022). Specifically, various particle transport codes such as HZETRN (High charge (Z) and Energy TRaNspor, Wilson et al 1991;Slaba et al 2010), MARSREC (MARS Radiation Environment Characterization, Keating et al 2005), PLANETOCOSMICS (Desorgher 2005), PHITS (Particle and Heavy Ion Transport code System, Niita et al 2006;Sato et al 2018), MEREM (Mars Energetic Radiation Environment Model, Gonçalves et al 2009;Gonćalves et al 2022), MCNP6 (Monte Carlo NParticle transport code, Goorley et al 2012;Werner et al 2017), and the most recent AtRIS (Atmospheric Radiation Interaction Simulator, Banjac et al 2018;Guo et al 2019) can be applied to investigate particle interactions with the Mars's atmosphere.…”

The archaeal class Halobacteria and astrobiology: Knowledge gaps and research opportunities

“…This is in stark contrast with the large amount of information already available about Mars and its apparently unwelcoming conditions. These are particularly harsh to mesophiles, combining high levels of radiation (particularly ultra-violet UVC and UVB) ( Cockell et al, 2000 ; Vicente-Retortillo et al, 2020 ; Zhang et al, 2022 ), desiccation/low water activity ( Knoll and Grotzinger, 2006 ; Stevenson et al, 2015b ; Toner and Catling, 2018 ; Rivera-Valentín et al, 2020 ; Hallsworth et al, 2021a ), high concentrations of salts and volatile oxidants induced by radiation ( Quinn et al, 2013 ; Lasne et al, 2016 ; Wu et al, 2018 ), locations with acidic conditions ( Benison and Bowen, 2006 ; Bibring et al, 2006 ; Noe Dobrea and Swayze, 2010 ; Ehlmann et al, 2016 ), solar particle events ( Lillis and Brain, 2013 ; Ramstad et al, 2018 ), low temperatures, low pressures ( Pätzold et al, 2016 ; Spiga et al, 2018 ), and low nutrient availability ( Tomkins et al, 2019 ; Fackrell et al, 2021 ; Tarnas et al, 2021 ). Although the extreme setting of Mars has traditionally been seen as biocidal, this is not necessarily the case, as recently highlighted by Hallsworth (2021) .…”