Safe on Mars Precursor Measurements Necessary to Support Human Operations on the Martian Surface (2002) / Chapter Skim
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3. Physical Environmental Hazards
3. Physical Environmental Hazards
Pages 15-27
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From page 15... ...
The Martian regolith is 15 the complex outer layer of fractured rock and soil on the surface of Mars. This is the material that will support astronauts and roving vehicles as they traverse the Martian surface.
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From page 16... ...
The Need for Measurements To ensure safe landing and operations on the surface of Mars, it is necessary for NASA to fully characterize the landing site and the topography of the anticipated surface operation zone with high-resolution stereoscopic imaging. The operation zone is the area around the landing site defined by the anticipated range of operations of EVAs, including the use of human transport and/or science rovers.
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From page 17... ...
For long surface stays with multiple EVAs, space suit boots would be worn down by the process of walking over the Martian regolith. Rock abrasion would probably be more apparent on heavy science and human transport rover wheels, where sharp rocks might gouge grooves in the wheels.
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From page 18... ...
Recommendation: To ensure that humans and critical rover systems can land on and traverse the Martian surface in a safe, efficient, and timely manner, NASA should characterize the range of mechanical properties of the Martian regolith at the landing site or comparable terrain. Specifically, in situ experiments should be performed to determine the regolith's aggregate strength, stability, and sinkage properties, including bearing strength, bulk modulus, yield strength, and internal friction angle.
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From page 19... ...
The hazard presented by dust intrusion is more crucial for long stays on the Martian surface, where critical systems are exposed to the environment for a much longer time. Dust Adhesion Airborne dust on Mars will accumulate on surfaces by a wind-driven process abetted by electrostatic adhesion, magnetic attraction, or other adhesive properties such as the adhesion resulting from van der Waals (i.e., intermolecular)
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From page 20... ...
Thus, there would be no large electric potential differences between parts of the cloud and between the dust cloud and the Martian surface (Kolecki and Landis, 1966~. Although some electrical activity in Martian dust storms and dust devils should be anticipated, its intensity is not expected to be comparable to that of terrestrial lightning storms.
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From page 21... ...
Furthermore, neither the Viking missions nor the Mars Pathfinder mission experienced any problems due to electrostatic charging. While it would be useful to learn more about the electrical activity in Martian and terrestrial dust storms and vortices, the committee concludes that such increased knowledge is not essential for planning the first human mission to Mars.
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From page 22... ...
The Need for Measurements The committee believes that in light of the relatively low dynamic pressures experienced on Mars, no further characterization of wind speed on Mars is required prior to the first human mission. It believes that the surface winds are sufficiently characterized based on Viking and Pathfinder data and atmospheric dynamic models with regard to speed (based on Viking and Pathfinder experience)
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From page 23... ...
However, absorption and reradiation by the Martian regolith will alter the spectrum of the radiation environment. The radiation dose received by astronauts on the surface of Mars will be a significant fraction of the total radiation exposure for the mission.
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From page 24... ...
There have been no direct measurements of the radiation environment on the surface of Mars. Rather, the radiation environment is estimated using computer codes that model the transport of the deep space radiation through the Martian atmosphere and its interactions with the Martian surface.
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There has been some concern that localized concentrations of hydrogen in subsurface ice or hydrated minerals or iron within iron-rich rocks in the Martian regolith could skew the results of in situ testing for absorbed radiation dose if such testing is restricted to a small, localized area. At the comm~ttee's request, scientists at NASA Langley Research Center ran model simulations testing the effects of hydrogen and iron concentrations on absorbed dose.
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From page 26... ...
Recommendation: In order to validate the radiation transport codes, thereby ensuring the accuracy of radiation dose predictions, NASA should perform experiments to measure the absorbed dose in a tissue-equivalent material on Mars at a location representative of the expected landing site, including altitude and bulk elemental composition of the surface. The experiments should distinguish the radiation dose contribution induced by charged particles from that induced by neutrons.
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From page 27... ...
1966. "Electrical Discharge on the Martian Surface," November, available at |
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