Discovery: Radiation exposure at the martian surface is about two and one-half times that in the International Space Station.
Significance: Affects how deeply beneath the surface life might be found on Mars, and what challenges humans will face to survive there.
Images: NASA/JPL/Johnson Space Center
Estimated radiation dose from galactic cosmic rays (GCR) on the
martian surface, from MARIE orbital radiation data and MOLA laser altimetry. The
lower the altitude, the lower the expected dose, because the atmosphere provides
Without a global magnetic field and with little atmosphere to provide shielding, the surface of Mars is bombarded by two types of primary radiation. Solar flares are bursts of low-energy protons from the Sun; they are intermittent and relatively easy to shield against. Galactic cosmic rays (GCR) are extrasolar, high-energy atomic nuclei that damage DNA; they are continuous and cannot be shielded against, so determining the dosage an astronaut would receive is necessary prior to any human exploration. Mars Odyssey’s Mars Radiation Environment Experiment (MARIE) provided the first direct information about the martian radiation environment. It found radiation exposure at the martian surface to be about two and a half times that at the International Space Station, in agreement with calculated values.
Zeitlin, C. et al. (2004). Overview of the Martian radiation environment experiment. Adv. Space Res. 33, 2204-2210.
Image: courtesy Donald Hassler
Coverage by the MSL RAD instrument suite. Image: NASA, courtesy Donald Hassler
If life ever evolved on Mars, it may still exist below ground, shielded from radiation and radiation-produced oxidants. The Mars Science Laboratory will characterize primary and secondary surface radiation, including particles, x-rays, gammas, and 200-400 nm UV. The data will aid assessment of whether the martian surface is sterile, and calculation of the minimum depth needed to drill to look for any surviving life.
• Hassler, D.M. et al. (2009). The Radiation Assessment Detector
(RAD) on the Mars Science Laboratory (MSL). Paper contributed to the 40th Lunar
and Planetary Science Conference, March 23-27 2009, The Woodlands TX. Sponsored
by the Lunar and Planetary Institute, Houston TX. Retrieved from http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2297.pdf.
• Gomez-Elvira, J. et al. (2008). Environmental Monitoring Station for Mars Science Laboratory. Paper contributed to the 3rd workshop on The Mars Atmosphere: Modeling and Observations, November 10-13 2008, Williamsburg VA. Sponsored by the Lunar and Planetary Institute, Houston TX. Retrieved from http://www.lpi.usra.edu/meetings/modeling2008/pdf/9052.pdf.
• Committee on Precursor Measurements Necessary to Support Human Operations on the Surface of Mars, National Research Council. Safe on Mars: Precursor Measurements Necessary to Support Human Operations on the Martian Surface. Washington, D.C.: National Academy Press, 2002. Retrieved from http://www.nap.edu/catalog/10360.html