4. Radiation

2005: IVA-5
2010: 2B
Priority: Medium

Investigation: Characterize in detail the ionizing radiation environment at the Martian surface, distinguishing contributions from the energetic charged particles that penetrate the atmosphere, secondary neutrons produced in the atmosphere, and secondary charged particles and neutrons produced in the regolith.

Calculations of the skin dose equivalent for astronauts on the surface of Mars near solar minimum. The variation in the dose with respect to altitude is shown. Image Credit: Saganti, et al 2004

Determining the amount and intensity of radiation that the surface of Mars receives is important for the safety of future astronauts potentially sent there. Such measurements and understanding would help characterize potential risks posed by ionization radiation, determine the type and amount of shielding required to protect the crew, and mitigate risks of radiation during Earth-Mars-Earth transit phase.

There are two main types of radiation that scientists are concerned with: Galactic Cosmic Rays (GCR) – high energy particles bombarding our solar system from across the universe - and Solar Energetic Particles (SEP) – lower energy but higher-concentrated particles generated periodically through Coronal Mass Ejections. On Earth, the atmosphere and magnetic field protect us from harmful radiation, but Mars has a significantly thinner atmosphere and no magnetic field. Radiation exposure would therefore be much higher on Mars, and high-energy particles could dissipate energy into the surface and create harmful secondary particles. Radiation dose varies with solar activity and GCR levels as well as the topography and surface properties of Mars, so we need accurate readings of radiation in the atmosphere as well as on the surface. Space weather predictions could help reduce the mass of shielding material by having people travel during a period of minimal radiation and giving adequate warning when CMEs occur.

2005 Version of Investigation (old version)

2010 Version of Investigation (current version)

The updates in the required measurements for this section are minimal, since there were not any advancements in the field since the 2005 revision. Measurement (a) was reworded to reflect that each particle species has a different relevant energy range, and the lower end of the energy range in (b) was altered because anything smaller than 10keV is not biologically significant. The article below gives an idea of the state of research in the field. There is currently work in progress to assess the episodic solar energetic particle fluxes and variability at Mars. MSL will carry a Radiation Assessment Detector (RAD) to measure GCR and SEP contributions to radiation on the surface over a two-year timeframe, although it is expected to obtain more information for GCR than for SEP.