What if there were natural protections against cosmic rays on Mars?

A short time ago we told you about the radiation problem on Mars and the difficulty for a possible human team to stay on the planet for more than four years without suffering serious damage. Without a protective magnetic shield and an atmosphere as thick as Earth's, radiation from space has an almost barrier-free path to the Martian surface. However, a new study using data from the Mars Science Laboratory (MSL) Curiosity has discovered how the features of Mars' natural landscape can provide shelter from radiation. In particular, it shows how the so-called Martian butte - small isolated hills, which also exist on Earth - can provide protection from high-energy particles from space.

The study, entitled “Directionality of the Martian Surface Radiation and Derivation of the Upward Albedo Radiation ”was published in Geophysical Research Letters. The lead author is Guo Jingnan of the University of Science and Technology of China. When MSL Curiosity landed on the surface of Mars in 2012, it carried in its payload an instrument called the Radiation Assessment Detector (RAD), which can detect and measure harmful radiation on Mars that comes from the Sun and other sources. Among the areas studied there is precisely the Murray Buttes region, on the lower Mount Sharp, in the Gale crater.

The data collected showed that near the butte there was a reduction in the radiation dose of about 5 %, but they obviously couldn't explain why. The explanation is rather complex and depends on the characteristics of the planet, essentially devoid of atmosphere. Basically the radiation hitting things, or people, on the surface of Mars comes from space, but some of it is albedo radiation, which means it is reflected off the surface, hitting objects from below.

Man on Mars, graphic illustration. In short, the radiation dose on the surface of Mars is not consistent, but it fluctuates and the heliospheric changes can affect its trend, as well as the angle of the sky to which any explorer can be exposed. A steeper angle means that the radiation has to travel through more atmosphere, which changes the surface exposure.

The orbit of Mars changes its distance from the Sun, which also affects surface radiation. Lower altitudes will be exposed to less radiation than higher altitudes. And the radiation is not a homogeneous phenomenon: there are protons, alpha particles, ions of various elements, neutrons and gamma rays.

Overall, the study helps to paint a more complete picture of the Martian radiation environment. There is already a lot of talk about placing bases in lava tubes, where people would be protected by meters of Martian regolith. But astronauts can't spend all their time there. They will have to venture into radiation. Detailed radiation maps that take into account the exposure of the sky and the ground and anything else could therefore save lives.