Mars: how to reduce the effect of cosmic rays using the rock and sediments of the red planet

The use of natural materials such as rock and sediments on Mars could offer some protection against space radiation that affects the red planet as it lacks a magnetic field.

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This is the conclusion of a study based on data from the RAD (Radiation Assessment Detector) instrument aboard NASA’s Curiosity rover, obtained while the vehicle was parked against a cliff at a place called “Murray Buttes” from September 9 to 21, 2016.

What the RAD detected on Mars

While there, RAD measured a 4% decrease in overall radiation. More significantly, the instrument detected a 7.5% decrease in radiation from neutral particles, including neutrons that can penetrate rock and are especially harmful to human health.

These numbers are statistically high enough to show that it was due to Curiosity’s location at the foot of the cliff and not due to normal changes in background radiation.

“We’ve been waiting for a long time for the right conditions to get these results, which are critical to ensuring the accuracy of our computer models,” said Bent Ehresmann of the Southwest Research Institute, lead author of the paper, recently published in JGR Planets. “At Murray Buttes, we finally had these conditions and the data to analyze this effect. Now we are looking for other locations where RAD can repeat this type of measurements ”.

Where does the radiation measured by RAD come from on Mars

Most of the radiation measured by RAD comes from galactic cosmic rays – particles ejected by exploding stars and sent like pinballs throughout the universe. This forms a carpet of “background radiation” that can pose health hazards to humans.

Much more intense radiation comes sporadically from the Sun in the form of solar storms that hurl massive arcs of ionized gas into interplanetary space.

“These structures twist in space, sometimes forming complex croissant-shaped flux tubes larger than Earth, generating shock waves that can efficiently energize particles,” said Jingnan Guo, who led a study, published in September in The Astronomy and Astrophysics Review, which analyzed nine years of RAD data while at Christian Albrecht University in Germany.

“Cosmic rays, solar radiation, solar storms, are all components of space weather, and RAD is effectively a space weather outpost on the surface of Mars,” says Don Hassler of the Southwest Research Institute, principal investigator of the RAD instrument. .

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How solar activity affects Mars

Solar storms occur with a variable frequency based on 11-year cycles, with certain cycles supporting more frequent and energetic storms than others. Contrary to intuition, periods when solar activity is at its highest may be the safest time for future astronauts on Mars: increased solar activity protects the red planet from cosmic rays between 30 and 50%, compared to periods when solar activity is lower.

“It is compensation,” Guo said. “These periods of high intensity reduce one source of radiation: the ubiquitous high-energy cosmic-ray background radiation around Mars. But at the same time, astronauts will have to deal with the most intense intermittent radiation from solar storms. “

“RAD observations are key to developing the ability to predict and measure space weather, the influence of the Sun on Earth and other bodies in the solar system,” said Jim Spann, space weather leader for NASA’s Heliophysics Division. . “As NASA plans human voyages to Mars, RAD serves as an outpost and part of the Heliophysical System Observatory, a fleet of 27 missions investigating the Sun and its influence in space, whose research supports our understanding and exploration. from space”.

RAD has measured the impact of more than a dozen solar storms to date (five while traveling to Mars in 2012), although these past nine years have marked an especially weak period of solar activity.

What are class X solar flares

Scientists are beginning to see an increase in activity as the Sun comes out of its slumber and becomes more active. In fact, RAD observed evidence of the first class X eruption of the new solar cycle on October 28, 2021. Class X eruptions are the most intense category of solar flares, the largest of which can cause power outages and communications outages on Earth.

“This is an exciting time for us, because one of RAD’s important goals is to characterize the extremes of space weather. Events like solar flares and storms are a type of space weather that occurs most frequently during increased solar activity – the time is getting closer now, ”Ehresmann said. More observations are needed to assess the danger of a really powerful solar storm to humans on the Martian surface.

The RAD findings will feed into a much larger data set that will be collected for future manned missions. In fact, NASA even outfitted Curiosity’s counterpart, the Perseverance rover, with samples of space suit materials to assess how they resist radiation over time.

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