The search for life on Mars and moons across the Solar System may need to start digging a bit deeper to find answers underground. Beneath the surface of these planetary bodies, there’s a chance that biological activity is being energized by cosmic rays flowing through space.
A new study published in the International Journal of Astrobiology suggests that cosmic rays can lay the groundwork for microscopic life to thrive in certain extraterrestrial environments. While cosmic radiation can inflict a range of harmful effects on humans, on the flip side, it also likely drives life-sustaining chemical reactions on Mars, Saturn’s icy moon Enceladus, and Jupiter’s moon Europa. All of these places, as a result, may be home to life beneath the surface.
Radiation Across the Universe
In space, there's no escaping cosmic rays. They’re constantly speeding across the universe, hailing from all over. Some come from the sun, while others are emitted by black holes and exploding stars from faraway galaxies.
The particles in cosmic rays — mostly consisting of hydrogen — hit planets and moons in our Solar System. Luckily, since Earth boasts a protective magnetic field and atmosphere, it's able to ward off most cosmic rays.
People are generally safe from cosmic radiation on Earth’s surface, but the real dangers kick in beyond the upper atmosphere. Once astronauts reach low-Earth orbit, radiation can cause central nervous system issues and increase the lifetime risk of developing cancer.
Unlike Earth, Mars lacks a global magnetic field and has a very thin atmosphere, and so its surface is inundated with particles that can penetrate underground. Given the hazards posed by cosmic rays to humans, they remain a major concern for future crewed missions to the Red Planet.
Read More: NASA's Europa Clipper Will Probe for Life in The Plumes of Icy Moons
The Life-Giving Potential of Cosmic Rays
Cosmic rays aren’t always so destructive, however. The new study indicates that when they hit water or ice underground, they release electrons that can become building blocks for microscopic life. Some bacteria on Earth use electrons for energy without the need for nutrients like sugars, sustained through a process called radiolysis.
Radiolysis of liquid water causes it to be broken down into molecules, and this process can occur in dark and cold environments that receive no sunlight. Since liquid water likely exists underneath the surface of Mars, Enceladus, and Europa, the researchers involved with the study wanted to determine the effects of cosmic rays on each of the planetary bodies.
Going Underground to Search for Life
Using computer simulations to calculate the energy deposition and electron production rates of radiolysis, the researchers found that metabolic activity could be sustained at certain depths of all three bodies. They say that Enceladus has the most potential to support life, followed by Mars, and then Europa.
This study dismantles previous views that life must always rely on sunlight or volcanic heat to exist.
“This discovery changes the way we think about where life might exist,” said lead author Dimitra Atri, Principal Investigator of the Space Exploration Laboratory at New York University Abu Dhabi, in a statement. “Instead of looking only for warm planets with sunlight, we can now consider places that are cold and dark, as long as they have some water beneath the surface and are exposed to cosmic rays. Life might be able to survive in more places than we ever imagined.”
Normally, the search for extraterrestrial life focuses on a “Goldilocks Zone,” the area around a star where a planet could have liquid water on its surface. However, now the search can extend to a region that the study calls the “Radiolytic Habitable Zone,” areas where water exists underground and can be energized by cosmic radiation.
This opens up a whole new world of possibilities for scientists on the hunt for life beyond Earth. Rather than being limited to the surfaces of planets and moons, they can now broaden their inspection to cover darker and colder places in space that may just hold a glimmer of hope for life.
Read More: Constantly Changing Ice on Jupiter's Moon Europa Hints at Possible Ocean and Life
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
International Journal of Astrobiology. Estimating the potential of ionizing radiation-induced radiolysis for microbial metabolism on terrestrial planets and satellites with rarefied atmospheres
The University of Chicago. Cosmic Rays, Explained
The Planetary Society. Mars may host oceans’ worth of water deep underground
Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.
