As Perseverance begins its search for ancient life on the surface of Mars, new research suggests that the interior of the Red Planet may be a .

The study, published in the journal Astrobiology, examines the chemical composition of Martian meteorites, rocks that were lifted off the surface of Mars and eventually landed on Earth. Analysis has shown that these rocks if they are constantly in contact with water, will produce chemical energy. It is needed to support microbial communities like those that survive in the dark depths of the Earth. Since these meteorites may be representative of the vast swaths of the Martian crust, the findings suggest that most of Mars’ interior may be habitable.

In recent decades, scientists have discovered that the Earth’s interior is home to a vast biome that exists separately from the world above. Even without sunlight, these creatures survive by using the byproducts of chemical reactions that occur when rocks come into contact with water.

One such reaction is radiolysis, which occurs when radioactive elements in rocks react with water trapped in pores and cracks. The reaction splits water molecules into their constituent elements, hydrogen and oxygen. The released hydrogen dissolves in the remaining groundwater, while minerals such as pyrite (fool’s gold) absorb free oxygen to form sulfate minerals. Bacteria can consume dissolved hydrogen as fuel and use the oxygen stored in sulfates to “burn” it.

Such “sulfate-reducing” microbes are found in places such as the Kidd Creek mine in Canada. There they live 1,500 meters underground and have not been born for over a billion years. Scientists have sought to better understand these underground systems, with an eye on finding similar habitats on Mars and elsewhere in the solar system. The project, called Earth 4D: Subsurface Science and Exploration, is supported by the Canadian Institute for Advanced Study.

Scientists used data from NASA’s Curiosity rover and other orbiting spacecraft, as well as data on the composition of Martian meteorites representing various parts of the planet’s crust.

Scientists were looking for ingredients for radiolysis: radioactive elements such as thorium, uranium and potassium; sulfide minerals that can be converted to sulfates; and stone blocks with sufficient porous space to trap water. The study found that in several different types of Martian meteorites, all of the ingredients are present in sufficient quantities to support the Earth’s habitat. This is especially true of regolith breccias, meteorites mined from crustal rocks over 3.6 billion years old. They have the greatest potential to sustain life. Unlike Earth, Mars lacks a plate tectonics system that constantly recycles the rocks of the earth’s crust. Thus, these ancient landscapes remain largely intact.

The findings help substantiate an exploration program that looks for signs of modern life in the bowels of Mars.