Could Life Survive Beneath the Surface of Mars?

Short answer: possibly, but nobody knows yet. The surface of Mars is cold, dry, thin-aired and soaked in radiation. Underground the odds improve: radar and seismic data point to buried liquid water, salts keep brines liquid well below 0 °C, and on Earth whole ecosystems live kilometres down without sunlight. No life has been confirmed on Mars, past or present.

That gap between “possible” and “confirmed” is where NovaSeed: Eden Rising starts. In the novel, eighty-five centimeters below the surface of the Hellas Planitia basin, in a liquid brine pocket that has existed for four billion years, something is alive. This post separates the real science from the story.

Why is the surface of Mars so hard on life?

Mars has an atmosphere, but a thin one. Average surface pressure is about 6.1 millibars, under one percent of Earth’s. Without a global magnetic field or a thick atmosphere, ultraviolet light and cosmic radiation reach the ground. The soil is also chemically harsh. In 2008, NASA’s Phoenix lander found that 0.4 to 0.6 percent of the soil it analysed, by mass, was perchlorate, a reactive salt that can destroy organic molecules when heated or irradiated.

For that reason, planetary scientists expect the best-preserved organic material to sit below the surface, not on it. The European Space Agency designed the drill on its Rosalind Franklin rover to reach up to two metres down, past the layer most exposed to radiation and oxidants. Earlier missions sampled no deeper than about 15 centimetres.

Is there liquid water under Mars today?

Two lines of evidence suggest there may be, though neither is a direct sample.

• Radar under the south polar ice (2018). The MARSIS radar on ESA’s Mars Express detected an unusually bright reflection in a 20-kilometre-wide zone about 1.5 km beneath the south polar layered deposits. The team interpreted it as a body of liquid water, probably kept liquid by dissolved salts. Other researchers have questioned that, because the base of the ice should be around −68 °C and other materials can produce bright echoes.
• Seismic data from InSight (2024). Using marsquake measurements from NASA’s InSight lander, Wright, Morzfeld and Manga found that the mid-crust, about 11.5 to 20 km down, is best explained by fractured igneous rock saturated with liquid water. If that layer is typical of the planet, it could hold enough water to cover Mars to a depth of one to two kilometres.

The salts that make the surface hostile help here. Perchlorate and other salts lower the freezing point of water, so a brine can stay liquid at temperatures that would freeze pure water solid.

Why set a discovery in Hellas Planitia?

Hellas is the deepest basin on Mars, roughly 2,300 km across, with a floor about 7,152 m below the planet’s reference level. Depth means more air overhead. Mars Global Surveyor radio measurements recorded 11.5 millibars on the basin floor, and winter pressures reach about 12.4 millibars, roughly double the global reference and above the triple point of water.

A NASA-supported climate modelling study (Haberle and colleagues, 2001) identified Hellas as one of five regions where surface pressure and temperature periodically allow liquid water to exist briefly. The same study warns that fast evaporation means melting is probably rare. Hellas is not a wet place, but it is one of the least impossible places on the planet for liquid water. You can explore the basin’s place in the series on the Hellas coordinates page and the Mars Operations briefing.

What could live in the dark?

The strongest argument for subsurface life on Mars comes from Earth. In 2008, researchers sequencing fracture water 2.8 km down in South Africa’s Mponeng gold mine found that one bacterium, Desulforudis audaxviator, made up more than 99.9 percent of the microbes present. Its energy comes ultimately from radioactivity in the rock, which splits water molecules and produces the chemicals it feeds on. No sunlight is involved at any step.

In 2013, drilling into Subglacial Lake Whillans, about 800 m beneath the West Antarctic Ice Sheet, recovered an active microbial ecosystem living in permanent darkness and cold. Neither site is Mars, but both show that life needs water, an energy source and shelter more than it needs a sky.

Has anything actually been found on Mars?

Nothing alive. The findings so far are about ancient conditions and chemistry:

• NASA’s Curiosity rover found organic molecules preserved in mudstones about three billion years old in Gale Crater (Eigenbrode et al., 2018).
• In September 2025, a team reporting in Nature described a rock in Jezero Crater, nicknamed “Cheyava Falls,” with “leopard spot” reaction fronts containing the minerals vivianite and greigite next to organic carbon. NASA called the Sapphire Canyon core sample a potential biosignature. Similar minerals can form without life, and confirmation would need laboratory study of the sample on Earth.

Where does the science end and the story begin?

The novel moves the water far closer to the surface than any evidence suggests, and that is the fiction. The rest of the premise, that if Mars has life it is most likely hiding underground in salty water, follows mainstream astrobiology. For how SOLEN logged the discovery in-world, read The Real Science Behind the Hellas Planitia Discovery, and for the mission AI’s private account of the anomaly at 85 centimetres, see SOLEN: The First Record. The first confirmed chemical exchange between Earth and Martian life comes later, in Children of Dust.

If you came here from The Martian or Project Hail Mary, our guides to books like The Martian and books like Project Hail Mary explain how the series compares. New readers can read chapter one free or check the reading order.

NovaSeed: Eden Rising and the SOLEN: The Eden Archive series are fiction. Scientific statements in this post are linked to their sources below; story details are labelled as the novel’s.