We haven't found aliens living on Mars. But a new study suggests we might be looking in the wrong place.
Since NASA's Viking spacecraft landed on the red planet in 1976, we've been searching for signs of life there -- even a microbial version. To date, there have been six missions that have successfully landed on Mars. None has found any life.
It makes sense. There may have been living organisms on our Earth-like neighbor in the distant past, but in its current state, life as we know it would not survive. For one thing, it's lethally cold. The average temperature on Mars is -80 degrees Fahrenheit. And there's no liquid water, essential for life. In fact, the atmospheric pressure is so low, any water that might appear would evaporate or freeze instantly -- the surface can't support water in a liquid state. Add to that, there's no breathable oxygen and the soil is toxic (apparently it contains perchlorate, highly reactive salts that would kill most life on Earth).
If all that wasn't enough to keep you from moving to Mars, there's also constant bombardment from lethal radiation. Mars lacks the magnetic field and thick atmosphere enjoyed by Earth. Anyone on the surface is left unprotected against the shower of cosmic rays. High-energy radiation from the sun would quickly destroy their DNA and sterilize the soil.
But a ground-breaking study published this year revealed this same radiation actually has the potential to feed life, under the right circumstances. Researchers at the Center for Astrophysics and Space Science at NYU Abu Dhabi, along with the Blue Marble Space Institute of Science and five other Universities, proved that certain microbial communities can live entirely underground and use radiation for energy.
Up to now, the search for extraterrestrials focused on traditional habitable planets, or "goldilocks zones", where the amount of water and sunlight provide energy for life to exist. But the new study, "Radiolysis as an Energy Source for Extraterrestrial Life", proves sunlight is not the only source of energy. Cosmic rays may kill life as we know it, but there may be alien life that use those deadly rays like a power charger.
The study introduces the idea of a Radiolytic Habitable Zone (RHZ). Instead of a habitable zone on the surface of a planet, the RHZ is subterranean. Cosmic rays hitting the surface create enough chemical energy to support life under the ground. How? Researchers show that ionizing radiation interacts with water molecules, producing solvated electrons (electrons trapped and stabilized in water, able to store and transfer energy). Solvated electrons can react with gases like CO₂ and CO to help make basic organic molecules, like acids, alcohols, and other building blocks of life. These building blocks can then be turned into sugars, amino acids, and small proteins.
Simply put, cosmic rays light up a chemical kitchen underground that turns carbon and nitrogen into food for alien life.
There are only three places in our solar system where this unique process could even happen. There needs to be the potential for underground water, and a lack of atmosphere so comic rays can do their thing. Two are icy moons - Europa (a moon of Jupiter), and Enceladus (which orbits Saturn).
Only one is a planet: our Earth-like neighbor, Mars. Despite its current desolate surface, evidence suggests subsurface water pockets exist there. Combined with the constant bombardment of cosmic radiation, Mars suddenly looks like an ideal habitat for this new form of life.
How can the researchers be so sure of this theory? They couldn't run tests on Mars. But they did use a robust combination of numerical modeling and theoretical calculations to demonstrate the RHZ was a viable idea. A big part of their method was the Galactic Cosmic Ray spectrum, the gold standard for modeling radiation's affects.
Oh, and there's one other thing that proves the RHZ can support life. It already happens on Earth.
The creature's called a Desulforudis audaxviator. And it's a remarkable single-celled microbe found deep underground -- we're talking nearly 2 miles deep -- beneath a South African gold mine. The animal survives in total darkness, with no access to photosynthesis for energy. Instead, just like the researchers proposed, the animal gets its energy from radioactive decay in the surrounding rocks. Incredibly, this creature is completely independent, handling all its life functions on its own, getting no help from any other organisms. It's a version of the RHZ happening right under our feet.
Indeed, this study opens the door to a world of life on Mars we'd never considered.
We talk about alien life so often, it seems like we've found it already. But the fact is, we've never actually come in contact with extraterrestrial organisms. And, while we've landed on Mars, no physical samples have ever been brought back to Earth.
But that's about to change. NASA's Perseverance Rover is collecting samples of Martian soil and storing them in sealed tubes. And over the next couple of decades, NASA is planning missions to collect those tubes and bring them back to Earth.
The tubes could contain groundbreaking insights into the planet's history.
We are now learning they could also contain our first contact with an alien.