Now, the surface of Mars is too cold, dry and contaminated with radiation for life to thrive there.
But 3.7 billion years ago, this rust-brown planet may have been populated by subterranean microbes that eventually wiped themselves out.
At least this is the conclusion of a recent study published in the scientific journal Nature Astronomy.
Resembling Earth
The scientists used so-called climate and soil models to examine the possibilities of living things on the red planet about four billion years ago – at a time when conditions in the atmosphere were similar there and here.
This friendlier environment, the researchers believe, may have fostered simple microbes that used hydrogen as an energy source and produced methane waste.
But instead of favoring further evolution as happened here on Earth, the microbes on Mars may have caused their own extinction before evolution progressed further.
Got colder
The cause, say the scientists, lies in the distance from the sun.
Mars is about 228 million kilometers from the Sun, and the planet therefore has a greater need for greenhouse gases such as hydrogen and carbon dioxide to maintain a livable climate.
But when the microbes on Mars absorbed the hydrogen, they also destroyed the layer of greenhouse air that kept the temperature up.
Eventually the surface became so cold that complex organisms could no longer thrive there.
Found traces of methane
The scientists’ model shows that the surface temperature on Mars may have dropped from 10-20 degrees Celsius to a freezing 57 degrees Celsius during this period, and this probably pushed the first organisms down to depths of up to one kilometer in the Earth’s crust, where temperatures were higher.
Spacecraft have previously found traces of methane in the thin atmosphere on Mars.
NASA’s six-wheeled Mars rover, Curosity, has also detected methane during its wind-blown Mars rover. However, scientists have yet to find traces of whether any of these ancient microbes survived.
