Earth's Most Mars-Like Environment

A region of Earth so barren and desolate that it's often compared to Mars is home to simple but thriving ecosystems, suggesting that life could indeed survive on the Red Planet.

"If you have just a few basic things," said University of Colorado at Boulder microbiologist Steven Schmidt, "you can get a complex ecosystem going, even in one of the harshest places on the planet."

Schmidt's team studied soil from the upper flanks of the Socompa volcano, high in the Andes mountains. Straddling Chile and Argentina, the volcano is surrounded by the Atacama desert, one of the few spots on Earth to contain regions devoid of any life form.

At 20,000 feet above sea level, the Socompa's upper flanks are especially harsh: there's little oxygen, and ultraviolet radiation passes easily through the thin atmosphere. But where steam from the volcano bursts through the ground, there's methane and water. Add that to atmospheric carbon dioxide, and conditions resemble what once existed — and may still exist — on Mars.

Scientists recently found that Mars still belches methane into its carbon-dioxide rich atmosphere. And though NASA's Mars Rover found water only in ice, rather than the liquid necessary for life as we know it, many geologists suspect water is present beneath the planet's surface, warmed by the Mars' still-hot core.

"The Socompa microbial ecosystem is an extremely exciting Earth analog for investing how life on Mars may survive in hydrothermal oases, where water, heat and nutrients are being provided from deep within," said California Institute of Technology biochemist Adrian Ponce, who was not involved in the study.Schmidt's team sampled soil around volcanic vents, and from regional soils thought to be lifeless. In the vent soil, they identified moss, algae and about 500 species of bacteria. Apart from the discovery of a new species of mite, said Schmidt, these findings are most significant for their level of genomic detail, since the organisms were already known to exist.

Far more surprising was the presence of roughly 100 species of bacteria in earth taken miles from volcano's vents. No life at all was thought to exist in that parched soil.

"That's the more Mars-like soil," said Schmidt. "There's definitely a microbial community there."

According to study co-author Elizabeth Costello, a University of Colorado at Boulder biologist, the bacteria "may stay in a dormant state until a snowfall occurs and water is provided to them."

This, she said, might occur "fairly rarely" — an understatement for a region in which years can pass between rainstorms.

"We have no idea what they're doing or how they're living," said Schmidt, who plans to further study the unlikely bugs.

Lisa Pratt, a NASA astrobiologist who was not involved in the study, mirrored Ponce's excitement, saying the Socompa vents "may be the best example yet of an Earth analogue for habitable surface and near-surface environments on Mars."

"If water, a carbon source and energy for metabolism are present, then life seems to manage daunting extremes," said Pratt.

That is, if it can get started. Some scientists question whether the chemistry on Mars has ever been conducive for life to begin, even if we know organisms can evolve to survive those same conditions.

But life didn't necessarily need to bootstrap itself on Mars: it could have arrived there on rocks knocked into space by an asteroid's collision with some other, more temperate planet.

Bacteria are, after all, able to withstand the vacuum of space and simulated meteorite impacts. Just as Earthly microbes likely drifted through the upper atmosphere onto the Socompa volcano, extraterrestrial microbes could have drifted to Mars.

"Certain microbes have spore forms that can survive in space," said Schmidt. "It's conceivable."