In Chile’s Atacama Desert, Volcan Llullaillaco is Mars on Earth — or about as close to it as you can get. At 22,000 feet above sea level, it’s the second highest active volcano on Earth. Most of the mountain is a barren, red landscape of volcanic rock and dust, with thin, dry air, intense sunlight and winds that will blow your tent down the mountain.
While the ground can heat up to 90 degrees Fahrenheit, air temperatures rarely reach above freezing. When snow falls, it turns to gas just as it hits the earth. Occasionally, snow can collect in windblown banks, which then melt into icy spires up to 16 feet tall. The Spaniards called these “nieves penitentes,” penitent ones, because they look like hooded monks doing penance.
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These conditions high up on the volcano made it seem about as lifeless as Mars. But a team of researchers led by Steven K. Schmidt, a microbiologist at the University of Colorado Boulder who studies extreme life, have discovered microbes living in and around the penitentes at 17,300 feet above sea level, about one thousand feet above the point at which vegetation stops on Volcan Llullaillaco.
The scientists’ descriptions, published recently in the journal Arctic, Antarctic, and Alpine Research, exemplify how life on Earth consistently pushes our expected limits — and may even offer clues to how or where life could exist in similar environments elsewhere in the solar system.
Dr. Schmidt thought the volcano might be an ideal place to study the limits of life on Earth after he heard about three children unearthed there in 1999. The 500-year-old mummies were perfectly preserved without embalming agents.
The mummies when buried were “huge bags of microbes,” full of water. That they hadn’t decayed suggested the conditions deep beneath the volcano’s soil were constantly too cold and dry for any life to function.
But what about closer to the surface, where environmental conditions vary?
Dr. Schmidt knew microbes had been found in the surface tephra, or volcanic soil, of the same volcano, as well as a nearby one at slightly lower elevations. But little was known about the summits or penitentes.
By discovering what conditions supported patches of life among this mountain’s sterile heights, perhaps he could truly understand life’s limits.
In March 2016, the team hoped to collect soil samples from the summit of Llullaillaco. But after a week’s journey from the coast to the desert, poor weather pushed them to explore the volcano’s penitente fields instead. This was not the volcano’s most extreme environment, but it was still quite harsh and far higher up than where it seemed life could persist.
When someone on the expedition serendipitously noticed red snow at the base of some penitentes, they wondered if it could be watermelon snow, an algae found in other frigid environments.
Scientists think penitentes are the result of an unusual mix of conditions, involving wind, temperature fluctuations and the sun’s ultraviolet rays. As tiny indentations in snowpacks melt, penitentes grow up. This also liberates life’s vital elixir — liquid water.
Microscopic and genetic analysis confirmed the red patches at the bottom of the penitentes were snow algae. And the scientists also found cyanobacteria, yeast and even more complex microbes in the ice and shallow tephra downhill from where penitentes melted.
“We see the penitentes as an oasis in this harsh landscape,” said Dr. Schmidt, offering water and protection from the elements to wind-carried microbes that were likely dormant before the water reanimated them.
And because penitentes are also found in the Himalayas, Pamirs and Hindu Kush — as well as on Pluto and Europa — a closer look could point the way toward discovering lively oases on other worlds too.
“I am excited about this finding for its astrobiological implications,” Lynn Rothschild, an astrobiologist at Brown University who was not involved in the study, wrote in an email.
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