It’s a barren landscape. A frozen valley surrounded by craggy mounds, with a smattering of ice layering the frozen, rocky ground. At around 1,700 m above sea level, Antarctica’s University Valley has a mean temperature of -23 C. Here, the ice in the permafrost originates from vapor deposition rather than liquid water. And it’s here that NASA and McGill Univ. researchers are exploring the limits of life on Earth, and what microbial life might be like on Mars.
University Valley “is one of the coldest, driest places on Earth, and what makes it really exceptional is that there is no liquid water,” said Prof. Lyle Whyte, a cryo-microbiology specialist at McGill Univ., in an interview with R&D Magazine. “We don’t think there’s been liquid water at all” in the last 150,000 years.
The harsh conditions make the soil an alluring analog for Martian soil. Located in the McMurdo Dry Valleys, University Valley most likely resembles the northerly Martian site, where the Phoenix spacecraft touched down in 2008, about 5 million years ago. Back then, Mars was tilted and the northern landing site was situated towards the equator, where it was warmer, according to Whyte.
But after Whyte’s colleagues returned from Antarctica, a slew of tests revealed that the barren landscape may be even more barren than previously hypothesized.
The tests all point towards two things. That the soil and permafrost samples from University Valley contain an extremely low microbial biomass, and that microbial activity was undetectable in region’s ambient conditions.
“It’s not completely dead, but it’s almost dead,” he said, noting that the area approaches the “threshold on the limits of life.”
Prior to the discovery, Whyte and colleagues believed a functioning and viable microbial ecosystem would call University Valley home. His previous research into microbial ecosystems in the Canadian High Arctic’s Ellesmere Island revealed thriving ecosystems, with Whyte successfully isolating around 10,000 microorganisms.
“Here, we tried for two years and we managed to get six (microorganism) to grow on petri dishes,” he said. “Then, of course, the question becomes why.”
Collected in summer 2013 by a research team including Whyte’s student Jackie Goordial, the permafrost samples were obtained by drilling boreholes that reached depths between 42 and 55 cm. The team tested the IceBite auger, which was designed with Martian permafrost in mind. During the trip, the average temperature was -14 C, and never climbed above freezing.
While in the field, the team didn’t detect any soil respiration or methane flux, which would have been indicative of microbial life.
Upon return, testing continued in the lab, leading to the six organisms isolated by Goordial.
“We’ve taken those six organisms…and sequenced the genome of two of them,” Whyte said. “We think these organisms were deposited there, but that the environment is just too extreme that eventually they all just die off.”
The findings indicates that it’s unlikely there are microbes on or near the Martian surface, which is much harsher than University Valley.
But “this does not mean that there is no microbial life on Mars,” Whyte added.
Goordial and Whyte published their research in The ISME Journal.