When the Eyjafjallajokull volcano erupted in April, 2010, it caused some problems. An enormous ash cloud spread over Europe, prompting 20 countries to close their air space, stranding 10 million travelers, and causing an estimated $1.7 billion loss for the airline industry and untold collateral damage in sectors dependent upon timely transportation.
By the time the ash had settled, it was the largest interruption of air travel since World War II.
Despite the disruption, Charles Cockell saw an opportunity. The volcano spewed tons of ash that wreaked havoc on Europe, true, but it also generated fresh lava, a promising sampling opportunity for the University of Edinburgh astrobiologist.
Cockell studies life in extreme environments, investigating exotic sites to learn how organisms might eke out a living amid the most improbable conditions. Having spent years in pursuit of life’s limits, Cockell has developed a framework of biological possibilities, dividing the universe into three categories: uninhabitable locations, habitable sites that are not inhabited, and habitable substrates that do possess biological material.
On a planet sopping with life, astrobiologists lack access to one of these categories: uninhabited habitable environments. “Vacant habitats are extremely rare or transitory on Earth,” Cockell explained during a remote presentation to the Present-Day Habitability of Mars Conference, citing two contributing factors. The photosynthetic biosphere on Earth makes a lot of organic carbon and a lot of oxygen, and as Cockell explains, “these two products contaminate almost any habitat, providing a redox couple for aerobic respiration.” Combine this pervasive fuel with hydrologic and atmospheric conduits that facilitate rapid global connectivity, and every site that could be colonized by microbes is.
Which is why Eyjafjallajokull’s eruption got Cockell excited: the lava represented a rare case of a microbial habitat that had yet to be colonized. His research team hopped the next available flight to Iceland, racing against time and the inevitable spread of microbes to track the colonization process in real time.
But by the time they got their instruments in place, in June, 2010, the bugs had already moved in. “These lava flows are habitable,” Cockell explained, “and were inhabited by microbes on the surface within two months after the eruption.”
Unwilling to wait for another natural experiment to run its course, Cockell took matters into his own hands, realizing that an uninhabited habitat could be created artificially with a little digging. After finding a hydrothermally active site on the island (“if you stand there too long, your boots begin to melt,” Cockell reported), the scientists brought a subsurface rock to the surface. And there, before their very eyes, “the rock cools off quickly and then becomes suitable for life; it becomes an uninhabited habitat.”
Among the earliest microbial colonists were iron oxidizing microbes and other species capable of eating their host rock.
Cockell believes that the key ingredients for life were or are present on Mars, but that doesn’t necessarily mean there’s anything crawling around. For one thing, biology may have never reached or formed on Mars in the first place. Even if it did, if the mixing mechanisms were less efficient than on Earth – if life in one environment didn’t essentially mean it would be found in all similar environments – then habitable sites could have gone uninhabited for a very, very long time.
“It’s not part of our ecological thinking on Earth because they’re so rare,” Cockell reasons, “but uninhabited habitats might constitute significant portions of habitable spaces. Habitability is decoupled from the presence of life.”
