We humans like to think we’re pretty tough, able, thanks to our technology, to live in the most severe habitats on Earth.
But the fact is, there are other forms of life on Earth that have us beat hands down. They not only live all the places we live, they live in searingly hot water and absolute darkness near deep-sea ocean vents, in caves dripping with sulfuric acid, or, as researchers recently discovered, in the soil of one of the coldest and driest places on Earth, the McMurdo Dry Valleys in Antarctica–and the fact that they can live in such extreme places makes it more likely we’ll find life on Mars or other places in our solar system.
The Antarctica researchers, which included Dr. William Mahaney from York University in Toronto, weren’t surprised to find microbes–that’s what they were looking for. But they were very surprised to find them where they did, and the kind they did.
Microorganisms have been found in extreme environments in Antarctica before. Colonies of bacteria have been found thriving in water pockets embedded deep in solid ice, and living a few millimeters beneath the surface in rocks and soil, where they benefit from solar heating.
That’s where Dr. Mahaney’s team expected to find the most microorganisms this time, too; besides being warmer, the higher-up layers of soil have more iron, which microbes require. Further down in the soil there’s a very high concentration of salt, which researchers though would mean fewer organisms. Instead, they found more organisms in the deeper, salty layers than higher up, living in water with salt concentrations of up to 3,000 parts per million–“like Vodka” is how Dr. Mahaney put it.
Oddly enough, what sounds like it should be a lethal concentration of salt may actually be what allows the microorganisms to survive. Salty water freezes at a lower temperature than fresh water, and this water is so salty it doesn’t freeze until the temperature reaches minus 56.
The researchers have no idea how long the colonies of fungi and bacteria have been growing in the Dry Valleys; they could have been there for centuries, or even millennia. That’s astonishing because the fungi in question are Beauveria bassiana–which thrive on insects. But there are no insects in the Antarctic soil, raising the obvious question, “What do these colonies live on?”
Interestingly, just before the announcement of the Antarctic discovery, another research team announced the discovery of an entirely different type of “extremophile,” as organisms that live in extreme environments are dubbed.
These microbes were found 200 metres underground in Lidy Hot Springs in Idaho. All living things require energy to live, and most draw it from the sun, either directly (via photosynthesis) or indirectly (by consuming organic matter, which ultimately leads back to photosynthesis). But the Idaho microbes live in water devoid of measurable organic matter. Instead of drawing on the sun either directly or indirectly, the microbes, called Archaea, get their energy by combining hydrogen with carbon dioxide, and excrete methane. This may actually have been the first kind of metabolism that evolved on Earth.
The discovery in Antarctica and the one in Idaho both point to possibilities of life elsewhere in the solar system. In the case of Antarctica, the McMurdo Dry Valleys are as close to Mars in terms of terrain and climate as anywhere on Earth–and yet, they support life. In the case of Idaho, the fact that life can live in water devoid of organic material, in total darkness, bodes well because any water that still exists on Mars or on places like Jupiter’s moon Europa is similarly locked in darkness and presumably devoid of organic material.
Future robotic Mars probes will continue the search for life on the Red Planet, but some researchers believe it will finally take a human expedition to settle the question once and for all.
In H. G. Wells’s The War of the Worlds the Martians invade Earth but are defeated by Earth’s microorganisms. It would be ironic if it turns out that the real Martians are microorganisms–and microorganisms not that different from the ones that already call the more extreme corners of our world home.
