The discovery of micro-organisms that can thrive in harsh environments without the need for oxygen or sunlight throws a new perspective on the search for extraterrestrial life

Where would you put a living colony of micro-organisms if you wanted to kill it? Probably in a place where there is no light and no oxygen, throw in some harsh temperatures for good measure and chances are that when you look again in a few million years, there will be absolutely no sign of life.

Nature does not work that way, and life is not so easy to eliminate — especially when it comes to microbial organisms, which have proven time and time again that they are very good at adapting to harsh conditions. Boiling water is so acidic that it can eat through metal, but even on the driest places on earth, typical living conditions for some species of micro-organisms that have been discovered by scientists over the years. The Deinococcus radiodurans bacteria for example, also referred to as ‘Conan the bacterium,’ for its impressive hardiness, can survive despite severe drought conditions, lack of nutrients or even radiation in excess of a million radiations — nearly a thousand times the amount that can result in immediate death of a human.

A team of scientists from the National Science Foundation headed by Dr Jill Mikucki has found another such species — adapted to thriving with no access to oxygen, sunlight or any outside nutrients. Published in the academic journal Science, a study by the team explains how a community of micro-organisms has managed to survive in a saltwater lake buried 400m deep inside the Taylor Glacier, Antarctica. For close to two million years, the micro-organisms have survived in an underground brine lake, cut off from any of the things we consider essential to biological life.

The underground lake, which is too salty to freeze despite frigid temperatures, occasionally oozes out of the side of the glacier. The result is an iron oxide stained outflow of saltwater named Blood Falls, which stains the blue-white landscape of the glacier.

Dr Mikucki and her team had discovered traces of microbial activity during earlier work conducted at Blood Falls and since then, they have been studying how the organisms survive in such an isolated environment. Analysis of the outflow from Blood Falls revealed that the lake contained no oxygen, yet 17 different species of micro-organisms were detected.

“When I started running chemical analysis [on the water], there was no oxygen,” says Dr Mikucki. “How were they able to persist below hundreds of metres of ice and live in permanently cold and dark conditions over millions of years?”

One hint came from the DNA of the microbes, which revealed them to be related to other known species of micro-organisms that use sulphate instead of oxygen for respiration. Further investigation revealed that the sulphate had been modified slightly in structure, hinting at its use in some sort of catalytic reaction. In addition, the water contains large amounts of soluble ferrous iron, which is what gives Blood Falls its unique red tint.

All of this led to the realisation that these micro-organisms survive by reducing insoluble ferric iron to soluble ferrous iron with the help of sulphate as a catalyst; the process can be described as the ‘breathing’ in and breaking down of iron in order to metabolise organic matter that has been trapped with it. Although this kind of metabolic cycle has been proved possible in lab experiments, this is the first time it has been seen in nature.

In addition to microbiologists, this finding has excited the community of scientists in search of life on other planets in the universe. The discovery of micro-organisms that can thrive in harsh environments without the need for oxygen or sunlight throws a new perspective on the search for extraterrestrial life and the belief that other planets are too inhospitable for living organisms. “A place like this,” says Slawek Tulaczyk, a glaciologist at the University of California, “would be probably as close of an analogue as we can find on this planet for subpermafrost life habitats on Mars.”

The red planet has always been the top candidate — at least in our solar system — for containing some form of alien life on account of some factors, like the existence of water, its distance from the sun and mineral analysis of the surface. Although the most recent robotic explorer, the Phoenix, did not detect any microbes, the discovery of ice and now the discovery of the organisms at Blood Falls have rekindled the hopes for Martian organisms being discovered.

Another, perhaps more likely, extraterrestrial habitat for the development or at least the sustainability of organic life is Europa, one of the largest of Jupiter’s 62 moons. Europa is about the size of our own moon, and is thought to have an iron core, rocky mantle, a saltwater ocean and an atmosphere rich with oxygen, much like the earth. However, unlike our home planet, Europa’s ocean covers the whole planet and its surface is completely frozen. Sounds like a very likely habitat for micro-organisms — at least, if Jovian organisms are as hardy as our own, given that they exist.

Arthur C. Clarke, in his novel 3001: The Final Odyssey wrote about life-forms that live near geothermal vents deep inside the Europan ocean and use sulphur for metabolism. We know of micro-organisms that thrive near geothermal vents deep under water here on earth – could similar organisms have developed on Europa?

Perhaps it is too quick to jump to conclusions, but the search for extraterrestrial life goes on. Europa is just one in an effectively infinite sea of possibilities — if just one solar system, as small as ours, can house three different planets suitable for the development of life, how many more such planets must there be in the tens of billions of galaxies in the entire universe!

Even if any aliens we discover are not advanced creatures that can teach us their ways and are only microbial, their mere existence would mean advanced forms of life are at least possible; and given the size of the universe, very likely.

The question remains: is there life on other planets? Can there be? Sadly enough, that question might never be answered — for me to dream that it be answered in my lifetime is hoping against hope, too. But the discovery at Blood Falls shows us how life perseveres in the harshest conditions. When faced with tough conditions, life adapts, organisms modify their lifestyles to adjust to the new conditions. At the very least, the discovery at Blood Falls gives scientists another shred of evidence for the remarkable resilience of life on earth, and offers us insight and hope into the possibility of extraterrestrial life.