Scientists are studying organisms from a lake atop a tall volcano to understand how life might have begun and survived on the planet Mars long ago. Studying martian analogs on Earth.
The surface of Mars is cold and dry — and because of Mars’ thin atmosphere, it’s bathed in high levels of ultraviolet radiation.
But Mars might have been wetter billions of years ago. Scientists wonder if life ever got started there –and if life still holds on below the martian surface. Nathalie Cabrol is an astrobiologist at the Ames Research Center in Mountain View, California. Last November, she led an expedition to the highest lake on Earth — in a crater on top of the Licancabur volcano between Chile and Bolivia. Six kilometers — or 20,000 feet — up, the thin atmosphere lets in a lot of harmful ultraviolet light. Ice coats the lake in winter.
Nathalie Cabrol: When you look at this picture of this environment, you see probably one of the best analogs to ancient martian lakes about 3.5 billion years ago. And when you are looking in the water, you see life is there, and it’s thriving.
Cabrol says that seeing these microbial life forms in the lake is encouraging.
Nathalie Cabrol: Because if we can find life there, that gives us some hope that life in similar conditions could have appeared and survived on Mars.
For two billion years on Earth, life had to appear, evolve, and survive in an enviornment bombarded by UV light. Understanding the survival strategies of the tiny plants and animals in the lake may explain how life survived a lake on ancient Mars.
The expedition team collected samples of the tiny, mostly microscopic, animals and plants in the lake and have taken them back to the lab to determine how they survive the UV bombardment.
Going to Licancabur was a huge challenge for the expedition. Temperatures were in the teens during the day, and at night plummeted to 40 below.
Dr. Cabrol describes the excitement of reaching the summit:
“After such an ascent, we were pretty excited about the lake. When we arrived, we had to walk a little bit on the flat at the summit to see the crater. And I rushed to the crater to see what it looked like, and what were the conditions. There was a terrible wind-chill at the summit that made the temperature very cold.
When I had my first vision of this lake that was a tremendous moment. The lake is emerald green lake — I was not expecting that at all. The color was sending us a message right away. Green is a very interesting color when you are looking for life! Basically it tells you that some organisms over there are playing with chlorophyll! So this was our first signal. ”
But the thing that struck me the most, was that despite the temperature at this altitude, it was completely liquid! There was not one trace of ice to be seen — anywhere. And that struck me. Because I was not expecting that at all, even though it is the middle of the spring going to summer, the lake is still very high, and I was just expecting to see some ice, and least some of it. And — nothing.
It was a very very striking moment. And then you have all the expectation and excitement because you say, “OK, all what I planned can be done!” It’s a fantastic moment. So we ran down, even though it was at 6000 meters, to reach teh lake shore. The second thing that struck me was the transparency of the water. It was crystalline. It tells you something — life is here, but it’s probably not overpopulated. And that’s interesting information because now it means there are very specialized living organisms — maybe only a specific species there. ‘”
Although the scientists expected to find life, they were surprised at its location.
Says Cabrol, “We knew that life was there. We knew that because of people hiking on top, people who like high mountaineering. Some went up there and saw things, so we knew there was life. ”
If life is there, it had to develop some kind of mechanism, to cope with the UV radiation, but we didn’t know which one. One that was straightforward, is water. Water will start protecting you, from the UV bombardment, if you go deep enough. When you go below 1 meter, the UV radiation equivalent to sea level.
But what is most interesting is this year we sampled at very shallow depths, between zero meters and one meter where radiation is not stopped, and this is where we found life. We have been back since November. We are already getting results on the type of living organisms that are there, and we are studying them pretty intensely. ”
Looking for Mars-like environments on Earth makes good sense.
“It’s going to help me because when I know what is the environment, what type of life there is there, I will know exactly what kind of experiment and what kind of instrument and what kind of mission strategy I need to put together to go to Mars and have the best chance as possible to be in a position of identifying life if it ever appeared on Mars,” Dr. Cabrol said.
You need to understand what you are looking for, and where it is. Earth is our model, and we have pretty good extremes on earth that are good analogs, depending on what you are looking for. Some people want to understand better the evolution of permafrost, they go to regions where permafrost is. Some want to understand better life in hydrothermal systems, and they would go to Yellowstone, very acidic environments, etc. etc. Some people who want to go to Europa and seek life and habitats will go to Antarctica to study lake Vostok. And this is a kind of way of rehearsing our mission, here and now, and then give it the best shot. Going to space is expensive, so we want to give it the best shot possible. ”
Brian Grigsby is an educator who participated in the original Licancabur expedition.
In an email, Grigsby wrote, “The Licancabur volcano hosts the highest (5916 m) and one of the least explored lakes in the world. The lake combines low-oxygen and high-UV radiation environment and is ice-covered most of the year. However, its bottom water temperature remains above freezing year-round. Why? What conditions make life possible in this hostile environment? These conditions make Licancabur a unique analog to sites listed as high-priority for the search for life on Mars and Europa. A two-year reconnaissance will provide (1) critical astrobiological information about the limits of life in this unique extreme environment, (2) scientific clues about potential planetary analogs, and (3) elements to design science mission strategies for planetary exploration. Next steps include analysis of data, writing of scientific papers for peer review, and an expedition next year to gather more data and make conclusions.”