The possibility of life on Mars and other planets and moons has been debated for as long as we have known about those planets. Now that water has been found on the Mars, that possibility is more believable than ever. Sure, conditions are fierce on Mars, but research here on planet Earth reveals that life forms can be tough. In fact, wherever it was once thought that no life could exist, more and more organisms are being found that not only live, but thrive and evolve.
The boiling waters of Yellowstone National Park and other extreme thermal environments have species of thermophiles, or organisms that thrive in temperatures that would kill most living things. These thermophiles have specialized enzymes that keep their DNA from unraveling the way other life forms would. Chemicals from various thermophile species are used for a range of biochemical applications, such as DNA fingerprinting technology. Image by Flickr user v1ctory_1s_m1ne.
The Dead Sea has such a high saline content that pillars of salt form on its banks. Yet Halobacterium salinarum lives in its waters. Halobacterium is one of the most ancient of microbes, and depends more on light for survival than on oxygen. It adjusts its own needs according to the available light and oxygen. Image by Flickr user CharlesFred.
A copper mine in Montana was abandoned in 1983. As water filled the remaining hole known as the Berkeley Pit, minerals and metals leeched out and made it extremely acidic and poisonous. No fish or plants survived in the toxic water. It was thought to be completely dead until 1995 when a scientist recovered a slime that contained Euglena mutabilis, This protozoan manipulated its immediate environment to make it more livable! Researchers eventually found over 160 different species of microorganisms in the polluted water, some of which are being studied for use in cancer treatment. There is hope that Euglena mutabilis will eventually clean up the toxic water. Image by Linda Amaral Zettler and David Patterson.
Sinkholes deep beneath the Great Lakes have a very different chemical makeup from the water above. These pockets are filled with salt, acid, and sulfur, but have purple cyanobacteria that use sulfur instead of oxygen for photosynthesis. Other species that live too deep for sunlight to penetrate live on sulfur without photosynthesis.
In the depths of the Pacific ocean, volcanic vents support life too far down to take advantage of any sunlight at all. Tubeworms and giant clams thrive in volcanic environments by feeding on smaller species that survive only on chemicals without the advantage of photosynthesis. Image credit: NOAA.
The Socompa volcano is 20,000 feet high in the Andes mountains. Conditions there include little oxygen, lack of water, ultraviolet radiation, and methane. But scientists have found moss, algae, and over a hundred species of bacteria living in the shadow of Socompa. The area has been compared to Mars in its ability to sustain life.
Bacteria even live in the clouds! These microbes act as particles that ice form around and fall as snow or rain. They are called biological ice nucleators. Nucleators are found in plants and soil and are thought to ride on pollen as it is blown into the atmosphere. The part of the bacterial life cycle spent on vegetation may sustain an ice nucleator during its ride in the clouds, and the cloud seeding may be a mechanism for spreading it to distant parts of the earth.
No look at extremophiles would be complete without tardigrades, or water bears. These tiny animals are found in various extreme conditions on earth. They can survive hot and cold temperatures, radiation, lack of food and water, and even in a vacuum. The European Space Agency sent tardigrades into orbit in 2008, where they were exposed to cosmic radiation, solar radiation, and vacuum pressure. The space tardigrades were in a dormant state during the flight, which means their metabolism was slowed down considerably -a method they use to weather extreme conditions on earth. After returning from their adventure, they lived and even reproduced! Image by Flickr user Goldstein lab - tardigrades.
Two miles beneath the ice of Vostok Research Station in Antarctica, a huge freshwater lake has been isolated from the rest of the world for millions of years. The water is below freezing temperature, but stays liquid because of the pressure from the ice above. Researchers have not yet broken through to the water, but samples of ice just above the lake reveal the presence of microbe fossils. The lake is saturated with oxygen due to the temperature and pressure, and has been compared with the environments of Jupiter's moon Europa and Saturn's moon Enceladus. There are plans to send down a probe called a cryobot, but extreme care will be taken to preserve the pristine conditions of the isolated lake.