The main purpose of the NASA rover Curiosity’s mission on Mars is to determine whether the Red Planet ever had an environment conducive to microbial life and to find the chemical building blocks of life. The spot that was chosen for Curiosity’s landing, the 3.8 billion year old Gale Crater, is situated near the planet’s equator. It is an area rich in minerals that form in the presence of water and Curiosity is searching for conditions that could be conducive to extremophile lifeforms.
So whereabouts on Earth would you find an environment similar to ancient Mars? The Dry Valleys of Antarctica are considered by many to have the most Mars-like conditions of anywhere on Earth. Researchers have found diverse life forms dating back nearly a hundred thousand years in subglacial lake sediments in Antarctica and have discovered microbial life within the frozen brine of Lake Vida, also in Antarctica.
Another location on Earth that could indicate what type of life there could be on Mars is Chile’s Atacama Desert. The Desert has been one of the driest, most inhospitable places on Earth for the last twenty million years. But researchers from Spain's Centre of Astrobiology and Chile's Catholic University of the North have discovered microbes even in this unforgiving terrain, more than 1.8 metres below the surface of Atacama's hypersaline substrates. The bacteria and archaea microorganisms survive on salt and moisture trapped by the formations; they thrive without any oxygen or sunlight.
The researchers used SOLID (Signs of Life Detector), which uses a biochip loaded with up to 450 antibodies which can be used to identify varieties of biological material, including DNA and sugars. The microorganisms have been found developing in a habitat rich in halite and other highly hygroscopic compounds (anhydrite and perchlorate) that absorb water. Saline deposits are known to exist on Mars so it is not a huge leap to think that hypersaline environments may also exist underground there. One of the impediments to potential Martian life is that of the low temperature; this would not be a problem if the substrates are of sufficiently high saline content as the freezing point of water then lower to -20 degrees Celsius.