Habitability and Biology - page 3
Can Life Exist on Mars Now?The recent discovery that ancient Mars probably had liquid water on its surface means that the conditions for life probably existed at some time in Martian history. But what about the present? Could there be life on Mars now?
If any life exists on Mars today, scientists believe it is most likely to be in pockets of liquid water beneath the Martian surface. These underground water chambers could harbor microscopic organisms called extremophiles, organisms that have evolved unique strategies for existing in extreme environments.
In Mars' Meridiani Planum, the Mars Exploration Rover Opportunity discovered hematite and jarosite, minerals that are typically found in hot springs and other acidic bodies of water, such as the Rio Tinto in Spain. If subsurface hot springs do indeed exist on Mars, then the microbes that thrive in these environments might also be found there.
Jarosite, a yellowish-brown mineral that usually develops when volcanic rocks are altered by water vapors, has been found on the surface of Mars. (Image credit: NASA)
In 2004, the Mars Express mission detected signs of methane in the Martian atmosphere, and some scientists believe that the methane could indicate the presence of extremophiles called methanogens - a form of microbial life that gives off methane as part of its metabolic processes.
On Earth, microbes have also been found thriving in extremely cold environments, such as beneath ice sheets in Antarctica. Since Mars is a cold planet with large ice deposits, it is possible that similar microbial organisms might be found there.
Hot springs, such as those of Grand Prismatic Spring in Yellowstone National Park, often harbor organisms called extremophiles, which can survive in environments considered too extreme by human standards. (Image credit: Laurie J. Schmidt)
What Might Phoenix Find?Phoenix will assess the habitability of the Martian polar environment by conducting sophisticated chemical experiments that will test the soil for life-giving elements such as carbon, nitrogen, phosphorus, and hydrogen.
But even if the Martian soil contains the right mix of ingredients to sustain life, it may also contain hazards that prevent biological growth, such as powerful oxidants that break apart organic molecules. These harmful oxidants are often found in dry environments that are bathed in ultraviolet light, such as the surface of Mars. But just a few inches below the surface, the soil could protect organisms from the harmful solar radiation.
The Phoenix robotics team at JPL performs some tests to determine the effectiveness of the scoop design to collect and deliver samples. (Image Credit: NASA/JPL)
Phoenix will land in the Martian arctic plains, where its Robotic Arm will dig through the dry soil to the ice layer. Samples of the soil and ice will then be brought to the Lander's platform and analyzed using special scientific instruments. These samples may hold the key to understanding whether the Martian arctic is a habitable environment.
One of the Phoenix science team's top priorities is making sure that any organic material collected is indeed Martian in origin - not hitchhiking microbes from Earth. To ensure the spacecraft is sterile upon launch, the most sensitive surfaces of Phoenix, such as the Thermal and Evolved Gas Analyzer (TEGA) and the robotic arm, are being built in Class 1000 clean rooms, where there are no more than 1000 organic particles larger than 5 one-millionths of a meter in any given cubic foot of air. After construction, these surfaces are treated by extreme heat for up to 100 hours, and then sealed in protective material that organic material cannot penetrate. Because Phoenix's science instruments are so sensitive to organic materials, the spacecraft's surfaces will actually be far "cleaner" than is required by NASA planetary protection standards.