In 1996 scientists discovered what looked like fossil remains of simple organisms in a Mars meteorite found in the Antarctic. This might indicate that life developed on Mars in the past. Where should we concentrate our efforts to find more evidence of life?
This recently discovered rock from Mars, meteorite ALH84001, leads scientists to hypothesize that life once existed on Mars. These scientists believe the structures in the rock have a biological origin. If there are organic remnants in the meteorite, it stands to reason that by returning to the site from which this rock came--or similar sites--samples with the same sort of organisms could be found. However, there is by no means a consensus on this issue, which must be understood as one presenting only claims of possible evidence.
Nadine Barlow, a scientist from the University of Central Florida, has found two impact sites on Mars that could be the birthplace of ALH84001. Returning there, however, would only give scientists the same sort of information they have already found here on Earth. To find more definitive evidence requires going to a site better suited for life, and fossil formation, than the plains in the ancient cratered terrain.
A dried lake bed would be one of the most promising sites. Lakes could have provided a comfortable spot for life to exist long after the conditions on dry land became uninhabitable. Sediments on the bottom of a lake bed would have been an excellent place to trap and preserve fossils.
Photo. This photograph was taken by the Mars Pathfinder probe, which landed on the Red Planet on the Fourth of July 1997. The Pathfinder landed in Ares Vallis, a dried flood basin chosen for its plentiful rocks. In the mission simulation, you will have the option of landing near this spot. Courtesy of NASA, JPL.
Besides lake beds, another great spot to search for life could be former hydrothermal springs. In these springs, hot water from deep within the planet rose to the surface and cooled quickly. Under these circumstances, the minerals within the hot water separated out as solids, preserving any life forms in the water as fossils. Hydrothermal springs could probably survive on Mars long after other liquid water habitats because they derive their energy from geothermal sources.
A third possibility is the polar ice caps. The intact remains of a Martian organism could still exist at either of these locations. Micro-organisms have been found in the the permafrost of Siberia, dormant but still alive after being frozen at 15 degrees F for more than 3.5 million years. The southern polar regions of Mars include areas that have remained at temperatures of -95 degrees F throughout the entire history of Mars. Because of the lower temperatures, micro-organisms would degrade at a much slower rate than in Siberia and could possibly still be found.
Photo. In this image, another transmitted to Earth from the Pathfinder probe, the Sojourner rover pulls up against a boulder dubbed "Yogi" with its x-ray spectrometer, an instrument used to test rocks for their chemical compositions. The options of a rover and of an x-ray spectrometer will both be offered to you in the mission simulation. Courtesy of NASA, JPL.
Is it worth the effort to return to Mars? Oh, yes. Discovering life on another planet would confirm that humans are not alone in the universe. And if life exists on two of the three worlds humans have explored--Earth, the Moon, and Mars--then it is likely that life is abundant in the universe. What a profound discovery we will have made! When do you launch your Mission to Mars? What scientific instruments should you take with you? What problems will you encounter? Where will you search? The choices are yours. Good luck, intrepid explorer!
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