Life on Mars

On the left is a tree chart showing the Earth life catagories (click for enlarged). If life was found on Mars, its biological makeup may or may not fit into this tree, it may even be a tree of its own. The search for life is in intricate part on NASA's current Mars mission structure for the next 20 years. All the way until about 2010, Mars Pathfinder type landers and rover will be sent to Mars. At about 2005 a sample return and life sensing technology demonstration mission will be sent to Mars. In 2007 based on the results from the last sample return mission, another sample return mission will be sent implementing the tested technologies used on the last. And until the first manned mission to Mars, these sample return missions will be used to implement NASA's current policy on life discovery. Which is, systematic search methodology will be implemented through remote sensing, surface sensing, and sample return.

Recently, a small rock found in Antarctica was identified as originating from Mars. This meteorite can be seen at different levels of magnification in the pictures below. Two possible source craters for the Martian meteorite ALH84001 have been identified through an extensive search of impact craters on Mars. Dr. Nadine Barlow, a planetary scientist at the University of Central Florida, identified the two likely source craters through a search of a crater catalog she compiled. Some characteristics of the meteorite helped Dr. Barlow narrow the search for possible source craters.

The 4.5 billion year old age of the meteorite indicated it must have come from the most ancient terrain on Mars. While the 16 million year old ejection age indicates that the crater from which the meteorite was ejected should still show very young features. Evidence of pre-ejection shock events indicates that one or more large, old craters should be found near the meteorite ejection site. Plus the presence of carbonates in the meteorite suggests that evidence of water should be present. Which then by having water present would be a great source to life.

But as the late Dr. Carl Sagan once said "Extraordinary claims require extraordinary evidence". Dr. Barlow's crater catalog, which contains information on 42,283 Martian impact craters, was used to search for fresh, elliptical impact craters larger than 10 km diameter and for fresh, circular craters larger than 100 km diameter on ancient terrain. The search produced 23 possible craters. The two craters which survived the analysis are both of the smaller, elliptical crater type. Being elliptical increases the probability of rock ejection because of the angle at which the impact occurs. Both are located in the heavily cratered southern highlands of Mars.

The first crater, located in the Sinus Sabaeus region of Mars south of the Schiaparelli impact basin, is 23 x 14.5 km in diameter. It displays a pristine ejecta blanket, a sharp crater rim, and is superposed on the rim of a much older, highly degraded, 50-km-diameter crater. Several small channels which formed early in the planet's history are located nearby, including one called Eros Vallis. The second possible source crater for ALH84001 is located east of the Hesperia Planitia region, is 11 x 9 km in diameter, and also displays a pristine ejecta blanket and sharp crater rim. It is located less than 10 km from an older 25-km diameter crater in an area which also shows some possible evidence of ancient fluid activity. The identification of possible source craters for ALH84001 will allow NASA to focus its efforts on these areas with future lander missions to Mars.