On August 6, 1996, NASA made a startling announcement-- that a rock called "ALH84001," considered by many meteorite specialists to be a sample from Mars, contains features that some scientists suggest are indicators that Mars once had primitive life forms. At a press conference held on August 7th, the scientists led by Dr. David McKay of the Johnson Space Center outlined their evidence: organic molecules, microscopic mineral grains of magnetite, and pictures of tiny microscopic features that some people said "look like maggots." The press conference generated a lot of excitement. President Clinton said that Vice President Al Gore would convene a special Space Summit in November to look at what NASA should be doing to explore Mars in light of these findings. The entire Mars science and engineering community has been abuzz with talk about attempting to bring back samples from Mars using robotic spacecraft as early as 2001 or 2003.
Regardless of whether the latest findings about meteorite ALH84001 really are indicators of past life on Mars, this question has long intrigued Earth's people. Four and a half billion years ago, Mars and Earth were very different than they are today-- however, at that time, scientists suspect the two planets were very similar to each other. Does this mean that both planets could have had life on them, early in their history? To some, it seems possible.
In 1995, NASA outlined a strategy to search for evidence of life on Mars (see NASA SP-530, listed below). A key to this search is to look for the kinds of rocks and minerals that are known to contain microscopic fossils of the Earth's oldest life forms. Such rocks include evaporites (salts from dried up lakes), carbonates (e.g.-- limestones from dry seabeds), and any rocks that might form around hydrothermal vents (like the silica-rich rocks at the hot springs in Yellowstone National Park, U.S.A.).
The Mars Global Surveyor Thermal Emission Spectrometer (TES) is perfect for mapping out the types of minerals and rocks that occur on Mars. TES should be extremely helpful in the attempt to find favorable sites to look for fossils of ancient martian life!
White Rock is a bright, eroded feature on the floor of a martian crater at 8 S, 338 W. It is about 15 km (9 mi.) wide and up to 540 m (1,770 ft.) thick. Arizona State University alumni Dr. Steve Williams and Dr. Jim Zimbelman suggested in 1994 that it has a lot in common with dry lake beds in Earth's desert regions. They proposed that White Rock is composed of the salts that are left behind when a desert lake evaporates. Did a lake once fill the crater that White Rock is found in? NASA's strategy for looking for fossil life on Mars includes looking for the salts in ancient, dried-up lakes. The Mars Global Surveyor Thermal Emission Spectrometer (TES) is ideal for finding out whether places like White Rock are composed of salt minerals like "halite" and "gypsum."