Much of the impetus for the early spacecraft exploration of Mars was the possibility that conditions there might allow life. The Viking landers , along with stereo cameras to image the Martian surface carried three experiments to address this, with ambiguous results. Were we too geocentric to ask the right chemical questions?
A meteorite found on the Antarctic ice cap has provoked recent excitement, through the discovery of possible traces of life on Mars about 3.6 billion years ago (reported in an article in the journal Science as well as a NASA press conference. This meteorite was launched from a crater like this in the southern hemisphere of Mars about 16 million years ago. It is notable for its globules, only about 0.25mm across, rich in calcium carbonate - a mineral deposited only under water. Among the most widely hailed results of this study were striking images (via electron microscopy) of what look like microfossils, appearing at the size found for small terrestrial nanobacteria. They take the form of tubes and more tubes, a whole swarm of germ-looking things , and what everybody calls the worm .
Further exploration of Mars include two spacecraft which reached Mars in 1997. The Mars Global Surveyor was launched in November, 1996, reaching Mars on September 11, 1997. This orbital mission carries a mapping camera, laser altimeter, and spectrometer to map the surface rock chemistry of Mars. It was followed (and passed on the way) by the Mars Pathfinder, (later the Carl Sagan Memorial Station) which landed with the aid of air bags and deployed a small rover called Sojourner to examine the immediate area (and test the technology of such small remote vehicles). The landing site is in a region with abundant evidence that liquid water once flowed.Some of the exploits of Sojourner are captured in brief time-lapse movies:
Mars Global Surveyor has continued to carry out detailed mapping of the planet, and has delivered extremely high-resolution images of small areas to enable more detailed interpretation of the surface.
After the loss of the Mars Climate Orbiter (due to an odd compounding of metric-English conversions and old-fashioned management shortcomings), the Mars Polar Lander is scheduled to reach the planet in early December 1999. This spacecraft carries, in addition, two surface penetrators which might be able to tell how much ice lies beneath the surface.
Last changes: 10/1999