 Jan. 3, 2005 A year ago on Monday, a small spacecraft named Spirit bounced to the surface of Mars to begin a dramatic quest to learn if life exists beyond Earth. The plot remains thick, the ending still unknown, but evidence painstakingly collected by NASA's two robotic geologists, Spirit and Opportunity, continue to peel away Mars' mysterious past. Opportunity celebrates its one-year anniversary on Mars on Jan. 24.
A truly stunning achievement. Remotely operating a pair of fragile solar powered vehicles on another planet for an entire year. If we didn't already have spacecraft exiting our solar system, this would seem to be a milestone by itself. Instead, this is just another notch in the star-studded Orion's belt of modern American spaceflight.
However, until the rovers bounced to the surface of Mars and began conducting mineralogical studies of rocks and soils, scientists had no chemical evidence of water's existence. Opportunity, which landed fortuitously in a small crater in an area known as Meridiani Planum, provided the first and so far strongest evidence of water. "When Opportunity landed, the vehicle came to rest in a small impact crater about 20 meters in diameter. And after opening up and unfolding, the rover took a picture of the inside of the impact crater, only eight meters away or so from the lander. You can see layered bedrock exposed and easily accessible to the rover. It was a really magical moment when we saw this picture," said rover lead scientist Steve Squyres with Cornell University.
Personal friends of mine helped develop the compact X-ray spectrometer mounted on these wee-wheeled wonders.
Upon closer inspection, the rover found hundreds of small spherical formations nicknamed "blueberries" by the science team laced with an iron-rich mineral that commonly forms only in the presence of water. Scientists concluded that at least part of Meridiani Planum was covered by a shallow, salty ocean. The rover also snapped pictures of a rock called "The Dells," etched with ancient ripples. "This was caused by water long ago, flowing over a bed of sand, and forming little ripples," said Squyres. "Then they got preserved for all time in the rock." Whether life had an opportunity to take hold while water was present will be a question for future missions to answer. NASA is preparing to launch in August its most sophisticated remote sensing device to date. It will be followed later this decade by rovers to dig deep into the frozen Martian ice and a science lab to analyze rock and soil samples for microbial life.
Scientists are far from finished with Spirit and Opportunity. The rovers, which were designed to last 90 days, are continuing to explore new vistas. Spirit, which was expected to travel about one-third of a mile, journeyed nearly 2 1/2 miles to reach the top of a group of hills named after the shuttle Columbia crew. The layered rocks hold promise of additional findings of past water. Opportunity has climbed out of a crater and is poised to investigate its own discarded airbags. Scientists want to study the soil that was uncovered by the rover's bounced landing, while engineers want to use the data to design better gear for more challenging landings.
All this mechanical performance in an environment, not just of sand or dust, but fines. Hovering in the one micron or less range (~ 1/1,000,000 Meter) this end product of a sustained non-aqueous environment usually jams the most robust mechanisms and can even cake up an object with no moving parts at all. Add a chemically reactive nature to such naturally-ocurring jeweler's rouge and you have the daily dose these rovers get.
My hat is off to NASA for this spectacular effort. In the absence of any moon program, this certainly serves as continuing evidence of American aerospace excellence. 
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