COLORADO SPRINGS, Colo. -- In the Mars Exploration Rover (MER) landing site sweepstakes, the winners are: Meridiani Planum and Gusev crater.
NASA has concluded that these two touchdown zones on Mars offer the greatest science reward for the soon-to-be launched dual Mars Exploration Rovers.
Each MER robot will examine its landing site for geological evidence of past liquid water activity and past environmental conditions hospitable to life.
Calling the shots
Picking the two top sites follows a complex process of culling through some 155 prospective landing spots. The two sites are a giant crater that appears to have once held a lake, while the other is a broad outcropping of a mineral that usually forms in the presence of liquid water.
"Landing on Mars is very difficult, and it's harder on some parts of the planet than others," said Ed Weiler, NASA associate administrator for space science in Washington, D.C. It was Weiler who called the shots -- as to where each of the robots would be targeted.
"In choosing where to go, we need to balance science value with engineering safety considerations at the landing sites. The sites we have chosen provide such balance," Weiler said in a NASA press release.
Longstanding leader
A longstanding leader of the pack of possible landing spots has been Terra Meridiani. This area is believed to contain a rich deposit of hematite. Here on Earth, hematite can collect in hot springs or in standing pools of water. This grayish mineral on Mars is thought to be indicative of ancient hot springs.
"We have come amazingly far since Fall of 2000 when the plans for this effort unfolded," said James Garvin, NASA Mars Program Scientist.
"Over the past 2-plus years, we have engaged the broadest possible cross-section of the science community in a crusade to identify the most scientifically compelling, as well as science safe, landing sites for the MER rovers that are humanly possible," Garvin told SPACE.com .
Eyes wide open
Garvin said that todays announcement follows four landing site workshops. In addition, many human-years of effort have been put forth to understand the performance specifications of the MER landing system. That is, the difficult task of entry, descent, and landing followed by airbag roll stop, with each rover then wheeling away to begin their exploration.
"There has clearly been more diligent effort applied to optimizing science against the risks of landing on Mars for the sites under consideration than ever before," Garvin said in pre-landing site decision remarks.
"It is striking now, in retrospect, how little we had to go on for Viking and even Pathfinder. For MER, we are going to land with our eyes wide open thanks to the rich legacy of new data from Mars Global Surveyor and Mars Odyssey, as well as the greater fidelity of simulation models of the MER landing system," Garvin said.
On schedule
The first rover, scheduled for launch May 30, will be targeted to land at Gusev Crater. The second, scheduled to rocket Marsward on June 25, will be
precision-pointed to land at Meridiani Planum.
Which rover is targeted to a specific site is still considered tentative, while further analyses and simulations are conducted. NASA can change the order as late as approximately one month after the launch of the first rover.
The first mission will parachute to an airbag-cushioned landing on January 4, 2004, and the second on January 25, 2004.
Once they reach their landing sites, each rover's prime mission will last at least 90 Martian days (92 Earth days). The rovers are solar-powered, and in approximately 90 days, dust slowly accumulating on their solar arrays likely will decrease rover power, bringing to a close each robots sojourn.
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