BOULDER, COLORADO -- Dual Mars robots now being prepped at the Kennedy Space Center for launch will soon have places to go. A decision as to where NASA's two Mars Exploration Rovers (MER) will touch down on the red planet is slated for next week.
The ultimate selection of landing zones for each of the twin rovers falls to Edward Weiler, NASA's Associate Administrator for Space Science. Briefings on four candidate spots are now scheduled for April 10 at NASA Headquarters in Washington, D.C. After the briefings, Weiler is expected to give his okay on the top two landing locales.
Two separate rover liftoffs are slated from Cape Canaveral, Florida in May-July, with each robot making a scheduled stop on Mars in January 2004.
Small spots, big targets
After a lengthy process of culling through some 155 landing sites, the leading four Mars targets are: Meridiani Planum; Gusev crater; Isidis; and Elysium.
"Never has so much data been applied to four small spots on Mars," said John Grant, co-chair of the Landing Site Steering Committee at the National Air and Space Museum's Center for Earth and Planetary studies. Viking, Mars Global Surveyor, and Mars Odyssey imagery have played critical roles in evaluating prospective landing targets, deemed not only good for science, but safe for landing, he said.
"Data can be your best friend...but also your biggest curse," Grant admitted. For example, some sites were given "the kiss of death" because of tough to get to and rough terrain, high winds, or simply not enough science output.
Grant spoke here April 3 at the University of Colorado's Center for Astrobiology.
Bouncing to a stop
Scientists and engineers have wrestled with each Mars location. Both sites decided upon must be safe for the robots to land upon, as well as drive across. Each of the rovers is outfitted with the Athena payload of science instruments.
"These are probably the best calibrated instruments flown to Mars," Grant said.
Safe descent onto Mars' surface for each of the robots makes use of a parachute system and small rocket firings, leading to inflation of a huge set of airbags. The robots will come to a stop after bouncing repeatedly across Mars.
"Given that safety requirements are met, then site selection is science driven," Grant said. "Lots of people wanted to go to places that just aren't safe," he said.
Hematite: safe and sound science
Leader of the pack of four "sweet spots" on Mars is Terra Meridiani, also known as the Hematite site. On Earth hematite can collect in hot springs or in standing pools of water. Similarly, the grayish mineral on Mars may be indicative of ancient hot springs.
Not only is Terra Meridiani seen as great for science. Due to the relatively smooth landscape there, the site is highly favored by engineers who want a safe and sound landing.
Gusev and Isidis show evidence for surface processes also involving water. These sites appear to be a great match with the overall science objectives of the rover missions. That is, to determine if water was present on Mars and whether there are conditions favorable to the preservation of evidence for ancient life.
The fourth site, Elysium, appears to contain ancient terrain, which may hold clues to Mars' early climate when conditions may have been wetter.
Windy wild card
While second on a scientific wish list for a MER landing, Gusev crater has been found to come with possible wind shear problems. That could prove tricky during a rover's landing approach. On the other hand, engineers have worked hard on a robust landing system that should be able to counter any high-altitude gusts.
For Gusev, "the wild card is the winds," said Grant.
Next week, NASA's Weiler will be presented the findings and recommendations from leading Mars scientists and rover engineers, followed by his decision on the two MER landing spots.
Whatever landing sites are ultimately picked, Grant said, "this is going to be so coolbut some are more cooler than others," he concluded.
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