Scientists working on NASA's Mars Exploration Rover (MER) Project have picked the top two "scientific sweet spots", the landing sites, for a set of soon-to-be-launched robotic spacecraft.
MER scientists met in closed-door sessions late last week at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California to thrash out the merits of a handful of landing locales.
Their final selections are part of an on-going decision making process of where best to send the twin Mars rovers. Scientific merit and landing safety are top factors that weigh-in big time.
Ultimately, the final verdict regarding MER set down spots is being made in April and rests on the shoulders of NASA's chief space scientist, Edward Weiler, in Washington, D.C.
For the past two years, however, Mars scientists have debated -- often in a rarified, super-hot atmosphere of their own making -- where to target the expensive robots. Over that time, they have brooded over some 185 potential landing spots.
Consensus building
And the winners are: Meridiani Planum and Gusev Crater.
There was near-unanimous agreement over those top two recommended sites, said Mark Adler, MER Landing Site Engineer at JPL.
"The science team recommendations are based on science only, and do not take into account safety. That comes in further downstream in the process," Adler told SPACE.com.
"The real goal for this workshop was to put together sets of scientific pros and cons for each site," said Steve Squyres, principal investigator at Cornell University for the Athena science gear that each rover is to carry. In addition, last week's gathering of experts hammered out a list of scientific hypotheses for each site that can be tested with the Athena payload and the MER rovers, he said.
"Lots of material was presented at the workshop and synthesized by the workshop participants. This material is what the Athena science team usedto come up with our final recommendations to the MER Project. It's also part of what will go to NASA Headquarters to help them make the final site selection," Squyres told SPACE.com.
Squyres said that his hope all along has been there would be a near-unanimous consensus of the team about what the top two landing sites should be. Also, that those sites picked would be consistent with the recommendations of the outside science community.
"I'm glad to say, we achieved that," Squyres said.
Landing zone science
What's so special about the two candidate science sites, Meridiani Planum and Gusev crater?
Often called the "hematite site", MER Project scientists are tagging that landing location by its proper name - Meridiani Planum, or just Meridiani. "Hematite is a mineral and a scientific hypothesis. Meridiani is a geographic place, Squyres noted.
Hematite here on Earth can collect in hot springs or in standing pools of water. Similarly, the grayish hematite on Mars may be indicative of ancient hot springs.
In the case of Gusev Crater, some scientists believe it is an ancient lakebed. One fascinating feature of Gusev is a large channel that enters it from the south - perhaps a source of water that produced a large lake within the crater.
Speculation has it that both landing zones may well carry clues as to past biology on Mars. Whether these sites hold promise as abodes for life today cannot be ruled out.
A tough choice pondered by scientists is what to do if a launch failure aces out one of the Mars robots. If faced with just one landing attempt, the voting preference was Meridiani Planum over Gusev Crater, Adler said.
The launch window for the first rover opens later this year, on May 30. Liftoff window for the second rover begins June 25. Touchdown of the first rover on Mars is January 4 of next year. The second wheeled robot would land on January 25.
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