[meteorite-list] NASA Plans To Select Mars Rover Landing Site Soon (MSL)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 7 Jun 2011 07:48:10 -0700 (PDT)
Message-ID: <201106071448.p57EmAn8010073_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/news/n1106/05mslsites/

NASA plans to select Mars rover landing site soon
BY STEPHEN CLARK
SPACEFLIGHT NOW
June 5, 2011

PARIS -- NASA officials are in the final stages of deciding the
destination for the agency's Curiosity rover, a complex mobile science
laboratory scheduled to be shot toward Mars in November.

Scientists already whittled down a list of several dozen candidate
landing sites to four finalists, and now it's up to project managers and
top NASA officials to determine which of the landing sites Curiosity
will study.

The spacecraft is scheduled to launch Nov. 25 and reach Mars as early as
Aug. 6, 2012.

The four finalists: Eberswalde crater, Gale crater, Holden crater and
Mawrth Vallis.

Matt Golombek, co-chair of the landing site steering committee, said all
four locations hold great promise if Curiosity ends up there.

"In many cases, it boils down to people's preferences and not
necessarily that one site is better than another," Golombek said.
"They're all great places, but there's different science at different
sites. And deciding amongst those could be very difficult."

The final decision will come from Ed Weiler, NASA's associate
administrator for science in Washington. That's expected by the end of
July, according to multiple mission officials.

The selection will help engineers tweak the spacecraft's flight path
after it blasts off atop an Atlas 5 rocket. Theisinger said NASA
committed final trajectory information to the launch team by August.

The process of collating data, preparing presentations and forming a
recommendation has already started.

The Mars Science Laboratory project office could finalize their
recommended landing site in meetings this week, but then the decision
must be approved by managers at NASA's Jet Propulsion Laboratory in
California and ultimately by Weiler, according to Pete Theisinger, the
mission's project manager.

The rover's precision landing system allows engineers to carefully
target its landing site to avoid craters, large boulder fields and
mountains. High-resolution stereo imagery from NASA's Mars
Reconnaissance Orbiter satellite also provides detailed maps of each
landing site.

And unlike NASA's previous rover missions, Curiosity won't use airbags
to land. Earlier rovers dropped to the surface cushioned by inflated
airbags, bouncing and rolling to a stop up to a mile from the initial
touchdown point.

Curiosity's rocket-assisted touchdown will use a sky crane vehicle to
gently lower the rover to the surface on a bridle, so engineers don't
have to worry about sharp rocks or craters along a lengthy bounce path
away from the initial landing site.

Theisinger said all four candidate sites are equally safe in the view of
engineers.

"There are extremely modest differences between the sites from an
engineering standpoint, and none of those differences I think is
sufficient for us to say from an engineering standpoint you can't go to
one of them," Theisinger said.

Golombek, who also particpated in landing site decisions for previous
rovers, said engineering concerns helped guide the decision on those
missions. This time, he said, it's all about the science.

"What's happened in previous site selections is that the engineering
constraints have helped, if you will, the scientists make a decision
because there have been really clear places where things are safer,"
Golombek said.

Using high-resolution imagery and the latest spectroscopy data,
engineers plotted hazards at each location and developed potential drive
routes the rover would take to reach the most interesting scientific sites.

"We actually can see the rocks directly in those images and map them
out. We provide all that data to the engineers to determine how
difficult or slow it takes to drive in those different terrains,"
Golombek said.

According to Theisinger, the rover is targeting an ellipse measuring
about 25 kilometers by 20 kilomters, or about 15 miles by 12 miles.
Better navigation later this summer and actual trajectory projections
after launch could refine the ellipse size.

"The end result of all that work, and this is the first time this has
ever happened, is that it's very hard to distinguish any of the four
sites based on safety or trafficability," Golombek said. "That means it
boils down to science. The difficulty there is everybody likes different
kinds of science better. It's almost like religion."

All four sites show strong evidence that water once existed there,
potentially creating a habitable environment where ancient life could
have thrived. Scientists hope organic molecules may still be there today.

Two of the landing sites are on the southern hemisphere, one in the
northern hemisphere, and another is near the Martian equator.
 
Eberswalde is an ancient river delta including dried up stream channels
and strong signs of clay deposits, another indicator of the former
presence of water. Researchers believe the site's 40-mile-wide crater
was once filled with water being supplied by a river.

With two basins separated by a central high mound, Eberswalde harbors
tough driving conditions for Curiosity. But engineers say the rover
could handle it.

Holden, a crater spanning nearly 100 miles in diameter, is part of a
string of craters that look like they were once connected by a stream.
Scientists propose landing on a relatively flat plateau, then driving to
several nearby sites where exposed bedrock could hold clues about the
location's history.

The crater was probably once filled with water, and a catastrophic flood
may have emptied the lake more than 3 billion years ago.

Gale is another site once flowing with water. The crater's central mound
reaches more than 3 miles above the floor, and researchers want
Curiosity to touch down in a flat region just off the the mountain's
flank. Then the rover would start climbing the mound, pausing along the
way to study layers of clay, sulfur and oxygen-bearing minerals.

Engineers say the challenging drive isn't a problem for Curiosity.
Scientists already mapped out a sample traverse path climbing nearly a
mile in altitude up the mountain, and the scenery would spectacular,
Golombek said.

Mawrth Vallis, one of the oldest and broadest valleys on Mars, offers
one advantage over other sites. The rover would land directly on layered
rocks containing clay materials that may have formed in a watery
environment.

At the fifth landing site workshop held in May, scientists gathered for
the last time to digest the latest data on each site.

"The data dribbles in slowly," Golombek said. "It's our understanding
and interpretation that has changed. There were definitely some new
results that helped improve the cases of some of the sites and their
scientific desirability."

Now the decision is in the hands of NASA management.
Received on Tue 07 Jun 2011 10:48:10 AM PDT