[meteorite-list] Mars Rover Landing Site Sweet Spots Not So Sweet

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:02:29 2004
Message-ID: <200203151630.IAA10600_at_zagami.jpl.nasa.gov>

http://www.space.com/scienceastronomy/solarsystem/mars_landing_sites_020315.html

Mars Rover Landing Site Sweet Spots Not So Sweet
By Leonard David
space.com
15 March 2002
              
HOUSTON, TEXAS - Finding safe and sound landing sites for two Mars
Exploration Rovers has proven difficult.

Scientists have been on the lookout for the best "sweet spots" on the
red planet. Wanted are places that yield top-notch science, yet are
touchdown friendly to the rovers. That gives each robot the best chance
for a lengthy tour-of-duty.

The pressure is on as the countdown clock ticks away for hurling the
twin rovers toward Mars next year.

A handful of Mars Exploration Rover (MER) landing zones has been
picked. They were "down selected", as NASA calls it, singled out from
some 185 locations. These high priority sites are being mapped by Mars
orbiting spacecraft and evaluated for science potential and safety
before final selection of two areas in May of this year.

But new data gleaned by both the venerable Mars Global Surveyor and the
newly arrived Mars Odyssey show the top candidate sites each to have
unique problems.

Details of various MER sites were presented here throughout the week
during the 33rd Lunar and Planetary Science Conference sponsored by
NASA and the Lunar and Planetary Institute.

Pinning down terrain

Attention is being paid to several Mars locations: Melas Chasma, Isidis
Planitia, Gusev crater, and the Sinus Meridiani Hematite Region.

Within each area, large landing ellipses have been divined, places
where a rover cushioned in airbags can bounce, then come to a full stop
and rev up science work. It's been a long game of pinning down terrain
that offers good science, but is non-threatening to the rovers.

"We know more about these four locations than any other places," said
Matt Golombek, Mars exploration program landing site scientist for the
Jet Propulsion Laboratory (JPL) in Pasadena, California. He is also
co-chair of the Landing Site Steering Committee.

Golombek said the Mars Global Surveyor's camera has snapped special
images of each potential MER landing spot, and several backup sites.
"We actually have geologic maps of the landing sites based on this
incredible data set," he told SPACE.com.

Those maps will also prove useful in determining the whereabouts of
each rover once down on Mars' surface. Furthermore, carefully
orchestrated treks by the mobile rovers can be scripted using the maps.

Cold hematite: hot and bothered

Golombek said each of the four candidate landing zones have problems to
some extent.

The most favored MER site is the hematite region, a place that shows
evidence for processes involving water.

"The hematite site, which has looked like the perfect landing site, has
finally fallen true to the salvo that there is no perfect landing site.
There never is," Golombek said. On one hand, the area appears smooth,
flat, and safe. From a landing point of view, that's nothing but good
news.

But the site may be too cold, reducing the longevity of the rover,
Golombek said. "It's not a concern for landing - but a concern
afterwards. But we don't know if that is the case," he said.

Work is now ongoing to better characterize the hematite site. Mars
Odyssey's sensors are expected to help certify the temperature profile
of that area, Golombek said.

Dust devil tracks

As for the other sites, Gusev crater has been recently imaged too. It
has been found to contain "dust devil" tracks. These ground traces are
produced by whirlwinds, a telltale sign that means there's significant
dust in that location.

"Dust can shorten the mission by getting on your solar panels. But
also, scientifically, if there's enough dust it covers up things. So
when you look around, you won't know what materials to go look at in
detail because everything will look like this dust layer. So that's not
good," Golombek said.

Melas Chasma is a spectacular site. Exploring it with a rover could
help determine whether water-deposited sediments are located there.

But being at a bottom of a canyon, Golombek said, winds could play
havoc with the spacecraft during parachute and airbag deployment
sequences. Also, the mesas associated with Melas Chasma are slightly
rougher than other landing sites.

Lastly, Isidis contains a worrisome field of rocks. "That's a real
concern," Golombek said. Sharp rocks, small and large, can knife the
MER landing airbags. Damage to the protective cushion of airbags during
a rover landing could ruin your day.

Hard looks at soft touchdowns

Later this month, Mars scientists and space engineers are meeting in
Pasadena, California to take another hard look at potential MER landing
spots.

Ultimately, the selection of touchdown areas is a balancing act between
"science wants" and "engineering needs" - a friendly but sometimes
testy tension.

"A site can be too rocky - or not have enough rocks," Golombek said.

Meanwhile, at JPL, the Mars Exploration Rovers are being assembled and
tested. Spacecraft engineers are getting a better handle on how the MER
robots best operate. That will feed back into determining where on Mars
the robotic right stuff can do its stuff.

"It's an evolving process. You never get done beating yourself up,"
Golombek said. "We want to go to two different places. Doing that we'll
get more diversity of what's really there on Mars," he said.

"You obviously want the rovers to be safe. You don't want to take
chances with hundreds of millions of dollars worth of spacecraft. On
the other hand, you want to address compelling science. And that's the
nature of the landing site process," Golombek said.
Received on Fri 15 Mar 2002 11:30:30 AM PST