Those
plucky robots--Spirit and Opportunity--are
continuing their respective missions on Mars, each wheeling toward new science
objectives.
Images
from Opportunity show an expanse of dunes at
Meridiani Planum. Rover operators are taking precautions that the golf
cart-sized robot won't get bogged down in any sand trap--to avoid a repeat
performance that halted movement of the machine last April.
It
took nearly five weeks for engineers to extricate Opportunity's
wheels that became buried in soft sand of a small martian
dune--later dubbed "Purgatory Dune" by the Mars Exploration Rover team.
On
the other side of Mars at Gusev Crater, Spirit continues to climb Husband Hill
within the Columbia Hills. Using its science-instrumented robot arm, the rover
has made observations that are causing a stir within the circle of Mars rover
scientists on the project.
In a maze
Opportunity
is pressing onward to Erebus crater, said Steve Squyres, lead science team
member for the Mars Exploration Rover effort at Cornell
University in Ithaca, New York.
In
a rover update, Squyres noted that driving the rover across the sandy landscape
is a challenge.
"We
are literally in a maze. The easiest going is to stay within the troughs
between the ripple crests, which run roughly north-south. So the best way to
make southward progress is to follow a trough until it peters out, make a 'lane
change' to a nearby trough, and continue onward," Squyres explained.
Using
imagery taken from Mars orbit, scientists and engineers see what they term the
"Erebus Highway".
It is a stretch of light-toned terrain, perhaps consisting of exposed bedrock.
If so, that'll make easier going for Opportunity.
"We
also like the idea of getting to bedrock from a science perspective," Squyres
added. "It's been a long time since we've looked at any rock with Opportunity."
Cross-country driving
But there's a catch, Squyres warned.
"The
entrance to the Erebus Highway
is not straight south of us, along the troughs. It is a bit off to the east, on
a heading closer to 160 degrees or so," Squyres
explained. However, to get there, the rover has to go "cross-country, going up
and over quite a few ripple crests."
"That's
do-able," said Squyres, "but it's also a lot slower
than just bombing straight south down a nice trough."
A
driving decision is forthcoming. Heading for the highway means making slow
progress for awhile, but perhaps a better route to Erebus Crater. If the rover
wheels down the troughs instead, it's a speedier path to Erebus Crater.
"So
it should work either way," Squyres said. "Whether or not we're actually going
to 'hit the Highway' is an open question at this point, but Erebus isn't too
far off either way you cut it."
There's
some other good news about what Opportunity is
driving through. The terrain appears to be changing as it moves south of
Purgatory Dune. Rover images show fewer tall dunes, more pebbles in the
troughs, and what might be tiny outcrops of bedrock.
"I
don't want to jump to conclusions," said Squyres, "but
the driving definitely looks a little nicer here than it did a hundred meters
back."
Chugging through
the data
The
Spirit robot at Gusev Crater is also on the move.
During
its ascent of Husband Hill within the Columbia Hills, the robot came across a "very
cool outcrop" of layered bedrock that has been tagged as Independence Rock,
Squyres said.
"We've
thoroughly worked it over with all of the arm instruments now, and it's very
strange stuff," Squyres reported. He said it was one of the oddest things seen
at Gusev.
"I'm
not ready to go into much detail here about the chemistry and mineralogy yet,
since we're still chugging through the data," Squyres noted. The rock is
clearly highly altered, sporting an unusually low iron content, he said, "which
isn't something we've seen much of before."
Science work at the Independence Rock has been completed. Spirit has resumed
its ascent. "The ground is real solid here, and the climbing is good. I still
don't know if we'll reach the summit or not, but the recent progress has been
excellent," Squyres concluded.
According to rover operator, Jake Matijevic
of the Jet Propulsion Laboratory (JPL), both Spirit and Opportunity
have benefited from clearing skies at the two landing sites.
Furthermore, the rovers have improved energy levels. That is due to dust
clearing events which have been seen on both vehicles, Matijevic reported.
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