Almost by accident, NASA's
Mars rover Opportunity has found a rock that may point to a second water event
in the red planet's past.
The rover was backing away
from potentially treacherous, sandy terrain at the bottom of Endurance Crater
when its cameras came across "Escher," an oddly cracked rock that
researchers said may have fractured after being soaked during some sort of
water event.
But more evidence is needed
to be sure.
"There may have been
some frost, some water present, but it's not a definite result," said
Steve Squyres, the rover mission's principal investigator, adding that some
follow up observations at a rock called "Wopmay" may shed more light.
"Our hope is that it will reveal more to us about the possibility of a
secondary water episode."
If verified, it would point
to a secondary water episode that occurred after Endurance Crater formed
on the plains of Meridiani Planum, Opportunity's landing site.
The robust rover has
already found evidence indicating the region was initially
soaked in the distant past, prior to the crater's formation, Squyres said.
Squyres and other mission
scientists discussed the current progress of Opportunity and its robotic twin
Spirit during an Oct. 7 teleconference that connected researchers from Cornell
University, Massachusetts Institute of Technology (MIT) and NASA's Jet
Propulsion Laboratory (JPL) in Pasadena, California.
Puzzling
"Escher"
The tantalizing prospect
popped up when Opportunity found "Escher" cracked and fractured into
polygonal shapes. On Earth, such polygonal rock patterns have been known to be
associated with water, but they could just as well have formed when an impact
smacked into the surface elsewhere on Meridiani Planum, researchers said.
"As the [Earth] rock
dries out, it reduces its volume and contracts in all directions,"
explained John Grotzinger, a rover science team member from the MIT. "This
is not to say these [Mars formations] aren't tectonic, but we have to consider
this water option as well."
Opportunity drilled into
"Escher's" surface with its arm-mounted rock abrasion tool (RAT),
finding the chemistry of its innards substantially different from its surface.
While that hints at a possible past interaction with water, "Escher"
is the first Martian rock in which the polygonal patterns have been found and
its flat orientation on the floor of Endurance Crater poses a limited view into
the rock's history.
Wopmay, which researchers
said shows some similarities with Escher, stands upright on the Martian surface
and could answer questions its predecessor leaves outstanding.
"If you're going to
reach a conclusion for water, you're going to need all the data," Squyres
said.
Spirit pushes forward
Opportunity is not alone in
making new discoveries.
Sitting atop the West Spur
of the Columbia Hills in its Gusev Crater landing site, Spirit overcame a
recent steering problem to study the nearby rock
"Ebenezer," which appears to reinforce views that water once soaked
the hilly region, researchers said.
"We're beginning to
suspect that almost all of the rocks in Columbia Hills look like this,"
Squyres said, adding that while "Ebenezer" differs in outward
appearance from other nearby rocks, their chemical signatures all indicate past
interactions with water.
Meanwhile, Spirit's
panoramic camera snapped a new vista dubbed Cahokia from its West Spur perch,
which includes a clear, 50-mile (80-kilometer) view to the very edge of Gusev
Crater.
"It's a spectacular
view," said Jim Bill, rover lead scientist for panoramic cameras at
Cornell University, adding that the image was taken over 10 Martian days - or
sols - and relayed to Earth over a period of weeks.
Rover engineers are still
trying to understand the exact nature of Spirit's steering glitch, which
apparently cleared up on its own. While Spirit is again mobile, engineers hope
to prepare a plan to handle the problem should it occur again.
"We don't have a root
cause for this event yet but as they age we'll see more aches and pains,"
said Jim Erickson, rover project manager at JPL. "We'll just have to deal
with the problems as they go."
Next up for Spirit is the
summit of nearby Husband Hill, while Opportunity will complete its Wopmay
studies and finally head to the rock outcrop of Burns Cliff on the rim of
Endurance Crater.
"We've got a lot of
good stuff ahead of us," Squyres said.
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