On challenging slopes that NASA’s Mars rovers began exploring this
month, both Spirit and Opportunity have found new surprises for the
folks back home.
Spirit rolled up to a knobby rock just past where the “Columbia Hills”
start to rise from the surrounding plain. It touched the rock with a
mineral-identifying instrument at the tip of its robotic arm and
detected hematite. Hematite identified from orbit was NASA’s key
reason for choosing Opportunity’s landing site halfway around Mars
from these hills within Gusev Crater.
Opportunity, continuing its descent into “Endurance Crater,” has found
unexpected similarities between lower layers of rock it is examining
for the first time and an overlying layer at “Eagle Crater” where,
months ago, the rover discovered evidence that water once soaked the
area.
“It’s gratifying how well these machines keep performing, considering
they’ve now nearly doubled their original three-month missions on
Mars,” said Chris Voorhees, rover mechanical systems engineer at
NASA’s Jet Propulsion Laboratory, Pasadena, Calif. By the end of next
week, Spirit will have worked on Mars for half a year. It has driven
more than three times the design requirement of one kilometer (0.6
mile). The only symptom of wear or aging on either rover so far is
increased friction in one wheel on Spirit. The rover team at JPL is
beginning to consider good sites for the solar-powered robots to spend
the period of martian winter when reduced daily sunshine cuts power
supply to a minimum. In the nearer term, though, team members are
eager to follow through on the new scientific findings.
Spirit’s hematite finding is in a rock dubbed “Pot of Gold,” about the
size of a softball. “This rock has a shape as if somebody took a
potato and stuck toothpicks in it, then put jelly beans on the ends of
the toothpicks,” said Dr. Steve Squyres of Cornell University, Ithaca,
N.Y., principal investigator for the rovers’ science instruments. “How
it got this crazy shape is anyone’s guess. I haven’t even heard a good
theory yet.”
Dr. Doug Ming, a rover science-team member from NASA’s Johnson Space
Center, Houston, said, “There’s apparently some type of weathering, a
removal of material, but we’re still trying to determine whether it’s
by chemical or mechanical processes.”
Further study of Pot of Gold could also help scientists assess what
the hematite in it tells about past environmental conditions.
“Hematite can form in a few different ways. Most of them require
water, but it can also result from a dry, thermal oxidation process,”
Ming said. “It was hematite identified from orbit that made Meridiani
Planum a compelling place to send Opportunity. There, we’ve learned
that the hematite is indeed part of a water story. At Gusev we’re just
at the starting stage.”
After examining Pot of Gold with the microscopic imager and two
spectrometers on Spirit’s arm, the rover backed away from the rock to
re-approach at a better angle for using its rock abrasion tool to
expose the rock’s interior. In the rough and slippery terrain, that
maneuver took several days. The Other nearby rocks may also be
inspected before Spirit resumes longer drives exploring the Columbia
Hills area. Also, engineers are planning an attempt to redistribute
lubricant in Spirit’s balky right front wheel before the rover leaves
its current vicinity.
Team members presented both rovers’ status at a press conference at
JPL today. Opportunity has driven far enough into the stadium-sized
Endurance Crater to put it within arm’s reach of three layers of rock
beneath a sulfate-rich layer. That area is similar to what
Opportunity first examined in the shallower “Eagle Crater,” where it
landed in January. “We’re trying to systematically characterize the
stratigraphy of the crater as we drive down, analyzing each unit
chemically and mineralogically with all the instruments available,”
said Nicholas Tosca, a science-team affiliate from the State
University of New York, Stony Brook. The first two newly accessed
layers resemble the upper layer in having sulfate salts and spherical
concretions; both are signs of formation of the rocks under wet
conditions.
Squyres said, “I had thought we might see just basalt below the top
salty layer, but instead it’s salty as far as we’ve been able to see
so far. Every time we see more sulfates as we work down this stack, it
adds to the amount of water that was necessary to make this happen.”
JPL, a division of the California Institute of Technology in Pasadena,
manages the Mars Exploration Rover project for NASA’s Office of Space
Science, Washington, D.C. Images and additional information about the
project are available from JPL at http://marsrovers.jpl.nasa.gov and
from Cornell University, at http://athena.cornell.edu .
