After
nearly one year of rolling and scrambling up Husband Hill, NASA's Mars rover
Spirit is headed back down towards new and rocky pastures.
The rover
is making its way down Husband's slopes toward a basin to the south, where a
science target known as "Home Plate"
awaits.
"It is a
big step," said Steve Squyres, principal investigator
of the rover's science mission at Cornell University in Ithaca, New York.
"We've really switched gears."
Spirit's
descent marks a new phase of the rover's Mars exploration, which has carried it
across the plains and up one hill of its Gusev Crater
landing site, Squyres told SPACE.com.
Meanwhile, Opportunity
- Spirit's robotic partner in Mars exploration - has overcome a series of
glitches as it roves around a wide crater dubbed Erebus on the other side of
the red planet.
Hilltop
departure
Spirit reached
the top of Husband Hill, part of the seven-rise Columbia Hills chain, in late
August after steadily scaling 270 feet (82 meters) of rocky terrain.
After
comparing rocks at its summit - the last target, an outcrop dubbed "Hillary,"
required a bit of rover wiggling to observe - with those at lower elevations,
Husband Hill's geology appears to be very similar from the top down, mission
scientists said.
"It's very
similar in composition, with very similar textures when you look at it with a
microscope, but it's dipping in all different directions," Squyres
said of the hill's geology. "What it says is that the geology around here is
pretty complicated."
Husband
Hill's similar composition seems to speak toward a violent beginning,
researchers said, adding that the rise may represent part of an ancient crater rim or have been formed through some other
uplift process.
"My first
personal reaction is that it's maybe not surprising since Mars gets beaten up a
lot by impacts," said Albert Haldemann, rover deputy
project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California,
during an interview, adding that researchers have not settled on an impact as
the hill's genesis.
Spirit is currently
making its may along an area dubbed "Haskin Ridge" and will head toward "Home
Plate," though the science target is not an ultimate goal.
"There's a
lot of good stuff beyond it," Squyres said.
Haldemann
added that it could take two months for Spirit to completely descend Husband
Hill, depending on the number of interesting spots it turns up on the way down.
Opportunity
recovers
On the
plains of Meridiani Planum
on the other side of Mars, Spirit's robotic partner Opportunity is again rolling
westward around Erebus
Crater.
Unlike
Spirit, Opportunity experienced a series of glitches this month that stalled
science operations for several days.
"We had a
little string of bad luck and some hiccups here and there," Haldemann
said.
On Oct. 4 -
its 603rd day, or sol, on Mars - the rover halted a planned 148-foot
(45-meter) drive after just 16 feet (five meters) when its wheels began
slipping in Martian sand. The incident triggered Opportunity's maximum slip
limits, and canceled the drive as a precaution against bogging down, mission
managers said.
But the
unplanned stop was a success of sorts for Opportunity, proving to rover controllers
and mission scientists that the measures taken to prevent the robot from
trapping itself in the Martian sand again work well. The rover bogged
down in a dune for nearly five weeks early this year.
"A sol like
that gives you confidence," Squyres said. "I'm really
convinced now that we're able to keep the vehicle safe."
Opportunity
also experienced two separate computer reboots - one well understood, the other
not so much - that also prevented the robot from carrying out its science
duties. The first reboot was due to a documented flight software glitch, while
the second one also appears familiar to mission scientists.
"The good
news is that it's happened again in the same fashion as it did some 200 sols
ago," Haldemann said of the second reboot glitch.
"And that may help us determine its cause."
But despite
the glitches, Opportunity is again making steady progress around Erebus, a
shallow depression that stretches about 984 feet (300 meters) in diameter.
"We're not
going to take any risks," Squyres said, adding that it's unlikely Opportunity will explore Erebus as in depth as
it did Endurance
Crater. "It's a big crater in terms of diameter, but really shallow. It's
nothing like Endurance."
A
Martian anniversary
While
Spirit and Opportunity have each performed well beyond their initial, 90-day mission
- they've kept scientists on Earth busy for more than one
and a half years - the two rovers still have one distinctively Martian
milestone ahead of them.
But both robots
have to keep roving at just over one more month to make it. Unlike Earth, which
takes about 365 days to circle the Sun, Mars takes about 687 days - or sols -
to make the trip.
On Nov. 21,
Spirit will have spent an entire Martian year trekking across the red planet's
surface, with Opportunity following in turn on Dec. 11.
"I actually
see the Mars year anniversary as being more significant," Squyres
said, "We will have seen Mars over an entire seasonal cycle."
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