[meteorite-list] Spirit Marks One Year on Mars (One Martian Year, that is)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Nov 21 18:30:33 2005
Message-ID: <200511212329.jALNT4D29197_at_zagami.jpl.nasa.gov>

http://marsrovers.jpl.nasa.gov/spotlight/spirit/20051121.html

Spirit Marks One Year on Mars (One Martian Year, that is)
Jet Propulsion Laboratory
November 21, 2005

Spirit, the untiring robotic "wonder child" sent by NASA to explore the
eerily earthlike fourth planet from the sun, has completed one martian
year--that's almost two Earth years--on Mars. Designed to last only 90
martian days (sols), the six-wheeled marvel the size of a golf cart has
pursued a steady course of solar-driven geologic fieldwork, bringing
back some 70,000 images and a new understanding of Mars as a potential
habitat.

During Spirit's martian year, the seasons have changed from summer to
winter and back again. In its orbit around the Sun, Mars has returned to
where it was when the rover first landed. Having survived seven times
its expected lifetime and traveling over 3 miles (about 5,000 meters),
Spirit is still going strong.

Hill Climbing with Spirit

"When we first took a look around after landing," noted Cornell
geologist and principal investigator Steve Squyres, "the 'Columbia
Hills' seemed impossibly far away. Given its longer life, though, Spirit
reached them and became the first explorer to climb a mountain on
another planet. 'Husband Hill' is about as tall as the Statue of
Liberty, but for a little rover, that was a heck of a climb."

To achieve that feat, Spirit's handlers painstakingly plotted a path up
the slopes to keep the rover alive during the colder months of the
martian year. A few months into the mission, winter was fast approaching
and the Sun was ever lower above the northern horizon.

"We followed a circuitous path uphill, using the higher, uneven terrain
to tilt the solar panels toward the Sun, keep the communications antenna
facing Earth, and avoid rocks along the way," said rover driver Chris
Leger at NASA's Jet Propulsion Laboratory.

While keeping warm in the winter, Spirit's uphill battle also centered
on what NASA sent both rovers to find: signs of past water on Mars. If
water persisted for long periods of time in martian history, the red
planet might have once had a life-supporting environment. At first,
Spirit's studies showed plenty of volcanic rocks, but few signs of
minerals formed by water.

"Only by climbing did Spirit find what we were seeking," said Ray
Arvidson, deputy principal investigator from Washington University in
St. Louis. "With Spirit's engineering stamina, we finally found rocks in
the 'Columbia Hills' that either formed in, or were altered by, water.
Perhaps best of all, the hills hold the highest sulfur content ever
found on Mars: sulfate salts, deposited by water."

Besides finding these prized signs of past water on Mars, Spirit has
discovered at least five distinct classes of rocks. Among these are
molten rocks blasted upward and outward during meteorite impacts,
materials formed during violent volcanic explosions, and lava flows.
Beyond these large features, Spirit has taken a close look at
grain-sized rock particles as well. "At a small scale, the geology of
'Husband Hill' looks like it's been put in a blender," said Squyres.

"All of this variety churned up in the rock record shows how volatile
Mars was in the past," Arvidson says. "Rocks in one layer say volcanoes
were exploding, in another that lava was flowing, in another that water
was seeping. And then imagine that some massive geologic force uplifted
the whole of 'Columbia Hills,' exposing all of these layers to millions
of years of wind erosion, gravity-driven landslides, and meteorite
impacts."

Seeing this rich geologic record on the north side of the Columbia
Hills, Arvidson says, heightens the science team's anticipation of what
more they will learn about the history of the hills during Spirit's trek
down the other side.

Raising Spirit's Energy

For Spirit's continued journey, engineers are delighted with the
unlikely role the martian wind has played in increasing the rover's
staying power. A peak threat of wind is the planet-encircling dust
storms that can arise in martian spring through early summer, blocking
out sunlight needed for power. "Luckily," said project scientist Joy
Crisp, "we haven't yet seen a global dust storm since the rovers landed
on Mars, but we have seen a lot of dust devils."

Dust devils occur when the wind whirls over the surface, stirring dust
up like a miniature tornado and traveling up to 13 feet per second (4
meters per second). It turns out the dust devils are primarily a
lunchtime affair, mostly occurring between 11 a.m. and 3 p.m. at each
rover site. For both rovers, these noontime winds have been very favorable.

While dozens of dust devils have passed before Spirit's cameras, some
have made contact, sweeping dust from the rover's solar panels. The
solar panels are then able to take in more sunlight and convert it into
electricity, keeping Spirit "alive" for even longer.

Keeping Spirit Alive

While no one can predict how long Spirit will last, the rover's stamina
throughout the long martian year encourages hope. The science team is
busy even now plotting new destinations to strive toward. If the
"Columbia Hills" were once a distant dream, new far-off horizons beckon
just as much. Getting there will stretch the rover's capabilities as
much as the imagination. Team member Jim Rice calls one such distant
target, a rough and rugged terrain to the south, "the Promised Land."

One thing is sure. No matter what the future holds, Spirit is already
there.
Received on Mon 21 Nov 2005 06:29:04 PM PST