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
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
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,
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
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
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
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,