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Spirit Marks One Year on Mars (One Martian Year, that is)

November 21, 2005

This image is black and white, and shows a four-foot steel arm bending down into a trench.  The two front rover wheels are visible on the far right and left bottom of the image, and the shadow of the solar panels and the camera and mast reflect on the surface.
NASA's Mars Exploration Rover Spirit casts a shadow over the trench that the rover examined with tools on its robotic arm. Front hazard-avoidance camera image taken on Feb. 21, 2004. Image Credit: NASA/JPL-Caltech
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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.

This image shows a dark tan smooth sky with a rocky, sandy carmel-colored surface with one large hill directly in the center.  Rover tracks come from the middle right of the image from below the side of the hill.  A 1-foot by 1-foot square of the rover's solar panels is in the forground of the picutre.
"Larry's Lookout" panorama camera mosaic, acquired on Spirit's 410th to 413th martian days, or sols (Feb. 27 to Mar. 2, 2005), along the drive up "Husband Hill." Image credit: NASA/JPL-Caltech/Cornell
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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."

This black and white image shows a flat rock-strewn ground stretching a mile to a large hill that rumbles in the distance.  A yellow line meanders straight toward the hill, then once it reaches the hill, it jags to the left, then curves to the right, then curves up and to the left across most of the width of the hill, then straight up for a bit.  Aqua blue words mark about 40 points along the yellow route that the rover stopped and did research.
This image is a simulated 3-D traverse map of Spirit's journey up to its 502nd sol on Mars. Image credit: Ohio State University Mapping and GIS Lab
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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.

This image shows a dark brown dusty surface with a few hand-held-sized slabs of prickly-looking rocks jutting out of the surface.  One ultra-bright white triangular-shaped spot coats the center of the image that has a perfect circle dug in the middle of it.
This image of a very soft, nodular, layered rock nicknamed "Peace" in honor of Martin Luther King Jr. shows a 4.5-centimeter-wide (1.8-inch-wide) hole Spirit ground into the surface with the rover's rock abrasion tool. Image Credit: NASA/JPL-Caltech/Cornell
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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."

This image shows an orange surface coated with blue-grey rocks of various sizes strewn against a small ridge.  Behind the ridge is a vast, flat valley colored light green-grey.
The outcrop shown here was nicknamed "Hillary" for Sir Edmund Hillary, who scaled Mount Everest. This false-color view combines images that Spirit took with its panoramic camera during the rover's 608th sol (Sept. 18, 2005). Image credit: NASA/JPL-Caltech/Cornell
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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.

This image shows two views of a sundial that has a microphone-looking apparatus sticking out of the middle of a square flat base that has colored tabs in each of the four corners.  The tabs are bright green, yello, blue, and red in the first image.  In the second image, the same sundail is coated with a uniform orange dust, and the black microphone-looking piece and the tabs all look the same orange.
These two images from 10 days apart show that dust was removed from the panoramic camera's calibration target. Spirit's panoramic camera took the picture on the left on March 5, 2005 and took the picture on the right on March 15, 2005. Image credit: NASA/JPL-Caltech/Cornell
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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."

In this black-and-white movie clip, a bright whirlwind scoots across the image from left to write, picking up more dust and therefore growing brighter about mid-way through its path across the surface.
A dust devil is seen from Spirit's hillside vantage point on its 459th martian day, or sol (April 18, 2005). The individual images were taken about 20 seconds apart by Spirit's navigation camera.

Image Credit: NASA/JPL-Caltech
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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.

On the left is a Mars Orbital Camera image from Mars Global Surveyor, with a Mars Odyssey THEMIS night-time infrared overlay. The right-hand image shows a portion of a panoramic camera image, revealing Spirit's hilltop view of rough terrain informally named 'Promised Land.'
On the left is a Mars Orbital Camera image from Mars Global Surveyor, with a Mars Odyssey THEMIS night-time infrared overlay. The right-hand image shows a portion of a panoramic camera image, revealing Spirit's hilltop view of rough terrain informally named "Promised Land." Image Credit: NASA/JPL-Caltech/MSSS/ASU/Cornell
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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.
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