Gusev is a crater on the planet Mars and is located at 14.5°S 175.4°E / -14.5; 175.4 and is in the Aeolis quadrangle. The crater is about 166 kilometers in diameter and formed approximately three to four billion years ago. It was named after Russian astronomer Matvey Gusev (1826–1866) in 1976. Prior to the exploration of the crater by the Spirit Rover, the crater was postulated to be an ancient lakebed with Ma'adim Vallis draining into it, of volcaniclastic origin, or a combination of both. These interpretations were based on Viking orbiter imagery, MOC imagery, THEMIS thermal mapping, and MOLA elevation mapping. However, Spirit did not find any lacustrine deposits, instead Spirit found alkaline volcanic rocks, including olivine basalt, comminuted basaltic debris, lavas, and pyroclastic rocks, but no eruption centers.
More recently, satellite images showed the trails of dust devils on Gusev's floor. The Spirit rover later photographed dust devils from the ground, and likely owes much of its longevity to dust devils cleaning its solar panels. On January 3, 2004, Gusev was the landing site of the first of NASA's two Mars Exploration Rovers, named Spirit. It was hoped that the numerous smaller and more recent craters in this region would have exposed sedimentary material from early eras, although at first the region proved disappointing in its lack of available bedrock for study on the flat lava plains of the crater. It eventually arrived at the Columbia Hills, however, and rocks examined in that region showed evidence of small amounts of briny (salty) water interacting with them in ancient times, although not nearly as much as at Meridiani Planum, the landing area for Spirit's twin, Opportunity. In 2009, Spirit became stuck in the soil of the region, and in 2010 went offline after a harsh Martian winter. Gusev was also considered a potential landing site for the Mars 2020 Perseverance rover.
Spirit Rover's rocks and minerals discoveries on Mars The rocks on the plains of Gusev are a type of basalt. They contain the minerals olivine, pyroxene, plagioclase, and magnetite, and they look like volcanic basalt as they are fine-grained with irregular holes (geologists would say they have vesicles and vugs). Much of the soil on the plains came from the breakdown of the local rocks. Fairly high levels of nickel were found in some soils; probably from meteorites. Analysis shows that the rocks have been slightly altered by tiny amounts of water. Outside coatings and cracks inside the rocks suggest water deposited minerals, maybe bromine compounds. All the rocks contain a fine coating of dust and one or more harder rinds of material. One type can be brushed off, while another needed to be ground off by the Rock Abrasion Tool (RAT). There are a variety of rocks in the Columbia Hills (Mars), some of which have been altered by water, but not by very much water. The dust in Gusev Crater is the same as dust all around the planet. All the dust was found to be magnetic. Moreover, Spirit found the magnetism was caused by the mineral magnetite, especially magnetite that contained the element titanium. One magnet was able to completely divert all dust hence all Martian dust is thought to be magnetic. The spectra of the dust was similar to spectra of bright, low thermal inertia regions like Tharsis and Arabia that have been detected by orbiting satellites. A thin layer of dust, maybe less than one millimeter thick covers all surfaces. Something in it contains a small amount of chemically bound water.
Plains Observations of rocks on the plains show they contain the minerals pyroxene, olivine, plagioclase, and magnetite. These rocks can be classified in different ways. The amounts and types of minerals make the rocks primitive basalts—also called picritic basalts. The rocks are similar to ancient terrestrial rocks called basaltic komatiites. Rocks of the plains also resemble the basaltic shergottites, meteorites that came from Mars. One classification system compares the amount of alkali elements to the amount of silica on a graph; in this system, Gusev plains rocks lie near the junction of basalt, picrobasalt, and tephrite. The Irvine-Barager classification calls them basalts. Plain's rocks have been very slightly altered, probably by thin films of water because they are softer and contain veins of light-colored material that may be bromine compounds, as well as coatings or rinds. It is thought that small amounts of water may have gotten into cracks inducing mineralization processes. Coatings on the rocks may have occurred when rocks were buried and interacted with thin films of water and dust. It was noted that these rocks were easier to grind compared to their Earth counterparts.
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