page_title: Spirit (rover)
section_title: Plains
hierarchical_section_title: Spirit (rover) / Discoveries / Plains
caption_attribution_description: English: Adirondack Rock on Mars, imaged by Mars rover Spirit Credit: NASA/JPL
context_page_description: Spirit, also known as MER-A or MER-2, is a robotic rover on Mars, active from 2004 to 2010. It was one of two rovers of NASA's Mars Exploration Rover Mission. It landed successfully within the impact crater Gusev on Mars at 04:35 Ground UTC on January 4, 2004, three weeks before its twin, Opportunity, which landed on the other side of the planet. Its name was chosen through a NASA-sponsored student essay competition. The rover became stuck in a "sand trap" in late 2009 at an angle that hampered recharging of its batteries; its last communication with Earth was sent on March 22, 2010.
  The rover completed its planned 90-sol mission. Aided by cleaning events that resulted in more energy from its solar panels, Spirit went on to function effectively over twenty times longer than NASA planners expected. Spirit also logged 7.73 km of driving instead of the planned 600 m, allowing more extensive geological analysis of Martian rocks and planetary surface features. Initial scientific results from the first phase of the mission were published in a special issue of the journal Science.
  On May 1, 2009, Spirit became stuck in soft sand.
context_section_description: 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.
  Plains 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.
  One sign that they were altered was that it was easier to grind these rocks compared to the same types of rocks found on Earth.
caption: Rat post grind.jpg
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