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NASA's Mars Exploration Rover Mission (MER) is an ongoing robotic space mission involving two rovers, ''Spirit'' and ''Opportunity'', exploring the planet Mars. It began in 2003 with the sending of the two rovers—MER-A ''Spirit'' and MER-B ''Opportunity''—to explore the Martian surface and geology. The mission's scientific objective was to search for and characterize a wide range of rocks and soils that hold clues to past water activity on Mars. The mission is part of NASA's Mars Exploration Program, which includes three previous successful landers: the two Viking program landers in 1976 and Mars Pathfinder probe in 1997.〔(【引用サイトリンク】 title=Mars Exploration Rover Mission Overview )〕 The total cost of building, launching, landing and operating the rovers on the surface for the initial 90-sol primary mission was US$820 million. Since the rovers have continued to function beyond their initial 90 sol primary mission, they have each received five mission extensions. The fifth mission extension was granted in October 2007, and ran to the end of 2009.〔〔(【引用サイトリンク】title=Mars Exploration Rover Mission: Press Releases )〕 The total cost of the first four mission extensions was $104 million, and the fifth mission extension is expected to cost at least $20 million.〔 In July 2007, during the fourth mission extension, Martian dust storms blocked sunlight to the rovers and threatened the ability of the craft to gather energy through their solar panels, causing engineers to fear that one or both of them might be permanently disabled. However, the dust storms lifted, allowing them to resume operations.〔(【引用サイトリンク】 Mars Exploration Rover Status Report: Rovers Resume Driving )〕 On May 1, 2009, during its fifth mission extension, ''Spirit'' became stuck in soft soil on Mars. After nearly nine months of attempts to get the rover back on track, including using test rovers on Earth, NASA announced on January 26, 2010 that ''Spirit'' was being retasked as a stationary science platform. This mode would enable ''Spirit'' to assist scientists in ways that a mobile platform could not, such as detecting "wobbles" in the planet's rotation that would indicate a liquid core.〔(【引用サイトリンク】title=Now a Stationary Research Platform, NASA's Mars Rover Spirit Starts a New Chapter in Red Planet Scientific Studies )〕 Jet Propulsion Laboratory (JPL) lost contact with Spirit after last hearing from the rover on March 22, 2010 and continued attempts to regain communications lasted until May 25, 2011, bringing the elapsed mission time to 6 years 2 months 19 days, or over 25 times the original planned mission duration.〔(【引用サイトリンク】url=http://www.jpl.nasa.gov/news/news.cfm?release=2011-156&cid=release_2011-156 )〕 In recognition of the vast amount of scientific information amassed by both rovers, two asteroids have been named in their honor: 37452 Spirit and 39382 Opportunity. The mission is managed for NASA by the Jet Propulsion Laboratory, which designed, built, and is operating the rovers. On January 24, 2014, NASA reported that current studies by the ''Curiosity'' and ''Opportunity'' rovers will now be searching for evidence of ancient life, including a biosphere based on autotrophic, chemotrophic and/or chemolithoautotrophic microorganisms, as well as ancient water, including fluvio-lacustrine environments (plains related to ancient rivers or lakes) that may have been habitable. The search for evidence of habitability, taphonomy (related to fossils), and organic carbon on the planet Mars is now a primary NASA objective.〔 ==Objectives== The scientific objectives of the Mars Exploration Rover mission are to:〔(【引用サイトリンク】title=The scientific objectives of the Mars Exploration Rover )〕 *Search for and characterize a variety of rocks and soils that hold clues to past water activity. In particular, samples sought include those that have minerals deposited by water-related processes such as precipitation, evaporation, sedimentary cementation, or hydrothermal activity. *Determine the distribution and composition of minerals, rocks, and soils surrounding the landing sites. *Determine what geologic processes have shaped the local terrain and influenced the chemistry. Such processes could include water or wind erosion, sedimentation, hydrothermal mechanisms, volcanism, and cratering. *Perform calibration and validation of surface observations made by Mars Reconnaissance Orbiter instruments. This will help determine the accuracy and effectiveness of various instruments that survey Martian geology from orbit. *Search for iron-containing minerals, and to identify and quantify relative amounts of specific mineral types that contain water or were formed in water, such as iron-bearing carbonates. *Characterize the mineralogy and textures of rocks and soils to determine the processes that created them. *Search for geological clues to the environmental conditions that existed when liquid water was present. *Assess whether those environments were conducive to life. During the last two decades, NASA will conduct several missions to address whether life ever existed on Mars. The search begins with determining whether the Martian environment was ever suitable for life. Life, as humans understand it, requires water, hence the history of water on Mars is critical to finding out if the Martian environment was ever conducive to life. Although the Mars Exploration Rovers do not have the ability to detect life directly, they offer important information on the habitability of the environment in the planet's history 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mars Exploration Rover」の詳細全文を読む スポンサード リンク
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