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The exploration of Mars is the study of Mars by spacecraft. Probes sent from Earth beginning in the late 20th century have yielded a dramatic increase in knowledge about the Martian system, focused primarily on understanding its geology and habitability potential. Engineering interplanetary journeys is very complicated, so the exploration of Mars has experienced a high failure rate, especially in earlier attempts. Roughly two-thirds of all spacecraft destined for Mars failed before completing their missions, and there are some that failed before their observations could begin. However, missions have also met with unexpected levels of success, such as the twin Mars Exploration Rovers operating for years beyond their original mission specifications. As of 24 September 2014, there are two scientific rovers on the surface of Mars beaming signals back to Earth (''Opportunity'' of the ''Mars Exploration Rover'' mission, and ''Curiosity'' of the ''Mars Science Laboratory'' mission), and five orbiters currently surveying the planet: ''Mars Odyssey'', ''Mars Express'', ''Mars Reconnaissance Orbiter'', ''Mars Orbiter Mission'' and MAVEN. To date, no sample return missions have been attempted for Mars, and one attempted return mission for Mars' moon Phobos (''Fobos-Grunt'') has failed. On 24 January 2014, NASA reported that current studies on the planet Mars 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.〔 ==Martian system== Mars has long been the subject of human fascination. Early telescopic observations revealed color changes on the surface that were originally attributed to seasonal vegetation as well as apparent linear features that were ascribed to intelligent design. These early and erroneous interpretations led to widespread public interest in Mars. Further telescopic observations found Mars' two moons, Phobos and Deimos, the polar ice caps, and the feature now known as Olympus Mons, the solar system's tallest mountain. These discoveries piqued further interest in the study and exploration of the red planet. Mars is a rocky planet, like Earth, that formed around the same time, yet with only half the diameter of Earth, and a far thinner atmosphere, it has a cold and desert-like surface. It is notable, however, that although the planet has only one quarter of the ''surface area'' of the Earth, it has about the same ''land area'', since only one quarter of the surface area of the Earth is land. 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「Exploration of Mars」の詳細全文を読む スポンサード リンク
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