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Mark Robert Showalter (born December 5, 1957) is a Senior Research Scientist at the SETI Institute. He is the discoverer of six moons and three planetary rings. He is the Principal Investigator of NASA's Planetary Data System Rings Node, a co-investigator on the Cassini–Huygens mission to Saturn, and works closely with the New Horizons mission to Pluto.〔 〕 ==Biography== Showalter was born in Abington, Pennsylvania. He enjoyed playing with science-themed toys while a child, and later mowed lawns as a teenager so that he might purchase a telescope in high school. He received a Bachelor of Arts in physics and mathematics from Oberlin College in 1979. He was initially undecided about pursuing a career in astronomy after his undergraduate education, but made up his mind after seeing the images of Jupiter sent back to Earth by Voyager 2.〔 〕 Showalter received his MS in astronomy from Cornell University in 1982, and his PhD from Cornell in 1985.〔 His thesis was on Jupiter's ring system, in which he discovered the gossamer ring of Jupiter. In 1990, using ten-year-old Voyager data, Showalter discovered Pan, the eighteenth and innermost moon of Saturn. It orbits within and keeps open the Encke Gap in Saturn's rings via shepherding.〔 〕 In 2003, Showalter and Jack J. Lissauer discovered two new moons of Uranus (Mab and Cupid) in Hubble Space Telescope images.〔 In 2006, they announced the discovery of two very faint rings, the μ and ν rings, within the same data. In 2010, Showalter discovered that spiral vertical corrugations in Jupiter's rings were caused by the impact of Comet Shoemaker–Levy 9 in July 1994. A second smaller set of corrugations appear to be consistent with an unknown impact in early 1990. He and co-researchers also found similar spiral patterns in Saturn's D Ring.〔 〕〔 〕〔 〕 Showalter has assisted the New Horizons team in determining what hazards the spacecraft would encounter as it flew close to Pluto. A search for faint dust rings of Pluto using the Hubble Space Telescope in 2011 led to the discovery of the fourth moon Kerberos.〔 Working with the New Horizons team, Showalter found the fifth moon Styx in July 2012.〔 〕〔 〕 On July 15, 2013, a team of astronomers led by Mark Showalter of the SETI Institute discovered a previously unknown fourteenth moon in images taken by the Hubble Space Telescope from 2004 to 2009. The as yet unnamed fourteenth moon of Neptune, currently known as S/2004 N 1, is thought to measure no more than 20 km in diameter.〔(Beatty, Kelly. "Neptune's Newest Moon." ''Sky and Telescope.'' July 15, 2013. ) Accessed 2013-07-17.〕 The Mars-crossing asteroid 18499 Showalter is named after Dr. Showalter. 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「Mark R. Showalter」の詳細全文を読む スポンサード リンク
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