GRAIL Reveals Secrets of the Lunar Interior
GRAIL Reveals Secrets of the Lunar Interior — Dr. Patrick J. McGovern, Lunar and Planetary Institute A mini-flotilla of spacecraft sent to the Moon in the past few years by several nations has revealed much about the characteristics of the lunar surface via techniques such as imaging, spectroscopy, and laser ranging. While the achievements of these missions have been impressive, only GRAIL has seen deeply enough to reveal inner secrets that the Moon holds. LRecent Lunar Missions Country Name Launch Date Status ESA Small Missions for Advanced September 27, 2003 Ended with lunar surface impact on Research in Technology-1 (SMART-1) September 3, 2006 USA Acceleration, Reconnection, February 27, 2007 Extension of the THEMIS mission; ended Turbulence and Electrodynamics of in 2012 the Moon’s Interaction with the Sun (ARTEMIS) Japan SELENE (Kaguya) September 14, 2007 Ended with lunar surface impact on June 10, 2009 PChina Chang’e-1 October 24, 2007 Taken out of orbit on March 1, 2009 India Chandrayaan-1 October 22, 2008 Two-year mission; ended after 315 days due to malfunction and loss of contact USA Lunar Reconnaissance Orbiter (LRO) June 18, 2009 Completed one-year primary mission; now in five-year extended mission USA Lunar Crater Observation and June 18, 2009 Ended with lunar surface impact on Sensing Satellite (LCROSS) October 9, 2009 China Chang’e-2 October 1, 2010 Primary mission lasted for six months; extended mission completed flyby of asteroid 4179 Toutatis in December 2012 USA Gravity Recovery and Interior September 10, 2011 Ended with lunar surface impact on I Laboratory (GRAIL) December 17, 2012 To probe deeper, NASA launched the Gravity Recovery and Interior Laboratory (GRAIL) mission: twin spacecraft (named “Ebb” and “Flow” by elementary school students from Montana) flying in formation over the lunar surface, tracking each other to within a sensitivity of 50 nanometers per second, or one- twenty-thousandth of the velocity that a snail moves [1], according to GRAIL Principal Investigator Maria Zuber of the Massachusetts Institute of Technology.
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