Jul 4 2008
From The Space Library
In a series of 11 articles published in the journal Science, researchers reported on the data MESSENGER had gathered during its 14 January 2008 fly-by of Mercury. During the mission, the spacecraft had taken high-resolution images of Mercury’s surface, sampled ions in the planet’s atmosphere, taken altitude measurements, and gathered data on Mercury’s atmospheric composition and surface chemistry. The MESSENGER images settled a scientific debate, which had been ongoing since the 1970s, regarding whether Mercury’s smooth plains had formed from cooled lava or from melted rock resulting from the impact of a large meteor crashing into the planet’s surface. The images showed a topography indicating that lava flows had formed the plains, as well as evidence of volcanoes, including a 60-mile-wide (96.56-kilometer-wide) shield volcano in the Caloris Basin. The MESSENGER data also showed that, as Mercury’s dense core had cooled, the planet had contracted at least 30 percent more than researchers had previously thought. This contraction had affected Mercury’s magnetic field. MESSENGER’s measurements showed that Mercury’s magnetic field is mostly dipolar, like that of Earth. However, Mercury’s magnetic field is much weaker than Earth’s. Because of the planet’s weak magnetic field and close proximity to the Sun, solar winds weather Mercury’s atmosphere and surface chemistry. Scientists hoped that Mercury’s “space weathering” would help them measure the age of the planet’s geographical features.
NASA, “NASA Reveals New Discoveries from Mercury,” news release 08-166, 3 July 2008, http://www.nasa.gov/home/hqnews/2008/jul/HQ_08166_Messenger_Mercury.html (accessed 26 May 2001); Andrea Thompson, “Volcanoes on Mercury Solve 30-Year Mystery,” Space.com, 3 July 2008, http://www.space.com/5589-volcanoesmercury- solve-30-year-mystery.html (accessed 26 May 2011).
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