http://www.sciencemag.org/content/321/5885/82.abstract
http://www.sciencemag.org/content/333/6051/1859
http://www.nasa.gov/mission_pages/messenger/media/Telecon20110929.html
http://www.sciencemag.org/content/321/5885/82.abstract
http://www.sciencemag.org/content/333/6051/1859
http://www.nasa.gov/mission_pages/messenger/media/Telecon20110929.html