The inner solar system's biggest and most recent known collision was the Moon-forming giant impact between a large protoplanet and proto-Earth. Not only did it create a disk near Earth that formed the Moon, it also ejected several percent of an Earth mass out of the Earth-Moon system. Here, we argue that numerous kilometer-sized ejecta fragments from that event struck main-belt asteroids at velocities exceeding 10 kilometers per second, enough to heat and degas target rock. Such impacts produce ~1000 times more highly heated material by volume than do typical main belt collisions at ~5 kilometers per second. By modeling their temporal evolution, and fitting the results to ancient impact heating signatures in stony meteorites, we infer that the Moon formed ~4.47 billion years ago, which is in agreement with previous estimates.

Department of Earth Sciences Western University London ON Canada

Hawai'i Institute of Geophysics and Planetology University of Hawai'i at Manoa Honolulu Hawai'i 96822 USA

Institute of Astronomy Charles University 5 Holešovičkách 2 CZ 18000 Prague 8 Czech Republic

Lunar and Planetary Laboratory University of Arizona Tucson AZ USA SSERVI Center for Lunar Science Exploration Houston TX USA

Southwest Research Institute and NASA Solar System Exploration Research Virtual Institute Boulder CO USA

Science. 2015 Apr 17;348(6232):271. doi: 10.1126/science.348.6232.271. PubMed

Citace poskytuje Crossref.org

Infrared Spectra of Small Radicals for Exoplanetary Spectroscopy: OH, NH, CN and CH: The State of Current Knowledge