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Mars encounters cause fresh surfaces on some near-Earth asteroids
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Astronomy and Space Physics.
2014 (English)In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 227, 112-122 p.Article in journal (Refereed) Published
Abstract [en]

All airless bodies are subject to the space environment, and spectral differences between asteroids and meteorites suggest many asteroids become weathered on very short (<1 Myr) timescales. The spectra of some asteroids, particularly Q-types, indicate surfaces that appear young and fresh, implying they have been recently been exposed. Previous work found that Earth encounters were the dominant freshening mechanism and could be responsible for all near-Earth object (NEO) Q-types. In this work we increase the known NEO Q-type sample of by a factor of three. We present the orbital distributions of 64 Q-type near-Earth asteroids, and seek to determine the dominant mechanisms for refreshing their surfaces. Our sample reveals two important results: (i) the relatively steady fraction of Q-types with increasing semi-major axis and (ii) the existence of Q-type near-Earth asteroids with Minimum Orbit Intersection Distances (MOID) that do not have orbit solutions that cross Earth. Both of these are evidence that Earth-crossing is not the only scenario by which NEO Q-types are freshened. The high Earth-MOID asteroids represent 10% of the Q-type population and all are in Amor orbits. While surface refreshing could also be caused by Main Belt collisions or mass shedding from YORP spinup, all high Earth-MOID Q-types have the possibility of encounters with Mars indicating Mars could be responsible for a significant fraction of NEOs with fresh surfaces.

Place, publisher, year, edition, pages
2014. Vol. 227, 112-122 p.
Keyword [en]
Asteroids, Spectroscopy, Near-Earth objects
National Category
Engineering and Technology
URN: urn:nbn:se:uu:diva-218586DOI: 10.1016/j.icarus.2013.09.014ISI: 000329532000011OAI: oai:DiVA.org:uu-218586DiVA: diva2:696276
Available from: 2014-02-13 Created: 2014-02-13 Last updated: 2014-02-13Bibliographically approved

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Lockhart, Matthew
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