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Giant Impacts and the Distribution of Planetary ObliquitiesWe have conducted a set of approximately 200 numerical experiments to test the hypothesis that a giant impact leading to the formation of Earth's Moon could have occurred tens of millions of years after most of the small debris in the inner Solar System had been incorporated into terrestrial planets or been removed from the region. More than half of these simulations ended with a giant impact between two of the five terrestrial planets that were initially present. Neglecting any rotational angular momentum prior to the collision, the merged planet typically has a rotation period of less than five hours. The mean planetary obliquity is 91.7 degrees, and the median is 87.9 degrees; thus, there is no statistically significant difference between the number of bodies with prograde rotation and the number with retrograde rotation. There is a paucity of planets with obliquity close to 90 degrees, but the total number of impacts was too small for this result to be of much significance. Several encounters leading to collisions are dominated by three-body effects, with the velocity at impact being slightly less than the free-space escape velocity of the two bodies; the obliquity distribution produced by these impacts appears to be random.
Document ID
20000121339
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Lissauer, Jack J.
(NASA Ames Research Center Moffett Field, CA United States)
Rivera, E. J.
(State Univ. of New York Stony Brook, NY United States)
Duncan, M. J.
(Queens Univ. Unknown)
Levison, H. F.
(Southwest Research Inst. United States)
DeVincenzi, Donald L.
Date Acquired
August 19, 2013
Publication Date
January 1, 2000
Subject Category
Astrophysics
Meeting Information
Meeting: Dynamical Astronomy
Location: Yosemite, CA
Country: United States
Start Date: April 8, 2000
End Date: April 18, 2000
Funding Number(s)
CONTRACT_GRANT: NAG5-4640
PROJECT: RTOP 344-30-50-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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