Computer simulation model for early post-capture phase of lunar orbital evolution: implications for thermal history of Earth and Moon
Gravitational capture of a lunar-sized body entails dissipation of about 2 x 10/sup 35/ ergs within the bodies of Earth and Moon by body tides during a close gravitational encounter. For capture to occur, the deformation constants (Love numbers) must be sufficiently high and Q (specific energy dissipation factor) must be sufficiently low. Initial conditions for the two-body orbital simulation are perigee = 20 R/sub e/ (Earth radii), apogee = 270 R/sub e/, and semi-minor axis = 73 R/sub e/. This early post-capture orbit has angular momentum equivalent to a circular lunar orbit of 40 R/sub e/. For simplification, the effects of Earth rotation are neglected and Love numbers are held constant during each calculation. The main variable controlling orbital evolution is Q. Since about 7 x 10/sup 35/ ergs must be dissipated for capture and subsequent orbital circularization, the bodies of both Earth and Moon are heated considerably. Using the Love numbers given above, about 10% of the energy goes to Earth and about 90% goes to Moon. Although the 10% allocated to Earth would be sufficient to melt only a thin zone of mantle material, the combination of energy dissipation and tidal action during such as orbital circularization scenario could lead to enhanced rates of crustal spreading and subduction on an already warm Earth. The authors think that this thermal episode may be sufficient to cause widespread destruction and/or metamorphism of the ancient crust of Earth. They suggest that lunar capture and subsequent early geocentric orbital evolution occurred about 3.9 billion years ago.
- Research Organization:
- Denison Univ., Granville, OH (USA)
- OSTI ID:
- 6191839
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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GENERAL PHYSICS
58 GEOSCIENCES
EARTH PLANET
GRAVITATIONAL INTERACTIONS
PLANETARY EVOLUTION
MOON
COMPUTERIZED SIMULATION
EARTH CRUST
EARTH MANTLE
GEOLOGIC HISTORY
GRAVITATION
LUNAR ATMOSPHERE
PLATE TECTONICS
TEMPERATURE MEASUREMENT
ATMOSPHERES
BASIC INTERACTIONS
INTERACTIONS
PLANETS
SATELLITE ATMOSPHERES
SATELLITES
SIMULATION
SOLAR SYSTEM EVOLUTION
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640107* - Astrophysics & Cosmology- Planetary Phenomena
580100 - Geology & Hydrology- (-1989)