HR: 14:55h
AN: P43C-05 INVITED    [Abstracts]
TI: Moon geophysics and Lunar environemental monitoring: Apollo data reprocessing and perspectives with the MoonTwin project.
AU: * Lognonné, P
EM: lognonne@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, Géophysique Spatiale et Planétaire, 4 Avenue de Neptune, Saint Maur des Fosse, 94100, France
AU: Regnier, P
EM: pascal.regnier@astrium.eads.net
AF: Astrium SAS, Future Programmes and Proposals division, 31, rue des Cosmonautes, Toulouse, 31402, France
AU: Team, a
AB: The formation of the Moon is probably results from a large impact between a Mars-sized planet and the Earth. The size of the Moon's core, the thickness of the crust and the structure of the lunar mantle are among the few parameters able to constrain this impact, along with the depth and vigor of the magma ocean that appeared on the young moon, after re-accretion around Earth's orbit. These parameters are therefore crucial to understand how our planet was affected by the impact, from both the energetic and volatile budget point of view, and how a body like the moon evolves. The reprocessing of the data recorded by the 4 ALSEP stations (Apollo 12, 14, 15 and 16), which were the first and, to date, the only successful geophysical stations in Planetary sciences, have shed new light on the interior of the Moon and in the determination of the parameters listed above. Very large uncertainties however remain. A first example is in the crustal thickness. The seismic crustal thickness estimates vary from 58 km to 30±5 km near the Apollo 12 landing site. When the lateral variations are taken into account, a mean crustal thickness beneath the Apollo stations of 34±5 km is found. Comparable uncertainties are found in the deep structure of the Moon, which is not directly constrained by seismology. Interior structure models obtained from joint inversion of the density, moment of inertia, Love number (k₂) and using the seismic data apriori for the upper mantle and middle mantle show that a wide range of acceptable core models with 1%-2% lunar mass fit the data.These two extreme examples of lunar interior structure show that large uncertainties remain. Most are related to the lack of goo geophysical data. The Apollo seismometers had limited performance, especially in terms of frequency bandwidth and limited coverage of th network. Only two heat flow measurements were made by Apollo and all geodetic beacons are close to the equator; Other are related to the large lateral variations, already detected in the crustal thickness, and probably also existing in the lunar mantle. Consequently,most of the geophysical methods developed during the last two decades (e.g. long period body waves inversions, free oscillations inversions, receiver function analysis, etc) cannot be used on the Moo data. The deployment of a new network of geophysical stations on the Moon is therefore the aim of several projects in USA and Europe. We focus here on the MoonTwin project. The goal of the MoonTwin is to deploy 2 landers on the Moon, including one near the south pole, and is proposed as the NEXT mission of the ESA AURORA program. These landers will first perform severa technology demonstrations necessary to future MSR missions including a precision soft landing. After landing, science of the Moon and from the Moon will be performed.In addition to the geophysical objectives described above, which can be accomplished by seismometry, geodetic, heat flow measurements and magnetometry, other objectives more related to exploration and Science on the Moon will be covered: the first one will be to better understand and monitor the potential hazard lunar seismic events pose to a permanent habitat on the Moon, the rate of micrometeoroides impacts and the level of radiation. The second one will be to perform a first pilot experiment of radio-astronomy on the Moon, by using the benefit of the polar station, which will be regularly in occultation from the Earth radio-astronomical noise.
DE: 5418 Heat flow
DE: 5430 Interiors (8147)
DE: 5440 Magnetic fields and magnetism
DE: 5455 Origin and evolution
DE: 6250 Moon (1221)
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting