ESA Science & Technology - Crater Gassendi

AMIE obtained these images on 13 January 2006, one minute apart from each other, at a distance of about 1220 kilometres (top frame) and 1196 kilometres (bottom frame) from the surface, with a ground resolution of 110 and 108 metres per pixel, respectively.

The area shown in the top image is centred at a latitude of 16.2° South and longitude 40.2° West, while the bottom images is centred at a latitude of 17.9° South and longitude 40.2° West.

Gassendi is an impact feature located on the near side of the Moon, at the northern edge of Mare Humorum. With a diameter of just over 100 kilometres, the crater is much larger than the field of view visible in this image. The hills on the lower right of the mosaic are the central peak of the crater, with a height of roughly 1.2 kilometres. The smaller crater at the top of the image is Gassendi A.

The age of crater Gassendi is estimated to be 3.6 ± 0.7 billion years. After its formation, the crater was filled by lava from the outside. The cracks and faults in the lava floor are a result of the thermal history of Mare Humorum.

Gassendi is a scientifically interesting site offering the possibility of sampling ancient highland rocks in the crater's central peak as well as providing ages for both the Humorum basin impact and the crater Gassendi impact. Gassendi was considered as one of the three potential landing sites for the Apollo 17 mission, which eventually landed in the Taurus-Littorw valley. The terrain just outside the planned landing site at Gassendi is quite rough, and if the crew had landed in this region, it was not certain that they could achieve the primary objective of sampling Gassendi's central peaks.

According to Raitala (1977), most recent tectonically notable lunar surface structures, straight or arcuate rilles and mare ridges (as in Mare Humorum) are found to form regional lineament sets which are interpreted to be manifestations of crustal zones of weakness. Some parts of these zones may have undergone similar development to those of both experimental and natural strike-slip shears.

The crater Gassendi has a spectral relative reflectivity curve that's different from any other lunar crater (Mikhail 1979). High spatial resolution multispectral mapping of Gassendi has been performed in seven bands in the near-IR spectral interval by Chevrel and Pinet (1990, 1992).

Two spectral units associated with photogeologically identified extrusive volcanic materials display absorptions around 1 μm, indicating the presence of materials with clinopyroxene and/or olivine as a major mafic component. The presence of extrusive volcanic materials that have either been photogeologically identified and/or spectrally identified is limited to the southern portion of Gassendi's floor, which is adjacent to Mare Humorum. The interpretation of these data suggests that:

1. The central part of the crater, including the peak complex, may have a more mafic composition with a higher pyroxene component than surrounding highlands
2. Extensive extrusive volcanism may have occurred within the eastern portion of the floor as indicated by the suggested presence of a significant pyroxene component that correlates with photogeologically identified volcanic features
3. The western part of the crater floor, away from the geometric continuation of the western edge of Mare Humorum, is composed of highlands-rich material

This apparent dichotomy between the western and eastern side of the floor-fractured crater Gassendi may be strongly related to the early thermal history of Mare Humorum.

The crater is named after Pierre Gassendi (1592, 1655), French philosopher, scientist and mathematician. In 1631, Gassendi became the first person to observe the transit of a planet across the Sun, viewing the transit of Mercury which Kepler had predicted.