Jean-Luc Margot

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High-resolution radar images reveal near-Earth asteroid (66391) 1999 KW4 to be a binary system. The approximately 1.5-kilometer-diameter primary (Alpha) is an unconsolidated gravitational aggregate with a spin period approximately 2.8 hours, bulk density approximately 2 grams per cubic centimeter, porosity approximately 50%, and an oblate shape dominated by(More)
Radio tracking of the MESSENGER spacecraft has provided a model of Mercury's gravity field. In the northern hemisphere, several large gravity anomalies, including candidate mass concentrations (mascons), exceed 100 milli-Galileos (mgal). Mercury's northern hemisphere crust is thicker at low latitudes and thinner in the polar region and shows evidence for(More)
Shackleton crater at the Moon's south pole has been suggested as a possible site of concentrated deposits of water ice, on the basis of modelling of bi-static radar polarization properties and interpretations of earlier Earth-based radar images. This suggestion, and parallel assumptions about other topographic cold traps, is a significant element in(More)
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. [1] The recent determination of the gravity field of Mercury and new(More)
Earth-based radar observations of the spin state of Mercury at 35 epochs between 2002 and 2012 reveal that its spin axis is tilted by (2.04 ± 0.08) arcminutes with respect to the orbit normal. The direction of the tilt suggests that Mercury is in or near a Cassini state. Observed rotation rate variations clearly exhibit an 88-day libration pattern which is(More)
Three-dimensional (3-D) maps of the nearside and polar regions of the Moon can be obtained with an Earth-based radar interferometer. This paper describes the theoretical background, experimental setup, and processing techniques for a sequence of observations performed with the Goldstone Solar System Radar in 1997. These data provide radar imagery and(More)
Mercury has a near-zero obliquity, i.e. its spin axis is nearly perpendicular to its orbital plane. The value of the obliquity must be known precisely in order to constrain the size of the planet’s core within the framework suggested by Peale [Peale, S.J., 1976. Nature 262, 765–766]. Rambaux and Bois [Rambaux, N., Bois, E., 2004. Astron. Astrophys. 413,(More)
Radar ranging from Arecibo, Puerto Rico, to the 0.5-kilometer near-Earth asteroid 6489 Golevka unambiguously reveals a small nongravitational acceleration caused by the anisotropic thermal emission of absorbed sunlight. The magnitude of this perturbation, known as the Yarkovsky effect, is a function of the asteroid's mass and surface thermal(More)
Laser altimetry by the MESSENGER spacecraft has yielded a topographic model of the northern hemisphere of Mercury. The dynamic range of elevations is considerably smaller than those of Mars or the Moon. The most prominent feature is an extensive lowland at high northern latitudes that hosts the volcanic northern plains. Within this lowland is a broad(More)