* Astronomy

This image of crater Dominici was taken by the Narrow Angle Camera (NAC) and Wide Angle Camera (WAC) of the Mercury Dual Imaging System (MDIS) aboard the MESSENGER spaceprobe on the 8th October, 2008.
The image shows the 20-kilometre-wide bright rayed crater Dominici. The bright rays indicate that it is relatively young. Dominici lies within a much larger impact structure, the 314-kilometre-wide Homer basin, (indicated by the blue circle in the right-hand image). The crater is named in honour of the Maltese sculptor and painter Suor Maria de Dominici (1645-1703). The nearby Titian crater (indicated by the blue arrow), shows excavated material from beneath Mercury's surface that differs in composition from the surrounding surface.

Expand (268kb, 1292 x 1200)

Expand (241kb, 1178 x 1200)

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/U. S. Geological Survey/Arizona State University

The resolution is 500 metres/pixel.
Impact craters and basins on Mercury are named after deceased artists, musicians, painters, and authors who have made outstanding contributions to their fields.

Title: Core-mantle interactions for Mercury
Authors: B. Noyelles, J. Dufey, A. Lemaitre
(Version v3)

Mercury is the target of two space missions: MESSENGER (NASA) which orbit insertion is planned for March 2011, and ESA/JAXA BepiColombo, that should be launched in 2014. Their instruments will observe the surface of the planet with a high accuracy (about 1 arcsec for BepiColombo), what motivates studying its rotation. Mercury is assumed to be composed of a rigid mantle and an at least partially molten core. We here study the influence of the core-mantle interactions on the rotation perturbed by the solar gravitational interaction, by modelling the core as an ellipsoidal cavity filled with inviscid fluid of constant uniform density and vorticity. We use both analytical (Lie transforms) and numerical tools to study this rotation, with different shapes of the core. We express in particular the proper frequencies of the system, because they characterize the response of Mercury to the different solicitations, due to the orbital motion of Mercury around the Sun. We show that, contrary to its size, the shape of the core cannot be determined from observations of either longitudinal or polar motions. However, we highlight the strong influence of a resonance between the proper frequency of the core and the spin of Mercury that raises the velocity field inside the core. We show that the key parameter is the polar flattening of the core. This effect cannot be directly derived from observations of the surface of Mercury, but we cannot exclude the possibility of an indirect detection by measuring the magnetic field.

Read more (172kb, PDF)

The International Astronomical Union (IAU) approved names for 10 impact craters on Mercury, on the 13th March, 2010.


Expand (232kb, 1024 x 866)
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

This image was taken by the Narrow Angle Camera (NAC) aboard the  MESSENGER spaceprobe on the 14th January, 2008, when it was 19,700 kilometres away.
The image shows the 35-kilometre-wide crater Benoit and the 180-kilometre-wide basin Lange. Benoit is named for Rigaud Benoit, a twentieth century Haitian painter (1911-1987), and Lange is named for American photographer Dorothea Lange (1895-1965).
Lange basin appears to have been flooded by lava, leaving faint traces of a  buried inner ring.

Expand (284kb, 1018 x 1500)
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/U. S. Geological Survey/Arizona State University

The resolution is 500 metres/pixel.
Impact craters and basins on Mercury are named after deceased artists, musicians, painters, and authors who have made outstanding contributions to their fields.