NASA JPL 2010-084 - 2010 March 11
By precisely tracking NASA's Cassini spacecraft on its low swoops over Saturn's moon Titan, scientists have determined the distribution of materials in the moon's interior. The subtle gravitational tugs they measured suggest the interior has been too cold and sluggish to split completely into separate layers of ice and rock.
The finding, to be published in the March 12 issue of the journal Science, shows how Titan evolved in a different fashion from inner planets such as Earth, or icy moons such as Jupiter's Ganymede, whose interiors have split into distinctive layers.
This artist's illustration shows the likely interior structure of Saturn's moon Titan deduced from gravity field data collected
by NASA's Cassini spacecraft. (NASA/JPL)
Revealing Titan's Interior
- Science 12 March 2010: Vol. 327. no. 5971, pp. 1338 - 1339: DOI: 10.1126/science.1186255
The interior structure and composition of solar system bodies are key to understanding their origin and evolution. Saturn's largest icy moon, Titan, and the jovian moons, Ganymede and Callisto, are of similar size, mean density, and primordial ice-rock fraction from which the satellites formed. Titan is distinct due to its dense nitrogen atmosphere, with methane as the next most abundant constituent, which precludes direct observations of the surface. Before the arrival of the Cassini-Huygens spacecraft to study the Saturn system in 2004, little was known about the nature of Titan's interior—information as to its origin, evolution, and the rate at which it degasses was limited. On page 1367 of this issue, Iess et al. (1) report evidence based on the analysis of its gravitational field that the interior was much colder than previously thought, and thereby impeded substantial melting and subsequent separation of the primordial ice-rock mixture.
Frank Sohl, Institute of Planetary Research, German Aerospace Center (DLR)