Sponge-like moon
Thursday, 05, Jul 2007 05:05
New images of Hyperion, Saturn's largest irregularly shaped moon, have shown it to have a "sponge-like appearance".
After flybys from the Nasa Cassini vessel, a new report from Peter Thomas and his team published in the journal Nature has heralded the images as showing new details previously not picked up.
Mr Thomas' report said: "The most striking visual aspect of Hyperion is its sponge-like appearance which is unlike that of any other object imaged to date and was not suggested in the low-resolution Voyager images."
The research team noted that from calculating Hyperion's size and mass, its porosity was 40 per cent, therefore explaining why the craters which give the moon its appearance are so well preserved.
According to the report, the high porosity minimises the "amount of ejecta [debris from the formation of a crater] produced or retained".
Hyperion is mainly formed of water ice and has a similar density to that seen on other satellites orbiting close to Saturn's rings.
It orbits the planet every 21.3 days and the Nasa craft flew past the moon four times in 2005 and 2006 at a range of less than 300,000 km.
A second study headed by Dale Cruikshank has suggested that the dark material at the bottom of each crater is similar to a substance on the surface of two of Saturn's other moons: Iapetus and Phoebe.
It concludes that Hyperion's colour and reflectance can "be matched with a linear combination of water ice and the material of low albedo [something which reflects light] and red colour found on the leading hemisphere of Iapetus".
Mr Thomas is from the Cornell University centre for radiophysics and space research, while Mr Cruikshank is from the Nasa Ames research centre in California.