SMALL PRINT:SATURN ISN'T short on moons: it has more than 60. And a new study of one of those moons, Dione, shows that its uppermost atmosphere contains oxygen.
The icy moon, which has a radius of about 560 kilometres, appears to have molecular oxygen ions in its “exosphere”, according to data captured by instruments aboard Nasa’s Cassini spacecraft.
“We now know that Dione, in addition to Saturn’s rings and the moon Rhea, is a source of oxygen molecules,” said Robert Tokar, a Cassini team member based at Los Alamos National Laboratory. “This shows that molecular oxygen is actually common in the Saturn system and reinforces that it can come from a process that doesn’t involve life.”
The concentration of oxygen in Dione’s atmosphere is roughly similar to what you would find in Earth’s atmosphere at an altitude of about 300 miles, he added.
“It’s not enough to sustain life, but, taken together with similar observations of other moons around Saturn and Jupiter, these are definitive examples of a process by which a lot of oxygen can be produced in icy celestial bodies that are bombarded by charged particles or photons from the Sun or whatever light source happens to be nearby.”
The information about oxygen was collected during a close pass of Cassini through the plasma wake of Dione back in April 2010, but the results were published this month in Geophysical Research Letters. “It now looks like oxygen production is a universal process wherever an icy moon is bathed in a strong trapped radiation and plasma environment,” said study co-author Andrew Coates from University College London’s Mullard Space Science Laboratory in a release. “Energetic particles hit the icy surface, the hydrogen is lost and molecular oxygen remains as an exosphere. We now know that this happens at Saturn’s moons as well as Jupiter’s – and it may well occur in extrasolar planetary systems too.”
Brainy bear takes to tools
A WILD brown bear in Alaska has been spotted indulging in what appears to be a bit of clever grooming, and it is claimed to be the first report of tool-using behaviour in the species.
A paper in Animal Cognition describes how the young bear had been feeding on a whale carcass. Another bear appeared and after some play-fighting, the second bear went to the carcass while the first bear stayed in water close to the shore.
“The animal repeatedly picked up barnacle-encrusted rocks in shallow water, manipulated and re-oriented them in its forepaws, and used them to rub its neck and muzzle. The behaviour probably served to relieve irritated skin or to remove food-remains from the fur,” writes study author Volker B Deeck. “The bear exhibited considerable motor skills when manipulating the rocks, which clearly shows that these animals possess the advanced motor learning necessary for tool-use.”
To date, primates, birds, fish and invertebrates have been seen using tools, but this is only the fifth non-primate mammal where such behaviour has been observed, according to the paper.
“While this observation of tool-use in a brown bear was documented with photographs and detailed behavioural notes as it occurred, to date, it remains an isolated incident. Dedicated research is therefore ultimately required to determine how widespread stone-rubbing and other tool-using behaviours are in this species.”
