Iapetus gets dusted

Imagine a powdered sugar doughnut hole plowing through a cloud of dark-chocolate dust. The resulting two-colored treat would resemble one of Saturn’s weirder moons, Iapetus — an icy world with a coal-black face and a bright white backside.

For centuries astronomers have puzzled over the source of this yin-yang color pattern. Now a team led by graduate student Daniel Tamayo of Cornell offers an explanation: Dust flung from another one of Saturn’s moons is coating one side of Iapetus. Because Iapetus doesn’t rotate, the same face continually catches the dark moon flakes.

“Iapetus is probably one of the most striking bodies in the solar system, and one of the longest-standing problems in planetary science,” Tamayo says. In a study posted online July 7 in Icarus, Tamayo mathematically describes the movement of dust particles in the outer Saturnian system. He focuses on dust coming from Phoebe, a dark and distant, irregularly shaped moon that circles Saturn in the opposite direction as Iapetus. Phoebe’s retrograde motion puts it at odds with a number of other far-flung moons.

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Scientists: Saturn moon could support life

Where there's salt, there's water and rock, it seems. And where there's water and rock, there could be life.

NASA's Saturn-exploring Cassini spacecraft has gathered new evidence that conditions on Enceladus, one of Saturn's 53 named moons, could support life, said Dr. Carolyn Porco, director of the Cassini Imaging Central Laboratory for Operations at the Space Science Institute in Boulder, Colorado.

"On Enceladus we have conditions under the surface that we know could be enjoyed by organisms similar to types of organisms we find right here on Earth," she said Friday.

Several years ago, Cassini, launched in 1997, spotted jet sprays shooting out of fissures called tiger stripes in Enceladus' southern polar region. Lighter particles from those jets provide most of the material for Saturn's outermost ring, called the E ring. But heavier particles fall back to the moon's surface, Porco explained. Cassini took measurements of the spray during three passes and found a greater concentration of sodium and potassium grains (that is, salt) nearer Enceladus' surface than farther out, according to a paper published in this week's edition of the journal Nature.

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Saturnian moon's ocean full of gas

New data from NASA's Cassini spacecraft indicates the Saturnian moon Enceladus may have a fizzy ocean capable of harbouring life.
The findings could explain the vast icy plumes of water that spray into space through fissures - known as tiger stripes - on the moon's frozen surface.
Lead Cassini planetary scientist Dr Dennis Matson from NASA's Jet Propulsion Laboratory in Pasadena California, says "geophysicists expected Enceladus to be a lump of ice, cold, dead and uninteresting".
Instead scientists have recently discovered the moon is covered with geysers shooting plumes of water vapour, icy particles and organic compounds.
Matson says many researchers viewed the icy jets as proof of a large subterranean body of water.
Pockets of liquid water with temperatures around 0°C near the surface could explain the watery plumes.
Cassini's instruments detected have carbon, hydrogen, oxygen, nitrogen, and various hydrocarbons in the plumes gas.
In 2009, the spacecraft's cosmic dust analyser found sodium and potassium salts together with carbonates locked in the plumes' icy particles, strengthening the underground ocean hypothesis.