Saturns moon Iapetus, the Yin-and-Yang of solar system

Saturns moon Iapetus is the Yin and Yang of the solar system, with one hemisphere as white as snow, and the other as black as tar, pictures returned by the NASA/ESA/ASI Cassini mission to the ringed planet has shown.

Washington, Sept 13 : Saturn's moon Iapetus is the Yin and Yang of the solar system, with one hemisphere as white as snow, and the other as black as tar, pictures returned by the NASA/ESA/ASI Cassini mission to the ringed planet has shown.

The images show a heavily cratered surface along with a 20-kilometre high mountain ridge that runs along the moon's equator, giving the satellite a walnut-shaped appearance.

"The images are really stunning. Every new picture contained its own charm. I was most pleased about the images showing huge mountains rising over the horizon. I knew about this scenic viewing opportunity for more than seven years, and now the real images suddenly materialized," said Tilmann Denk, Cassini imaging scientist at the Free University in Berlin, Germany.

"Our flight over the surface of Iapetus was like a non-stop free fall, down the rabbit hole, directly into Wonderland! Very few places in our solar system are more bizarre than the patchwork of pitch dark and snowy bright we've seen on this moon," said Carolyn Porco, Cassini imaging team leader at the Space Science Institute, Boulder, Colorado.

This flyby was nearly 100 times closer to Iapetus than Cassini's 2004 flyby, bringing the spacecraft to about 1,640 kilometres (1,000 miles) from the surface.

The Cassini astronomers are now trying to solve the mystery behind the moon's irregular walnut shape, the mountain ridge that lies almost directly on the equator and the satellite's brightness contrast.

They said Cassini's multiple observations of Iapetus would help in characterizing the chemical composition of the surface; and for searching evidence of a faint atmosphere or erupting gas plumes.

The observations will also help in mapping the nighttime temperature of the surface, they said, adding that these and other results will be analyzed in the weeks to come.

"Iapetus provides us a window back in time, to the formation of the planets over four billion years ago. Since then its icy crust has been cold and stiff, preserving this ancient surface for our study," said Torrence Johnson, Cassini imaging team member at JPL.

Scientists said the return of images and other data got delayed early Tuesday due to a galactic cosmic ray hit, which put the spacecraft into a precautionary state called safe mode.

This occurred after the spacecraft had placed all of the flyby data on its data recorders and during the first few minutes after it began sending the data home. The data flow resumed later that day and concluded on Wednesday.

Now the spacecraft is operating normally and its instruments are expected to return to normal operations in a few days, they said.

ANI