Closing in on Ceres

Ceres is our solar system's largest asteroid - a strange celestial body that researchers know hardly anything about. With a diameter of 950 kilometers (590 miles) and its almost globe-like shape, it more closely resembles a planet rather than the much smaller, irregularly shaped rock asteroids in the same vicinity.

Ceres moves along a trajectory more than 413 million kilometers (257 million miles) from the sun. It's far beyond the "freezing border" between Mars and Jupiter. Beyond this line, the sun's rays are so weak that water is frozen into ice.

Researchers assume that Ceres was growing into a planet roughly 4.5 billion years ago. But then it appeared to get stuck it its development. This means an earlier stage of our solar system is preserved in Ceres' ice - comparable to a mammoth frozen in ice.

First insights

At roughly 2 grams per cubic centimeter, the far-off asteroid's mass is far too low for it to be made entirely of rock. Researchers believe that under Ceres' solid crust, there's several-hundred-meter-thick layer of frozen or even liquid water.

The space telescope Herschel discovered initial evidence for this, and detailed photos are hoped to help solve the water mystery in the coming weeks. "As soon as the craters on Ceres are more clearly visible, their shape could help us deduce whether there's ice on the asteroid," said Andreas Nathues of the Max Planck Institute for Solar System Research, and astronomer and head scientist of the telescope's camera system.

Researchers in the German town of Göttingen running the instrument evaluate scientific data it yields. Scientists at the German Aerospace Center's Institute for Planetary Research in Berlin turn the photos into three-dimensional models. Researchers can then use these models to reconstruct Ceres' historical development, and try to find out which processes shaped the asteroid.

Revealing secrets

Promising crater landscapes can be seen in the new pictures that NASA's space probe Dawn sent to Earth on February 19. There small, rather shallow craters also deep impact holes, with mountains at the center. Experts estimate that some of the craters could very well have a diameter of 300 kilometers (186 miles).

With three research instruments onboard, Dawn is supposed to enter the orbit of mysterious Ceres on March 6, 2015. It will circle the dwarf planet until 2016, getting ever closer in the process.

"Mission Dawn will help us understand how water-rich asteroids were created, and how they can still be active today," explained Chris Russel, the mission's head, from the University of California in Los Angeles. And the German camera system will play an important role in that.