Nasa's Dawn Spacecraft Takes Photos of Ceres En Route to Dwarf Planet

It has an average diameter of 950km and is thought to contain a large amount of ice.

Some scientists think it is possible that the surface conceals an ocean.

"We know so much about the solar system and yet so little about dwarf planet Ceres. Now, Dawn is ready to change that," said Marc Rayman, Dawn's chief engineer and mission director at Nasa's Jet Propulsion Laboratory in Pasadena, California.

New images show the dwarf planet at 27 pixels across, about three times better than the calibration images taken in early December.

The best images of Ceres so far were taken by Nasa's Hubble Space Telescope in 2003 and 2004.

This most recent images from Dawn, taken January 13 this year at about 80 percent of Hubble resolution, were not quite as sharp.

Over the next several weeks, Dawn will deliver increasingly better images of the dwarf planet, leading up to the spacecraft's capture into orbit around Ceres on March 6.

The images will continue to improve as the spacecraft spirals closer to the surface during its 16-month study of the dwarf planet.

"Already, the (latest) images hint at first surface structures such as craters," said Andreas Nathues, lead investigator for the framing camera team at the Max Planck Institute for Solar System Research, Gottingen, Germany.

Dawn's arrival at Ceres will mark the first time a spacecraft has ever visited a dwarf planet.

The spacecraft has already delivered more than 30,000 images and many insights about Vesta, the second most massive body in the asteroid belt.