Nasa's Dawn Spacecraft Spots Mountain on Dwarf Planet Ceres

Nasa's Dawn spacecraft that slid gently into orbit around Ceres - the largest body in the asteroid belt between Mars and Jupiter - last year has delivered a wealth of data that open a new window to the previously unexplored dwarf planet.

Among Ceres' most enigmatic features is a tall mountain that the Dawn team named Ahuna Mons.

This mountain appeared as a small, bright-sided bump on the surface from a distance of 46,000 km, before Dawn was captured into orbit.

"Ceres has defied our expectations and surprised us in many ways, thanks to a year's worth of data from Dawn. We are hard at work on the mysteries the spacecraft has presented to us," said Carol Raymond, deputy principal investigator from Nasa's Jet Propulsion Laboratory, Pasadena, California.

As Dawn circled Ceres at increasingly lower altitudes, the shape of this mysterious feature began to come into focus.

From afar, Ahuna Mons looked to be pyramid-shaped, but upon closer inspection, it is best described as a dome with smooth, steep walls, Nasa said in a statement.

Scientists are beginning to identify other features on Ceres that could be similar in nature to Ahuna Mons, but none is as tall and well-defined as this mountain.

"No one expected a mountain on Ceres, especially one like Ahuna Mons," said Chris Russell, Dawn's principal investigator. "We still do not have a satisfactory model to explain how it formed."

About 670 km northwest of Ahuna Mons lies the now-famous Occator Crater.

"This dwarf planet is very large and it takes a great many orbital revolutions before all of it comes into view of Dawn's camera and other sensors," added Marc Rayman, Dawn's chief engineer.

When it arrived at Ceres on March 6, 2015, Dawn made history as the first mission to reach a dwarf planet, and the first to orbit two distinct extraterrestrial targets. The mission conducted extensive observations of Vesta in 2011-2012.

The researchers will present new images and other insights about Ceres at the 47th Lunar and Planetary Science Conference in The Woodlands, Texas, on March 22.