Ceres' bright spots in sharp detail

Occator is about 90km across: This is a composite of exposures to handle the differences in surface brightness

The US space agency's Dawn satellite has returned its best view yet of the enigmatic bright spots on the dwarf planet Ceres.

The features sit inside a crater called Occator, and the new image reveals their structure in very fine detail.

To produce the picture, scientists have had to combine two separate exposures: one for the bright spots and one for the darker, surrounding terrain.

From an orbital altitude of 1,470km, Dawn sees 140m in every pixel.

But the mission team is still not ready to come forward with an explanation for the spots, with ideas variously floated that they might incorporate significant quantities of ice or salt.

"Dawn has transformed what was so recently a few bright dots into a complex and beautiful, gleaming landscape," Marc Rayman, Dawn's chief engineer and mission director, said in a Nasa release.

"Soon, the scientific analysis will reveal the geological and chemical nature of this mysterious and mesmerising extraterrestrial scenery."

Dawn arrived at Ceres in March this year, and has steadily lowered its orbit since.

The pictures it is returning now are nearly 10 times better than the initial observations.

With a diameter of 950km, Ceres is the largest object in the asteroid belt between Mars and Jupiter.

[e-mail] and follow me on Twitter: @BBCAmos