The cosmic puzzle presented by mysterious bright spots on the dwarf planet Ceres is slowly coming into focus in new images from NASA's Dawn spacecraft — but we still don't know what they are, astronomers admit.

The newest image released by the space agency is the clearest and closest yet of the bright spots spattered on the floor of a crater on the minor planet's surface.

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

There is still debate as to what the spots might be, with guesses ranging from ice geysers or salt deposits to volcanoes.

The answer could come soon, Rayman says.

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

The new image of the Occator crater on Ceres was captured by Dawn from just 915 miles from the dwarf planet's surface during the mission's High Altitude Mapping Orbit (HAMO) phase.

The image of the 60-mile-wide, two-mile-deep crater has a resolution of about 450 feet per pixel.

Dawn will spend the next two months mapping the entire surface of the dwarf planet six times, at a slightly different angle each time, which will allow scientists to construct 3D maps of Ceres, NASA says.

Dawn was launched in September 2007 on a mission to rendezvous with Vesta and Ceres, two of the asteroid belt's three known protoplanets.

Dawn spent 14 months orbiting Vesta, arriving there in July 2011 and departing in late 2012 for its journey to Ceres.

It arrived at the dwarf planet with its mysterious bright freckles in March 2015.

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