Alright! Now we’re getting somewhere. The Dawn spacecraft – which has now completed its first mapping orbit around the dwarf planet Ceres – acquired these closest-yet images of the mysterious bright spots on Ceres, known as Spot 5, on May 3 and 4, 2015. The distance from Ceres was 8,400 miles (13,600 kilometers). In this view, the brightest spots within a crater in Ceres’ northern hemisphere are revealed to be composed of many smaller spots. As of now, their exact nature remains unknown.
Christopher Russell, principal investigator for the Dawn mission from the University of California, Los Angeles said in a statement from NASA:
Dawn scientists can now conclude that the intense brightness of these spots is due to the reflection of sunlight by highly reflective material on the surface, possibly ice.
There have been suggestions that Spot 5 and the other bright spots on Ceres are icy plumes – or other signs of active ice – on the surface of this little world.
NASA also released a new animation of the bright spots on Ceres, which you can see here.
Dawn has now concluded its first mapping orbit, in which it completed one 15-day full circle around Ceres. During this time, Dawn made many new observations with its scientific instruments.
On May 9, the spacecraft powered on its ion engine to begin the month-long descent toward its second mapping orbit. It’ll enter the new orbit on June 6. In this next phase, Dawn will circle Ceres about every three days at an altitude of 2,700 miles (4,400 kilometers) – three times closer than the previous orbit. During this phase, referred to as Dawn’s survey orbit, the spacecraft will comprehensively map Ceres’ surface.
It’s during this coming phase of the Dawn mission that Ceres’ geologic history is expected to be revealed in more details. Scientists will also assess whether the dwarf planet is active.
The spacecraft will pause twice between now and June 6, to take images of Ceres as it spirals down into its new orbit.
Bottom line: Mysterious Spot 5 – the most prominent of Ceres’ bright spots – is shown in a new image from the orbiting Dawn spacecraft to consist of many smaller spots. Scientists still don’t know what the spots are, but they suspect the reflection of sunlight off ice, possibly active ice, on Ceres.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.