Ceres, is the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter. Its diameter is approximately 945 kilometers (587 miles), making it the largest of the minor planets within the orbit of Neptune. The thirty-third-largest known body in the Solar System, it is the only one identified orbiting entirely within the orbit of Neptune that is a dwarf planet.

Composed of rock and ice, Ceres is estimated to comprise approximately one third of the mass of the entire asteroid belt. Ceres is the only object in the asteroid belt known to be rounded by its own gravity. From Earth, the apparent magnitude of Ceres ranges from 6.7 to 9.3, and hence even at its brightest, it is too dim to be seen with the naked eye, except under extremely dark skies.

Ceres was the first asteroid discovered, by Giuseppe Piazzi at Palermo on 1 January 1801. It was originally considered a planet, but was reclassified as an asteroid in the 1850s when many other objects in similar orbits were discovered. Ceres appears to be differentiated into a rocky core and icy mantle, and may have a remnant internal ocean of liquid water under the layer of ice. The surface is probably a mixture of water ice and various hydrated minerals such as carbonates and clay.

In January 2014, emissions of water vapor were detected from several regions of Ceres. This was unexpected, because large bodies in the asteroid belt do not typically emit vapor, a hallmark of comets.


The robotic NASA spacecraft Dawn entered orbit around Ceres on March 6, 2015. Pictures with a resolution previously unattained were taken during imaging sessions starting in January 2015 as Dawn approached Ceres, showing a cratered surface. Two distinct bright spots (or high-albedo features) inside a crater (different from the bright spots observed in earlier Hubble images) were seen in a February 19, 2015 image, leading to speculation about a possible cryovolcanic origin or outgassing.

On March 3, 2015, a NASA spokesperson said the spots are consistent with highly reflective materials containing ice or salts, but that cryovolcanism is unlikely. On May 11, 2015, NASA released a higher-resolution image showing that, instead of one or two spots, there are actually several. On December 9. 2015, NASA scientists reported that the bright spots on Ceres may be related to a type of salt, particularly a form of brine containing magnesium sulfate hexahydrite (MgSO46H2O); the spots were also found to be associated with ammonia-rich clays.

In October 2015, NASA released a
true color portrait of Ceres made by Dawn.

In the News ...

Dawn spies new detail in Ceres' bright spots   BBC - March 23, 2016
Now just 385km above the surface (lower than the space station is above Earth), the probe has revealed new features inside the mini-world's Occator Crater. This is the 92km-wide depression that has multiple bright spots of what are thought to be exposed salts. The new imagery reveals a dome in a smooth-walled pit in the centre-most bright area of the crater. With a resolution now of 35m per pixel, Dawn can make out numerous fractures that cut across the top and down the flanks of this dome. Very prominent cracks also surround the dome and run over the crater floor, extending to the other bright spots in Occator.

3D Ahuna Mons   APOD - March 19, 2016

Get out your red/blue glasses and gaze across Ceres at mysterious mountain Ahuna Mons. Shown in a 3D anaglyph perspective view, the mosaicked image data was captured in December of 2015, taken from the Dawn spacecraft's low-altitude mapping orbit about 385 kilometers above the surface of the dwarf planet. A remarkable dome-shaped feature on Ceres, with steep, smooth sides Ahuna Mons is about 20 kilometers (12 miles) in diameter at its base, rising on average 4 kilometers to a flattened summit. Similar in size to mountains found on planet Earth, no other Cerean surface feature is so tall and well-defined. It is not known what process shaped the lonely Ahuna Mons, or if the bright material streaking its steepest side is the same material responsible for Ceres' famous bright spots.

The Ceres mystery deepens: Enigmatic spots on the dwarf planet brighten and fade during the day in random, bizarre patterns   Daily Mail - March 16, 2015
For more than a year, the bright spots on Ceres (pictured) have baffled and fascinated astronomers. Theories range from salt deposits, ice and flashes of light made by aliens. Now, researchers claim the spots are more intriguing than first thought after they discovered they brighten and fade during the day, and do so randomly

Ceres' Mysterious Bright Spots Change Unexpectedly   Discovery - March 16, 2016
It''s not Dawn that has found the latest clue as to what these bright patches could be; it was a powerful observatory on Earth that noticed very slight changes as Ceres'' surface is gently heated by the sun.

The mysterious 'pyramid of Ceres' up close: Stunning new images reveal three mile high mountain has a strange 'glowing' side   Daily Mail - March 7, 2015

It is one of the many mysteries of Ceres - a gigantic pyramid in among the vast craters and alien spots. Now, Nasa has revealed stunning new close up images of the three mile high mountain Ahuna Mons. They reveal the 'pyramid' is in fact a dome with smooth, steep walls - one of which appears to glow.

Herschel Telescope Detects Water On Dwarf Planet in Asteroid Belt   Science Daily - January 22, 2014

Scientists using the Herschel space observatory have made the first definitive detection of water vapor on the largest and roundest object in the asteroid belt, Ceres. Plumes of water vapor are thought to shoot up periodically from Ceres when portions of its icy surface warm slightly. Ceres is classified as a dwarf planet, a solar system body bigger than an asteroid and smaller than a planet.