Dawn's color map of Ceres suggests it was once an active body
While establishing an orbit around Ceres on March 6 was a significant milestone for Dawn, the spacecraft was able to gather some insightful information during its initial approach to the dwarf planet. During that phase of the mission, the probe mapped the surface of the body in visible and infrared light, with the colorful new imagery suggesting that Ceres may once have been an active body.
Dawn's arrival at Ceres last month followed a seven and a half year journey that saw it study the asteroid Vesta, which, like Ceres, resides in the asteroid belt between Mars and Jupiter.
NASA used the spacecraft's visible and infrared mapping spectrometer (VIR) to examine Ceres, which is thought to be 25 percent water ice by mass. Studying the relative temperatures of surface features revealed variations in the color and morphology of the surface that suggest that the dwarf planet was once an active body.
"This dwarf planet was not just an inert rock throughout its history" said Chris Russell, principle investigator for the Dawn mission. "It was active, with processes that resulted in different materials in different regions. We are beginning to capture that diversity in our color images."
Examinations of the surface of Ceres during Dawn's approach revealed a surface with slightly fewer large craters than had been expected following observations made at Vesta. The data also shows that the bright regions on the dwarf planet's surface (which have been a source of fascination for both the public and scientific community alike) behave differently to the rest of the planet, though their origin remains unknown.
The two most visible bright spots on the dwarf planet's surface appear to exhibit a similar temperature to their surrounding regions, while another of the spots was found to be cooler than its immediate surroundings. It won't be possible to ascertain the nature of the fascinating features until Dawn moves closer to Ceres in the coming months.
The spacecraft will begin making observations from a distance of 8,400 miles (13,500 km) on April 23. The probe will continue to study Ceres through June 2016.
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It was my understanding that it was expected that Ceres was once molten, at least in the core. In the early solar system there were some short lived isotopes that became incorporated into small objects like Ceres. As these decayed enough heat was generated to melt these objects. Iron and Nickel and affiliated elements sank to the core and the lighter oxide minerals floated above that. Later, these objects sometimes shattered in collisions yielding both iron rich meteorites, stony meteorites and pallasites which are presumably from the transition zone and consist of mostly iron/nickel with embedded lumps of minerals (usually olivine) within them.
Is Ceres really purple and yellow?