Two unidentified bright regions have been spotted on the dwarf planet Ceres, located in the main asteroid belt between Mars and Jupiter. And now it turns out that the mystery spots are not alike.
Since March, NASA’s Dawn spacecraft has been orbiting Ceres, which scientists think is 25 percent water ice by mass. Researchers analyzing images taken during Dawn’s initial approach (before being captured into orbit) have just released a new enhanced-color map that reveals the diversity of the surface. As expected, its surface is heavily cratered—but there are fewer large craters than we thought.
Variation (however subtle) in morphology and color across Ceres’ surface suggest that it was once an active body. "This dwarf planet was not just an inert rock throughout its history. It was active, with processes that resulted in different materials in different regions,” Chris Russell from the University of California, Los Angeles, says in a news release. “We are beginning to capture that diversity in our color images.”
Years ago, researchers using NASA's Hubble Space Telescope identified several bright regions on Ceres’ surface, and Dawn is now providing a much closer look. While the source of the bright spots are still unknown, Dawn’s visible and infrared mapping spectrometer (VIR) has been examining the relative temperatures of the features on Ceres’ surface. Preliminary examination suggests that different bright regions on the surface are behaving differently, according to Federico Tosi of the Italian National Institute for Astrophysics in Rome.
A pair of neighboring spots—by far the brightest visible marks on the planetary body—are located in a crater that’s 92 kilometers (57 miles) wide. They’re situated in a region labeled “5” (pictured at the top, second row) that’s similar in temperature to its surroundings. There’s a different bright feature that corresponds to a region labeled “1” (pictured at the top, first row) that’s cooler than the rest of the dwarf planet’s surface.
While both spots 1 and 5 show up in visible light images, the latter doesn’t show up in infrared images. (The infrared images are the rightmost in the two rows pictured at the top.) "Spot number five shows no distinct thermal behavior," Tosi tells New Scientist. It’s possible that they just don’t have enough resolution yet, Nature explains.
They hope to have more details after Dawn begins its first intensive science phase, later this month, at a distance of 13,500 kilometers (8,400 miles) from the surface. The spacecraft will be studying Ceres through June 2016.
The findings were presented at the 2015 General Assembly of the European Geosciences Union in Vienna this week.