Published On: Mon, Mar 7th, 2016

Dawn’s First Year at Ceres: A Mountain Emerges

NASA Mystery Mountain Pops Up in Striking Ceres Photo

 

One year ago, on March 6, 2015, NASA’s Dawn spacecraft slid gently into orbit around Ceres, the largest body in the asteroid belt between Mars and Jupiter.  Since then, the spacecraft has delivered a wealth of images and other data that open an exciting new window to the previously unexplored dwarf planet.

“Ceres has defied our expectations and surprised us in many ways, thanks to a year’s worth of data from Dawn. We are hard at work on the mysteries the spacecraft has presented to us, ” said Carol Raymond, deputy principal investigator for the mission, based at NASA’s Jet Propulsion Laboratory, Pasadena, California.

Among Ceres’ most enigmatic features is a tall mountain the Dawn team named Ahuna Mons. This mountain appeared as a small, bright-sided bump on the surface as early as February 2015from a distance of 29, 000 miles (46, 000 kilometers), before Dawn was captured into orbit. As Dawn circled Ceres at increasingly lower altitudes, the shape of this mysterious feature began to come into focus. From afar, Ahuna Mons looked to be pyramid-shaped, but upon closer inspection, it is best described as a dome with smooth, steep walls.

Dawn’s latest images of Ahuna Mons, taken 120 times closer than in February 2015, reveal that this mountain has a lot of bright material on some of its slopes, and less on others. On its steepest side, it is about 3 miles (5 kilometers) high. The mountain has an average overall height of 2.5 miles (4 kilometers). It rises higher than Washington’s Mount Rainier and California’s Mount Whitney.

 

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Scientists are beginning to identify other features on Ceres that could be similar in nature to Ahuna Mons, but none is as tall and well-defined as this mountain.

“No one expected a mountain on Ceres, especially one like Ahuna Mons, ” said Chris Russell, Dawn’s principal investigator at the University of California, Los Angeles. “We still do not have a satisfactory model to explain how it formed.”

About 420 miles (670 kilometers) northwest of Ahuna Mons lies the now-famous Occator Crater. Before Dawn arrived at Ceres, images of the dwarf planet from NASA’s Hubble Space Telescope showed a prominent bright patch on the surface. As Dawn approached Ceres, it became clear that there were at least two spots with high reflectivity. As the resolution of images improved, Dawn revealed to its earthly followers that there are at least 10 bright spots in this crater alone, with the brightest area on the entire body located in the center of the crater. It is not yet clear whether this bright material is the same as the material found on Ahuna Mons.

 

NASA- This is actually a picture from February when Dawn was closing in on Ceres,   but it gives you a sense of what the dwarf planet is shaped like. Unlike other members of the asteroid belt,   Ceres is round -- that's what makes it a dwarf planet. You can also see some white spots on the surface that are still puzzling scientists after months of study. ANALYSIS: NASA: We Need YOUR Help to Solve Ceres Mystery While scientists were of course interested in what the pictures showed,   back then the main purpose of these shots was for "optical navigation",   according to the Dawn blog. "Just as when it reached its first deep-space target,   the fascinating protoplanet Vesta,   mission controllers have to discover the nature of the destination as they proceed,  " the blog said at the time . "They bootstrap their way in,   measuring many characteristics with increasing accuracy as they go,   including its location,   its mass and the direction of its rotation axis." NASA/JPL-CALTECH/UCLA/MPS/DLR/IDA

 

“Dawn began mapping Ceres at its lowest altitude in December, but it wasn’t until very recently that its orbital path allowed it to view Occator’s brightest area. This dwarf planet is very large and it takes a great many orbital revolutions before all of it comes into view of Dawn’s camera and other sensors, ” said Marc Rayman, Dawn’s chief engineer and mission director at JPL.

by JPL

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