Monday, May 2, 2016

Landslides and Bright Craters on Ceres Revealed in Marvelous New Images from Dawn

Landslides and Bright Craters on Ceres Revealed in Marvelous New Images from Dawn:



Ceres' Haulani Crater, with a diameter of 21 miles (34 kilometers), shows evidence of landslides from its crater rim.  Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA


Now in orbit for just over a year at dwarf planet Ceres, NASA’s Dawn spacecraft continues to astound us with new discoveries gleaned from spectral and imagery data captured at ever decreasing orbits as well as since the probe arrived last December at the lowest altitude it will ever reach during the mission.Mission scientists have just released marvelous new images of Haulani and Oxo craters revealing landslides and mysterious slumps at several of the mysterious bright craters on Ceres - the largest asteroid in the main Asteroid Belt between Mars and Jupiter.The newly released image of oddly shaped Haulani crater above, shows the crater in enhanced color and reveals evidence of landslides emanating from its crater rim.“Rays of bluish ejected material are prominent in this image. The color blue in such views has been associated with young features on Ceres,” according to the Dawn science team.“Enhanced color allows scientists to gain insight into materials and how they relate to surface morphology.” Look at the image closely and you’ll see its actually polygonal in nature - meaning it resembles a shape made of straight lines - unlike most craters in our solar system which are nearly circular.”The straight edges of some Cerean craters, including Haulani, result from pre-existing stress patterns and faults beneath the surface,” says the science team.Haulani Crater has a diameter of 21 miles (34 kilometers) and apparently was formed by an impacting object relatively recently in geologic time and is also one of the brightest areas on Ceres.“Haulani perfectly displays the properties we would expect from a fresh impact into the surface of Ceres. The crater floor is largely free of impacts, and it contrasts sharply in color from older parts of the surface," said Martin Hoffmann, co-investigator on the Dawn framing camera team, based at the Max Planck Institute for Solar System Research, Göttingen, Germany, in a statement.The enhanced color image was created from data gathered at Dawn’s High Altitude Mapping Orbit (HAMO), while orbiting at an altitude of 915 miles (1,470 kilometers) from Ceres.Data from Dawn’s VIR instrument shows that Haulani’s surface is comprised of different materials than its surroundings."False-color images of Haulani show that material excavated by an impact is different than the general surface composition of Ceres. The diversity of materials implies either that there is a mixed layer underneath, or that the impact itself changed the properties of the materials," said Maria Cristina de Sanctis, the VIR instrument lead scientist, based at the National Institute of Astrophysics, Rome.Since mid-December, Dawn has been orbiting Ceres in its Low Altitude Mapping Orbit (LAMO), at a distance of 240 miles (385 kilometers) from Ceres, resulting in the most stunning images ever of the dwarf planet.By way of comparison the much higher resolution image of Haulani crater below, is a mosaic of views assembled from multiple images taken from LAMO at less than a third of the HAMO image distance - at only 240 miles (385 kilometers) above Ceres.Dawn has also been busy imaging Oxo Crater, which despite its small size of merely 6-mile-wide (10-kilometer-wide) actually counts as a “hidden treasure” on Ceres - because it’s the second-brightest feature on Ceres!Only the mysterious bright region comprising a multitude of spots inside Occator Crater shine more brightly on Ceres.Most importantly, Oxo Crater is the only place on Ceres where Dawn has detected water at the surface so far. Via VIR, Dawn data indicate that the water exists either in the form of ice or hydrated minerals. Scientists speculate that the water was exposed either during a landslide or an impact."Little Oxo may be poised to make a big contribution to understanding the upper crust of Ceres," said Chris Russell, principal investigator of the mission, based at the University of California, Los Angeles.The signatures of minerals detected on the floor of Oxo crater appears to be different from the rest of Ceres.Furthermore Oxo is “also unique because of the relatively large "slump" in its crater rim, where a mass of material has dropped below the surface.”Dawn is Earth’s first probe in human history to explore any dwarf planet, the first to explore Ceres up close and the first to orbit two celestial bodies.The asteroid Vesta was Dawn’s first orbital target where it conducted extensive observations of the bizarre world for over a year in 2011 and 2012.The mission is expected to last until at least later into 2016, and possibly longer, depending upon fuel reserves.Dawn will remain at its current altitude at LAMO for the rest of its mission, and indefinitely afterward, even when no further communications are possible.Stay tuned here for Ken's continuing Earth and planetary science and human spaceflight news.Ken Kremer

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