It may not be the biggest crater on dwarf planet Ceres' surface, but it's certainly one of the most compelling.
Though attention is usually focused on the small world's 57 mile (92 kilometer) wide Occator Crater that contains possible signs of an ice, or "cryo-", volcano in its center, the 21 mile (34 kilometer) wide Haulani Crater is revealing that not all impact craters are circular. This crater is doing its own thing, sporting a rather compelling polygonal shape.
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Also, it appears Haulani is a comparatively young crater that exhibits landslides down its rims and freshly excavated material from below the surface, factors that will be important when studying Ceres' composition.
"Haulani perfectly displays the properties we would expect from a fresh impact into the surface of Ceres," said Martin Hoffmann, co-investigator on the Dawn framing camera team, of the Max Planck Institute for Solar System Research, Göttingen, Germany. "The crater floor is largely free of impacts, and it contrasts sharply in color from older parts of the surface."
But what's its polygonal shape about? Well, it looks like Haulani it telling us something about Ceres' internal structure. According to Dawn mission scientists, the straight edges seen along Haulani's rim and other Cerean craters revel pre-existing faults and stresses in the crust.
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This highly detailed image of Haulani comes as NASA's Dawn probe continues its in-depth study of Ceres in its lowest mapping orbit, skimming above the surface at an altitude of only 240 miles (385 kilometers).
Planetary scientists have also taken an interest in Oxo crater, a feature a NASA news release refers to as a "hidden treasure". It may be only 6 miles (10 kilometers) across, but it is the brightest feature on Ceres after Occator's mysterious bright spots. Oxo is also revealing something interesting about Ceres' sub-surface. On one of its sides, material has slumped below the surface, indicating there's deep fractures and possibly caverns where the material has slumped into.
"Little Oxo may be poised to make a big contribution to understanding the upper crust of Ceres," said Chris Russell, Dawn mission principal investigator, of the University of California, Los Angeles.
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Dawn will complete its mission in Ceres orbit, returning valuable science data for months to come. It arrived at Ceres on March 6, 2015, after spending 14 months in orbit around massive asteroid Vesta in 2011 and 2012. By studying two objects in the asteroid belt, Dawn can compare the nature of two very different rocky bodies, revealing some of the deepest secrets of our solar system's history. By acquiring highly-detailed observations of these peculiar worlds, we can read them like an open book, showing us not only how the asteroid belt came to be, but also how planets are formed.