Weird Polygonal Crater Reveals Ceres' Faults

It may not be the biggest crater on dwarf planet Ceres' surface, but it's certainly one of the most compelling.

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.

PHOTOS: Dwarf Planet's Weirdly Mysterious Surface Mapped

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.

PHOTOS: Psychedelic Landscapes of Asteroid Vesta

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.

Source: NASA/JPL-Caltech

Ceres' Haulani Crater, with a diameter of 21 miles (34 kilometers), shows evidence of landslides from its crater rim.

After spending eight months at dwarf planet Ceres, the Dawn spacecraft

is going to get a real close look at the surface

. What the heck are those bright spots seen from afar? What sort of processes sculpt its airless surface? Scientists will get a better sense of this when the spacecraft moves from its previous orbit of 915 miles (1,470 kilometers) to just 235 miles (380 kilometers). Dawn began its maneuvers on Oct. 23 and will reach the lowest orbit of its mission by mid-December.

PHOTOS: Dwarf Planet's Weirdly Mysterious Surface Mapped

The spacecraft is expected to finish its work in mid-2016, and remain in orbit as a small satellite -- an artificial moon -- of Ceres. Meanwhile, in the thousands of pictures beamed back from the mission, scientists are starting to get a sense of what the surface really looks like.

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.

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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."

We can easily see that Ceres was

smacked by meteorites at different times

. In this picture, the crater to the left has much sharper edges than the prominent crater to the right, indicating that erosion -- probably erosion from other impacts -- has worn down the older craters.

ANALYSIS: Mysterious 'Haze' Seen Above Ceres' Weird Bright Spots

A more careful look reveals that there are actually craters on TOP of craters as space rocks of various sizes, even down to the size of pebbles or dust, periodically crash into the surface of Ceres.

If you look inside craters such as this one of Dantu -- which is roughly 77 miles (124 kilometers) across --

you can start to understand the geologic history

. The small craters you see inside occurred after the bigger crater was formed. The slumping walls show that erosion has started to occur. There's a bit of white on the surface, perhaps showing something exposed from below, and a small rille in the center.

NEWS: Dawn Mission Reveals More Detail in Mysterious Ceres

This is one of the images scientists are using to get a better look at the white spots, which have been speculated to be water ice or indications of a mineral. "Occator is home to the brightest area on Ceres, which tends to appear overexposed in most images,"

NASA wrote

about this recent composite image. "This view uses a composite of two images of Occator: one using a short exposure that captures the detail in the bright spots, and one where the background surface is captured at normal exposure."

NEWS: NASA Probe Homes in on Ceres' Mysterious Bright Spots

As observers of Earth's moon know, when you start to look at an object in different lights, different features are visible. When the sun is directly overhead on the moon, the sunlight can wash-out some of the craters' sides. When it is at a steeper angle, the shadows start to show a little bit more detail. So by looking at different angles of Ceres (at different times of the day on Ceres' surface),

as this shadowy picture shows

, scientists can see a little more of its craters and its detail -- just by using simple geometry.

ANALYSIS: Ceres’ Mystery Bright Dots May Have Volcanic Origin