Dawn finale gives sharpest look ever at Ceres' bright spots
Meteorologist/Science Writer
Tuesday, July 3, 2018, 6:34 PM - NASA's Dawn mission will soon come to an end, but before that happens, the spacecraft has been sending back its closest views of Ceres ever, including the sharpest details so far of the dwarf planet's bizarre bright spots.
Dwarf planet Ceres - the largest object in the asteroid belt between Mars and Jupiter - caught public attention back in 2015 when the Dawn spacecraft arrived and began snapping thousands of images of its cratered alien landscape.
One feature that was of particular interest to everyone, though, was a cluster of mysterious bright spots, first captured by the Hubble Space Telescope, and then revealed in closer and closer images by Dawn over the 3+ years of its mission.
Now, over three years into the mission, as a result of a set of extremely low orbits (which are expected to be the spacecraft's last), we have the closest images yet, taken from around 35 kilometres above the surface!
Bright mound on southwestern edge of Cerealia Facula
CLICK OR TAP TO ENLARGE! This mosaic image shows the isolated mound located in the southwestern part of Cerealia Facula, the largest, brightest and most prominent bright spot in Occator Crater, obtained by NASA's Dawn spacecraft on June 22, 2018. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Vinalia Faculae Up Close
Vinalia Faculae, the grouping of dimmer bright spots in the eastern half of Occator Crater, are shown here in close-up, in this image from June 14, 2018, revealing the intricate patterns of lighter and darker material that make up the feature. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
"Acquiring these spectacular pictures has been one of the greatest challenges in Dawn's extraordinary extraterrestrial expedition, and the results are better than we had ever hoped," Dawn’s chief engineer at JPL, Marc Rayman, said in a NASA press release. "Dawn is like a master artist, adding rich details to the otherworldly beauty in its intimate portrait of Ceres."
What are these bright spots?
Residing in an area of Ceres dubbed 'Occator Crater', these weird bright spots initially defied explanation.
Were they made of water ice, and if so, what would that mean about the formation and interior of Ceres? Were they salt deposits, and if so, what would THAT mean about Ceres? Were they actually the glass domes of an alien base (and even if that was never a serious consideration, what would it mean for us)?
The bright deposits in Occator Crater on Ceres, as imaged by NASA's Dawn spacecraft during its Low Altitude Mapping Orbit (LAMO), at roughly 385 km above the surface. The white outlines marked on the image indicate the locations of the two above images. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/Scott Sutherland
By the time we were treated to a closer look, shown in the image above, scientists with the mission had used the spacecraft's VIMS instrument (Visible and Infrared Mapping Spectrometer) to determine that they were, indeed, salt deposits - specifically sodium carbonate.
While it is very likely that these deposits were left behind behind due to the evaporation of water or sublimation of ice into space, the exact source of that water or ice is still unknown.
According to NASA:
The wealth of information contained in these images, and more that are planned in the coming weeks, will help address key, open questions about the origin of the faculae, the largest deposits of carbonates observed thus far outside Earth, and possibly Mars. In particular, scientists have been wondering how that material was exposed, either from a shallow, sub-surface reservoir of mineral-laden water, or from a deeper source of brines (liquid water enriched in salts) percolating upward through fractures.
Whichever it is, this evaporation or sublimation is likely an ongoing process, as images from the mission have revealed a very fine haze or fog lingering along the base of Occator crater at times.
Unless NASA's plans change, this newest set of elliptical orbits the spacecraft is on will be its last, as, according to Rayman, it is expected to use up the remainder of its hydrazine fuel during these operations.
To see more images from the Dawn mission, including those from these close flybys, check out NASA's Jet Propulsion Laboratory site.
