Mysterious bright spot on the Ceres, not ice, but salt
Pseudo color image on the Ceres Occator crater, according to the different chemical composition.Photo credit: NASA/JPL - Caltech/UCLA/MPS/DLR/IDA
Using NASA's Dawn the data sent back (Dawn) detector, two new studies reveal the Ceres (Ceres) for a long time some of the hidden secret, including many scattered on the surface of the dwarf planet mystery spots actually was.
In one study, scientists determine these bright material is some kind of salt.A second study was detected clay rich in ammonia, which poses challenges to the formation of Ceres theory.
Mysterious bright spot
Ceres has more than 130 bright spot, the vast majority of related to impact craters.The Max Planck institute in Germany Andreas na, the institute of the solar system (Andreas Nathues), according to a study led by these bright material consistent with some six water magnesium sulfate.This is a different type of magnesium sulfate, similar to the Epsom salt of the earth's (Epsom salt).
He, and his colleagues studied the dawn on the camera to photograph, found that these areas are rich in salt, left over from the past after water ice sublimation.Asteroids, they say, is the mixture of ice and salt out of the grouts.
She said, "these bright spots on Ceres global distribution show that the planet's surface under a stratum containing salt water ice."
Impact craters in the fog
The study authors said that the average diameter of 940 kilometers of Ceres, the surface is mostly dark, brightness like fresh asphalt.Scattered around the Ceres, on the surface of a bright spot, brightness is varied, the most bright spots of about 50% of the sunlight.However, there is no clear to detect water ice on the Ceres.To fix this problem, need higher resolution data.
Occator crater, combined with 3 d terrain data perspective, shows the crater topography.Photo credit: NASA/JPL - Caltech/UCLA/MPS/DLR/IDA
The brightest of Ceres material in a crater called Occator inside.Occator crater diameter of 90 kilometers, it in the middle of the pit covered with bright material, about 10 km wide, about 500 meters deep.There are several dark stripes, may be a crack, crosses from the pits.Once in the middle of the 500 meters high mountain ruins can still see.
According to Occator crater steep mountain and the number of landslide debris, scientists speculate that it should be the youngest Ceres geological characteristics.Dawn mission scientists estimate that about 78 million years age.
The study authors said the Occator crater appears to show some of the photos. There were diffuse fog near the surface of the fill the bottom of the crater.Perhaps with the herschel space observatory in 2014 on the Ceres observed the discovery of water vapor.The study authors, said that fog seems to appear in the local time at noon, at dawn and at dusk can't see.This suggests that this phenomenon is similar to the activity on the surface of the comet, water vapor raise the tiny dust particles and ice particles.Data and analysis of the future may be testing this hypothesis, and reveal more clues to help scientists uncover the processes by which lead to this activity.
Dawn mission chief scientist, university of California, Los Angeles, Chris Russell (Chris Russell) said, "dawn science team is still discussing the results and analysis data, in order to better understand Occator what's happening in the crater."
At noon, Occator fog in the crater is likely to occur.The mechanism behind this phenomenon is still to be studied.Photo credit: NASA/JPL - Caltech/UCLA/MPS/DLR/IDA
The significance of ammonia
In another study, dawn science team members examined the Ceres chemical composition, found evidence of clay rich in ammonia.They used the dawn on the data from the visible light and infrared mapping spectrometer, this equipment can see how different wavelengths of light reflection in the surface of Ceres, so as to determine its mineral composition.
On today's Ceres sublimation ammonia ice itself, because the dwarf planet is too warm.However, ammonia if combined with other minerals (in the form of chemical bonds tied together), can become quite stable.
Ammonia compounds, raises the possibility that the Ceres is not originated from the asteroid belt between Mars and Jupiter, and is likely to be formed in the outer solar system.Another view is that Ceres is in the position of near modern form, is merged from the outer solar system drift over substance.So-called "the outer solar system", refers to the orbit of Neptune, near nitrogen ice can be stable in there, not too hot and sublimate to gas.
The study's lead author, Italian institute for astrophysics Maria Cristina De santis (Maria Cristina De Sanctis) said, "the presence of ammonia containing component showed that the composition of Ceres material is in the ammonia and nitrogen accumulated abundant environment. Therefore, we believe that these substances originated in the cold of the outer solar system."
Scientists will Ceres reflective spectrum, and meteorites spectral ratio, found some similarities.Specifically, they focus on comparing the carbonaceous chondrite (carbonaceous chondrites) spectrum.Scientists used to think that such carbon-rich meteorites is very similar with Ceres.However, the team found that, in the light of these rocks and Ceres all wavelengths do not fit well.Exactly speaking, the absorption spectrum of Ceres, totally different from meteorites, but consistent with the mixture of ammonia compounds, the band will not be able to use the ground telescopes.
Scientists also pointed to another is different, the carbonaceous chondrite meteorites containing 15% to 20% of the water, and Ceres water content as high as 30%.DE santis said, "Ceres may be more volatile than those meteorites contain substances, may also absorb water from the material rich in volatile matter."
The study also showed that Ceres daytime surface temperature between 180 to 240 K.The highest temperature is measured at the equator area.The study authors say, near the equator of the temperature is too high, usually cannot support is water ice on the surface Ceres exist for a long time, but the dawn of the next probe orbit will reveal more details.
Until this week, dawn has arrived in the final orbit altitude around the Ceres, about 385 km from the surface of the dwarf planet.By the middle of December, dawn will start in the orbit observation, including the resolution reached 35 meters per pixel high-definition pictures, infrared, gamma rays, and spectrum observation, and obtain high resolution gravity data.