We Finally Know What's Causing Ceres's White Spots

Wednesday, 09 December 2015 - 1:42PM
NASA
Astronomy
Wednesday, 09 December 2015 - 1:42PM
We Finally Know What's Causing Ceres's White Spots
Ceres's white spots have been one of the biggest scientific mysteries in recent memory, with speculated causes ranging from water ice to salt deposits to aliens (not because there's any evidence of that, just because people always think it's aliens). Now, scientists believe that they have finally found the definitive answer, and it's essentially a composite of all of the most plausible explanations we've heard so far.

According to a new study published in Nature, the white spots mostly consist of salt deposits, hydrated magnesium sulfate to be exact, with some water ice scattered throughout. This makes sense, considering that water ice was the prevailing theory at first, and then the salt deposit explanation was favored more recently.

Opening quote
"The main problem we had [analyzing the bright spots] during approach phase was that our spatial resolution was too low," study leader Andreas Nathues of the Max Planck Institute told Gizmodo. "The bright spots were completely saturated," he said. "In June, we divided our exposure times for the bright spots and the dark surface. Then the spatial resolution started to become sufficient to identify what the spots are."
Closing quote

Using this new technique, the team took high-resolution images of Ceres's surface, which revealed over 130 glowing white spots, usually residing in the dwarf planet's craters. The salt could be detected by measuring the brightness of the spots, while the presence of water was gleaned from the presence of afternoon haze above the bright spots, which was determined by the Herschel Space Observatory to be water vapor.

Opening quote
"What we found is if we had very oblique views-if Ceres was located between the Sun and the spacecraft-there was an additional brightness on top of the general brightness of the bright spots," Nathues said. "This brightness exists only during the daytime, like haze on Earth. This was a surprise."
Closing quote

Since the bright spots are generally found in impact craters, the researchers suspect that the two substances come from a briny ice sheet located just below Ceres's surface, which creates surface deposits when Ceres experiences a collision with another planetary body, like an asteroid.

Opening quote
"The simplest scenario is that the sublimation process of water ice starts after a mixture of ice and salt minerals is exposed by an impact, which penetrates the insulating dark upper crust," the researchers wrote.
Closing quote

Not only does this study answer the burning questions scientists (and the rest of us) have been asking for many months now, it may shed more light on the nature of objects within the asteroid belt.

Opening quote
"Twenty years ago, we always thought asteroids and comets are different kinds of objects," Nathues said. "The picture was, asteroids are stony objects, comets are from the outer solar system and have a lot of volatile materials. Now, we know there is a continuum."
Closing quote

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