Ceres’ bright spots are officially no longer a puzzle as scientists have finally nailed down what’s causing that mysterious glow that emanates from the dwarf planet. And unfortunately (or fortunately, depending on your point of view), it’s not an alien civilization. It’s something much more mundane. The glow is caused by the presence of salt.
As NPR News reports, ever since February, when NASA’s Dawn spacecraft first got an up-close-and-personal view of Ceres and sent home a picture with the unusual bright spots, the mysterious glow has captured the imagination of scientists and the public alike.
Ceres lies within the asteroid belt between Mars and Jupiter. At about 587 miles in diameter, its large size qualifies it for “dwarf planet” status, rather than simply being another asteroid. Since March of this year, the NASA spacecraft Dawn has been orbiting the planet, sending back fascinating images of the alien world; especially the famed bright spots.
There are actually several bright spots on Ceres, but the two biggest and brightest are a singular bright spot and a companion cluster of smaller, dimmer spots; both of which are located in Ceres’ Occator Crater (a 50-mile wide crater on the dwarf planet). And just what those bright spots are has been a matter of speculation; some of it scientific, (are the bright spots evidence of volcanoes? ice?), and much of it harebrained (an alien civilization?).
At the time, according to an NPR News report, lead investigator Andreas Nathues of the Max Planck Institute for Solar System Research in Gottingen, Germany admitted that he was just as baffled by the bright spots as anyone else.
“The brightest spot continues to be too small to resolve with our camera, but despite its size it is brighter than anything else on Ceres. This is truly unexpected and still a mystery to us.”
Now that scientists have had a few months to crunch the numbers and look at the data, the bright spots are no longer a mystery. In a study published today in the journal Nature, the authors reveal that the bright spots are caused by salt.
“These unusual areas are consistent with hydrated magnesium sulfates mixed with dark background material, although other compositions are possible.”
To be clear, the term “salt” in chemistry doesn’t necessarily refer to what we think of as “salt;” that is, sodium chloride, or table salt. A variety of chemical compositions can be referred to as “salts,” due to chemical reactions and other properties. Sodium chloride is one of many.
The type of salt that’s causing the Ceres bright spots is called by hydrated magnesium sulfate, which sounds exotic, but this salt has a chemical cousin that you probably have in your medicine cabinet called Epsom Salt.
Just because the mystery of the Ceres bright spots has been solved, the dwarf planet still offers other, deeper mysteries still to be solved. Of most concern to NASA is whether the dwarf planet has water, and the signs are pointing in that direction.
“Ceres has more in common with Earth and Mars than its rocky neighbors. There are signs that Ceres contains large amounts of water ice beneath its surface. Scientists using the Herschel Space Observatory found evidence for water vapor on Ceres. The vapor may be produced by cryovolcanoes or by ice near the surface sublimating (transforming from solid to gas). This proves that Ceres has a icy surface and an atmosphere as well. Astronomers estimate that if Ceres were composed of 25 percent water, it may have more water than all the fresh water on Earth.”
NASA’s Dawn mission will continue orbiting Ceres and send back data about the bright spots and other features for the next several months.
[Photo courtesy of NASA/JPL via Wikimedia Commons | Cropped and Resized | Public Domain]