The mystery of Ceres bright spots, first captured by Dawn as it neared the dwarf planet last year, may have finally been solved.

Images of Occator captured by Dawn showed shinning spots in its center that could not be readily explained. Many theories were proposed and NASA also posed the question to the world seeking answers to what those mysterious spots could be. Though it was widely accepted the spots were likely salt deposits, the chemical composition remained unclear and what caused the spots. In a new paper published in Nature, its authors claim the salts could be sodium carbonate deposits.

"Spectra of these bright areas are consistent with a large amount of sodium carbonate, constituting the most concentrated known extraterrestrial occurrence of carbonate on kilometre-wide scales in the Solar System," wrote authors of the study.

The salts were earlier thought to be magnesium sulphate. In the paper, researchers said carbonates mixed with a small amount of dark component and small amount of pollysilicates are reflecting light.

How did deposits come to be in the crater? The researchers have proposed that they could have come from within Ceres, reports The Christian Science Monitor. They also have proposed that the salts are deposits left over after crystallization of salty water. The heat for the process could have come from an impact crater.

In another study, researchers have proposed Ceres is more complex than previously thought. It was believed the planet was made of ice and rock on top of each other. The second paper suggests the planet's subsurface is not as icy as previously thought. Analysis of the deep crates on the dwarf planet has suggested the subsurface is no more than 40 percent ice with the rest being made up by rock and salts, suggesting Ceres could be a precursor planet that did not evolve into one.