New high-resolution images from Ceres have allowed researchers to date its famous bright spots, providing evidence for the possibility that the dwarf planet has experienced geological activity for a long time.

According to scientists at the Max Planck Institute for Solar System Research (MPS), the bright spots of Ceres located inside the Occator crater are 4 million years old, which makes them 30 million years younger that the crater itself. The results are reported in the Astronomical Journal.

The spots are mineral salt deposits spewed out by ice volcanos, making Ceres the closest body to the Sun to show episodes of cryovolcanism. NASA’s space probe Dawn has been orbiting the dwarf planet for almost two years, and the latest images captured by the MPS Framing Cameras highlight the geology of Occator. The bright spots might have the public spotlight, but smaller craters, fractures, and avalanches contribute to the complex surface of the crater.

"In these data, the origin and evolution of the crater as it presents itself today can be read more clearly than ever before,” Andreas Nathues, lead investigator for the framing camera team, said in a statement.

The age is determined by estimating the number of craters a certain region has, which is achieved using statistical analysis to work out how many impacts a body like Ceres – the largest object in the asteroid belt – should have over a certain period of time.

^{Zoomed-in image of Cerealia Facula, the main bright spot. NASA/JPL-Caltech/UCLA/MPS/DLR/IDA}

The central bright spot, technically called Cerealia Facula, is a dome 400 meters high (1,300 feet) and 3 kilometers (1.86 miles) across. Its surface displays prominent fractures and very few craters, allowing for the precise measurements. The original impact 34 million years ago allowed for these salts to move closer to the surface and escape through fissures, but it wasn’t a one off.

"The age and appearance of the material surrounding the bright dome indicate that Cerealia Facula was formed by a recurring, eruptive process, which also hurled material into more outward regions of the central pit," Nathues added. "A single eruptive event is rather unlikely."

Long-lasting events give credence to the idea that low-levels of cryovolcanism are still happening today. There are a few images, snapped at a very low angle, that suggest haze forming at the bottom of the crater, which might be related to this geological activity.

Dawn will continue to study Ceres and hopefully provide more data for astronomers to pour over. Perhaps in time we’ll find out what the dwarf planet is hiding inside.