An estimate of the age of the large bright spot in Occator crater on Ceres

The great bright spot at the center of Occator crater (Image NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI/LPI)
The great bright spot at the center of Occator crater (Image NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI/LPI)

An article published in the journal “Astronomical Journal” describes a study that provides a dating to the large bright spot in Occator crater on the dwarf planet Ceres. A team of researchers led by Andreas Nathues of the Max Planck Institute for Solar System Research (MPS) in Göttingen, Germany, used data collected by NASA’s Dawn space probe to analyze the interior of Occator concluding that the bright spot is 4 million years old, 30 million less of the crater.

Almost exactly two years ago, the Dawn space probe entered the dwarf planet Ceres’ orbit but even before that event the largest of the existing bright spots on its surface was sighted. It’s been the object of various specific research and according to various analyzes of data collected by Dawn it and other smaller bright spots are composed of salts.

The central area of ​​the large bright spot was called Ceralia Facula while the neighboring bright areas (on the right side in the image below) were called Vinalia Faculae. These geological structures within Occator crater were the subject of a new research to seek to understand their age and evolution. The researchers used especially data collected by two instruments aboard the Dawn space probe: the Framing Camera, and especially high-resolution photos taken during a low-altitude mapping, and the VIR spectrometer.

The spectrometric data confirm that the reflective materials in Ceralia Facula are rich in carbonates as earlier studies already claimed although the specific type of carbonate identified in those studies are not confirmed. In Vinalia Faculae there’s a thinner layer that consists of a mix of carbonate salts and dark material.

Occator crater was formed as a result of an impact about 34 million years ago. The dome of bright material is much younger because the researchers estimated that it’s 4 million years old, recent in geological terms. The estimates were made counting and measuring smaller craters based on the assumption that a surface with many craters is older than one that has fewer of them.

The characteristics of the materials around the dome indicate that Ceralia Facula was formed by a recurring eruptive process that also pushed materials in the outer regions of the central pit. These are signs of cryovolcanism that may have been caused by the impact that created Occator crater. The tectonic upheaval of the area may have allowed underground materials to emerge and gradually form the salt deposits we see today.

It’s not yet clear whether the cryovolcanic activity has stopped or is still going on at lower levels but the variation in brightness that follows a daily rhythm detected in many of the Occator crater images suggest that there may still be some kind of activity. According to the researchers it’s possible that the sublimation of the water that emerges from the fractures generate a haze that causes the variations detected.

Basically, there are more interesting information about the great bright spot in Occator crater but there are still some questions. In the coming months, the Dawn space probe will perform observations with the Sun behind it. This could allow the measurement of new details of the salt deposits’ brightness and to further improve the understanding of what happened and perhaps is still happening on Ceres.

The big bright spot at the center of Occator crater and some other smaller spots (Image NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)
The big bright spot at the center of Occator crater and some other smaller spots (Image NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

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