A study on the origin of ammoniated phyllosilicates discovered on the dwarf planet Ceres

Occator Crater on the dwarf planet Ceres and the structure of the ammonium molecule (Image NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)
Occator Crater on the dwarf planet Ceres and the structure of the ammonium molecule (Image NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)

An article published in the journal “Nature Communications” reports a study of the origin of the ammoniated phyllosilicates present on the dwarf planet Ceres. A team of researchers conducted lab experiments based on the simulation of the Ceres environment. The results confirm the hypothesis that this dwarf planet formed in an area of ​​the solar system where ammonia ice is stable. However, they can’t rule out that it formed in the asteroid belt.

NASA’s Dawn spacecraft offered many surprises about the dwarf planet Ceres in the phase of its mission spent in its orbit. Among the discoveries, also confirmed by spectroscopic detections conducted with telescopes on Earth, there’s an abundance of ammoniated phyllosilicates, compounds linked to the evolution of Ceres, and consequently the subject of research. The problem is to understand what processes created these phyllosilicates under the conditions present on the dwarf planet, a task that is far from easy.

The best-known processes that can lead to the formation of ammoniated phyllosilicates require solutions of water and ammonia. The presence of liquid water on the dwarf planet Ceres at least in the past is another research topic, also for the discovery of various salts. However, this new study offers an alternative by describing reactions that can occur at very low temperatures, around 54 Kelvin. The products have thermal and radiation stability at much higher temperatures, which means at 300 Kelvin and thus still well below the temperature at which water is liquid, for periods of the order of half a billion years.

The considerable amount of ammonia present on the dwarf planet Ceres has led to the hypothesis that it formed in another area of ​​the solar system and then moved into the asteroid belt, probably due to the action of the gas planets’ gravity. If the origin of the ammoniated phyllosilicates proposed by this study is correct, this represents a confirmation of that hypothesis. However, it would still be insufficient to offer definitive evidence and this means that it’s still possible that Ceres formed in the asteroid belt and only later accumulated the ammonia-rich materials that are still present.

Maria Cristina De Sanctis, among the authors of this study and of previous studies about Ceres and the compounds discovered on it, explained that this experiment suggests a process that is possible not only on this dwarf planet but also on other bodies where temperatures are very low. Understanding the processes that took place or are still taking place on bodies where conditions are extreme compared to those on Earth helps to reconstruct the history of the solar system. Ceres continues to offer ideas for studies that concern in one way or another the formation and evolution of the solar system.

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