Previous theories suggested that frozen ammonium, which is stable only in the colder outer Solar System, played a role in Ceres' formation, indicating that the dwarf planet may have formed far from the Sun. However, the new study offers another possibility: the ammonium found in the crater's bright deposits could have come from Ceres' interior, brought to the surface by cryovolcanic processes.
Ceres, the largest object in the asteroid belt with a diameter of approximately 960 kilometers, has intrigued scientists due to its complex geology, which sets it apart from other asteroid belt objects. Data from NASA's Dawn probe, which orbited Ceres between 2015 and 2018, provided significant insights into Ceres' cryovolcanism. Bright salt deposits found in several impact craters are believed to be remnants of brine that seeped from beneath the surface over billions of years. The study of Consus Crater, located in Ceres' southern hemisphere, now reveals similar deposits, but with a distinct yellowish hue.
A Closer Look at Consus Crater
Consus Crater, though not particularly large at 64 kilometers in diameter, provides key clues to Ceres' geological history. Dawn's camera system, developed under the leadership of MPS, captured detailed images showing a partially eroded crater wall and a smaller, newer crater within it. The bright yellowish material is concentrated near the edge of this smaller crater and to the east of it.
Analysis of data from the camera system and the VIR spectrometer shows that the bright material in Consus Crater is rich in ammonium, a compound found in traces across Ceres. In earlier theories, the presence of ammonium was linked to the outer Solar System, where frozen ammonium remains stable over long periods. Scientists inferred that Ceres must have formed in that distant region before relocating to the asteroid belt. However, the new study establishes a connection between ammonium and the brines from Ceres' interior, raising the possibility that Ceres could have formed locally in the asteroid belt.
Ammonium from Ceres' Depths
Researchers propose that ammonium has been part of Ceres' composition since its formation. Over time, the ammonium, which did not bond with minerals in the mantle, accumulated in a brine layer between the crust and mantle. Cryovolcanic activity brought this ammonium-rich brine to the surface, where it interacted with the phyllosilicates - layered minerals similar to those found on Earth. Dr. Andreas Nathues of MPS, the lead author of the study, explains, "The minerals in Ceres' crust possibly absorbed the ammonium over many billions of years like a kind of sponge."
Ammonium concentration is likely higher in Ceres' deeper crust than near the surface. The study suggests that the small crater formed around 280 million years ago exposed material from these deeper ammonium-rich layers. The yellowish-bright material near the eastern edge of Consus Crater is likely ejecta from this impact.
"Consus Crater, at 450 million years old, is one of the oldest surviving structures on Ceres. It provides a unique window into processes that took place in Ceres' interior over billions of years," adds Dr. Ranjan Sarkar, a co-author of the study.
Research Report:For more details on the research, refer to the study published at:
Related Links
Max Planck Institute for Solar System Research
Dawn at NASA
Asteroid and Comet Mission News, Science and Technology
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