Cerealia Facula, a dome-like feature located in the center of Ceres’ Occator crater, is only 4 million years old — approximately 30 million years younger than the crater itself, according to research led by Dr. Andreas Nathues of the Max Planck Institute for Solar System Research.
Cerealia Facula, a bright dome in the center of Occator Crater on the dwarf planet Ceres, is shown in enhanced color in this view from NASA’s Dawn spacecraft. Image credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / PSI / LPI.
Occator crater is one of the largest craters on the dwarf planet Ceres. With a diameter of 57 miles (92 km), it is larger than Tycho crater on the Moon. Its steep walls stand tall at over 1.4 miles (2 km), higher than the North face of the Eiger in the Bernese Alps.
“Occator crater is located in the northern hemisphere of Ceres. In its center a pit with a diameter of about 6.8 miles (11 km) can be found. On some parts of its edges, jagged mountains and steep slopes rise up to 2,460 feet (750 m) high,” Dr. Nathues and co-authors said.
“Within the pit a bright dome formed. It is 1,312 feet (400 m) high, has a diameter of 1.9 miles (3 km), and displays prominent fractures.”
“This dome, called Cerealia Facula, contains the brightest material on Ceres.”
The researchers analyzed data from two instruments on board NASA’s Dawn spacecraft: the framing camera, and the visible and infrared spectrometer (VIR).
VIR data show that Cerealia Facula is very rich in carbonate salts.
Since later impacts in this area did not expose any other material from the depth, this feature possibly consists entirely of bright material.
The secondary, smaller bright areas of Occator, called Vinalia Faculae, are paler, form a thinner layer and — as VIR and camera data show — turn out to be a mixture of carbonates and dark surrounding material.
New evidence also suggests that Cerealia Facula likely rose in a process that took place over a long period of time, rather than forming in a single event.
Dr. Nathues and his colleagues believe the initial trigger was the impact that dug out Occator crater.
This impact happened some 34 million years ago and caused briny liquid to rise closer to the surface.
Water and dissolved gases, such as carbon dioxide and methane, came up and created a vent system. These rising gases also could have forced carbonate-rich materials to ascend toward the surface.
During this period, the bright material would have erupted through fractures, eventually forming the dome that we see today.
“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,” Dr. Nathues said.
“A single eruptive event is rather unlikely,” he added.
The findings were published in the March 2017 issue of the Astronomical Journal .
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A. Nathues et al. 2017. Evolution of Occator Crater on (1) Ceres. AJ 153 (112); doi: 10.3847/1538-3881/153/3/112
