Abstract
Ceres is a partially differentiated dwarf planet, as confirmed by NASA’s Dawn mission. The Urvara basin (diameter ~170 km) is its third-largest impact feature, enabling insights into the cerean crust. Urvara’s geology and mineralogy suggest a potential brine layer at the crust-mantle transition. Here we report new findings that help in understanding the structure and composition of the cerean crust. These results were derived by using the highest-resolution Framing Camera images acquired by Dawn at Ceres. Unexpectedly, we found meter-scale concentrated exposures of bright material (salts) along the crater’s upper central ridge, which originate from an enormous depth, possibly from a deep-seated brine or salt reservoir. An extended resurfacing modified the southern floor ~100 Myr after crater formation (~250 Myr), long after the dissipation of the impact-generated heat. In this resurfaced area, one floor scarp shows a granular flow pattern of bright material, showing spectra consistent with the presence of organic material, the first such finding on Ceres beyond the vast Ernutet area. Our results strengthen the hypothesis that Ceres is and has been a geologically active world even in recent epochs, with salts and organic-rich material playing a major role in its evolution.
Highlights
Ceres is a partially differentiated dwarf planet, as confirmed by NASA’s Dawn mission
The Framing Camera6 (FC) imaged the cerean surface in seven colour filters and one clear filter (0.4–1.0 μm), leading to a global colour filter mapping at a pixel scale of ~140 m during the High Altitude Mapping Orbit (HAMO) and at a ~35 m pixel scale for the clear filter during the Low Altitude Mapping Orbit (LAMO)[10,11]
Detailed descriptions of the geology and mineralogy of Urvara using lower-resolution images already exist[13,14,15,16], the present paper focuses on observations of brine residues using highresolution images
Summary
Ceres is a partially differentiated dwarf planet, as confirmed by NASA’s Dawn mission. We report new findings that help in understanding the structure and composition of the cerean crust These results were derived by using the highest-resolution Framing Camera images acquired by Dawn at Ceres. An extended resurfacing modified the southern floor ~100 Myr after crater formation (~250 Myr), long after the dissipation of the impact-generated heat In this resurfaced area, one floor scarp shows a granular flow pattern of bright material, showing spectra consistent with the presence of organic material, the first such finding on Ceres beyond the vast Ernutet area. The southern floor shows an extended resurfacing of about 100 Myr after the impact (~250 Myr before today), which is long after the dissipation of the impact-generated heat In this younger area, one-floor scarp exhibits a granular bright material flow that shows spectra consistent with the presence of organic-rich material. Our results strengthen that Ceres is a geologically active world where salts and organicrich material play a major evolutional role
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