Image: Science Advances: "Reorientation and despinning of 4 Vesta formed the Divalia Fossae" Authors: Dr. Hiu Ching Jupiter Cheng 1,2 , Dr. Christian Klimczak 1, Isamu Matsuyama3 1-Department of Geology, University of Georgia, Athens, GA 30602, USA. 2-Department of Geological Sciences, University of Alabama, Tuscaloosa, AL 35401, USA. 3-Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA. Abstract: Vesta, the only differentiated rocky protoplanet explored by a spacecraft, offers insight into early planetary formation. The Divalia Fossae, surface troughs comparable in size to the Grand Canyon, encircle two-thirds of the equator. Two giant impacts reshaped the southern hemisphere, where an older basin is partially superposed by the younger Rheasilvia basin. The origin of the Divalia Fossae is widely accepted as directly linked to the Rheasilvia impact, either by tectonics caused immediately by the impact, up-spinning, or secondary cratering. We present several geologic constraints that support a tectonic origin of the troughs due to the adjustment of Vesta’s spin axis to a geoid changed by both large impacts. The best fit to Vesta’s gravitational field corresponds to a spin axis reorientation of 3° that, when coupled with despinning, induces a stress state that predicts Divalia Fossae’s established location, fracture type, and orientation. These insights underline the importance of tectonic processes in the early evolution of protoplanets. (A) Equatorial view of Vesta showing major landforms with respect to spin axis and equator. (B) Vesta’s southern hemisphere centered on the south pole. Elevations are color coded with warmer tones representing higher elevations and cooler tones representing lower elevations. The large-scale troughs, Divalia and Saturnalia Fossae, are labeled with black lines. The outlines of the Rheasilvia and Veneneia basins are marked with white lines. Three dimensional (3D) shape model is from the Vesta Trek Portal. Science Advances / 25 Jun 2025 / Vol 11, Issue 26 / DOI: 10.1126/sciadv.ads7984 Type of News/Audience: Department News Alumni News Research Areas: Planetary Geology Read More: Science Advances - AAAS
