Volume 128, Issue 3 e2022JE007473
Research Article

Secondary Cratering From Rheasilvia as the Possible Origin of Vesta's Equatorial Troughs

Naoyuki Hirata

Corresponding Author

Naoyuki Hirata

Graduate School of Science, Kobe University, Kobe, Japan

Correspondence to:

N. Hirata,

[email protected]

Contribution: Conceptualization, Methodology, Software, Validation, Formal analysis, ​Investigation, Resources, Data curation, Writing - original draft, Writing - review & editing, Visualization, Supervision, Project administration, Funding acquisition

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First published: 16 March 2023

Abstract

Asteroid 4 Vesta has a set of parallel troughs aligned with its equator. Although previous evaluations suggest that it is of shock fracturing tectonic origin, we propose that the equatorial troughs can be created by secondary cratering from the largest impact basin, Rheasilvia. We calculated the trajectories of ejecta particles from Rheasilvia by considering Vesta's rapid rotation. As a result, we found that secondary craters should be parallel to the latitude. In particular, if we assume that ejecta particles are launched at an initial launch velocity of approximately 350–380 m/s and a launch angle of 25°, the parallel equatorial troughs, the Divalia Fossae, can be suitably explained by secondary cratering. This model works well on objects, such as Haumea, Salacia, and Chariklo, but not on Mercury, the Moon, and regular satellites.

Key Points

  • We propose a new mechanism for the formation of equatorial troughs on Vesta

  • We calculated the distribution of ejecta particles launched from Rheasilvia

  • We found that secondary cratering from Rheasilvia matches with the equatorial troughs

Plain Language Summary

Asteroid 4 Vesta has a set of parallel troughs aligned with its equator. We propose that the equatorial troughs can be created by secondary cratering from Rheasilvia, the largest impact basin of Vesta. We calculated the trajectories of ejecta particles from Rheasilvia by considering Vesta's rapid rotation. As a result, we found that secondary craters should be parallel to the latitude. In particular, the pattern of troughs indicates that ejecta particles were launched at an initial launch velocity of approximately 350–380 m/s and a launch angle of 25°.

Data Availability Statement

The software for calculating ejecta trajectories from Rheasilvia is available at Zenodo (https://doi.org/10.5281/zenodo.7700522).