Tectonism and magmatism identified on asteroids

Abstract

Abstract Linear features generally accepted as tectonic structures have been observed on several asteroids and their presence has implications for the internal structure, strength and evolution of these various bodies. Lineaments observed on the Martian moon Phobos led to the prediction that other cratered small bodies would be similarly lineated. Observations of several small bodies, including Gaspra, Ida, Mathilde, Eros, Itokawa, Steins, Lutetia and Vesta, have identified different physical mechanisms by which linear features can be formed. Analysis shows that asteroid lineaments appear to have different origins, including impact, and that lineament orientations and magnitudes provide important constraints on the interior structure of these bodies. Being a differentiated proto-planet, Vesta is a unique body with which to study the role that internal rheologies and structures play on surface tectonic expression. Vesta presents fractures and grooves similar to the other observed asteroids, but also large-scale graben and trough structures more characteristic of terrestrial planet tectonics. Unlike many terrestrial planets, Vesta's main stressors have, however, been primarily exogenic (e.g. impacts) rather than internally driven. Nevertheless, while the search for volcanic features on Vesta has not been successful, the evaluation of the Brumalia Tholus feature suggests that the geological history of Vesta may have included magmatism.