University of Cambridge > > Occasional Earth Science Seminars > Hypervelocity impact on Earth: Cratering mechanics, shock processes and environmental consequences

Hypervelocity impact on Earth: Cratering mechanics, shock processes and environmental consequences

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Hypervelocity impact effects in our Solar System are now widely appreciated as having contributed to fundamental planet-building and planet-modifying processes throughout geological time. The strain rates at which impact events take place are exceptional relative to the timescales of most geological processes with which we are familiar. Hypervelocity impact can cause intense shock loading resulting in melting, vaporization and even plasma formation in target materials. Further from the contact and the compression locus (>50 GPa), shock waves cause local melting and solid-state phase transformations, with the creation of new structural states and mineral polymorphs. An overview will be presented with emphasis on terrestrial impact cratering. Approximately 200 impact structures are now proven on Earth, which is a shadow of its true historical record. This paucity of craters is due to Earth being an active planet and it having erased the majority of past impact evidence due to plate tectonics, volcanic activity, burial and erosion. Nevertheless, valuable examples have survived: we will tour some of them and explore the intriguing products of hypervelocity impact as we strive to understand these extreme processes. We will also consider the future and what potential threats are posed to our environment and social infrastructure by asteroids and comets colliding with Earth.

Short bio John Spray is Director of the Planetary and Space Science Centre at the University of New Brunswick. He currently manages a research team comprising research scientists, engineers, graduate and undergraduate students and staff. The team’s research activities focus on investigating planetary materials, frictional melting, impact cratering mechanics, the geology of the Moon and Mars, and processes associated with hypervelocity impact and shock effects. The latter involves developing and testing materials for their impact–resistance, of relevance to the defence, aerospace and space sectors. John Spray received his BSc in Geology from Cardiff University (Wales) and his PhD in Earth Sciences from Cambridge University (England). He joined the faculty of the University of New Brunswick in 1986 where he now holds the Canada Research Chair in Extreme Deformation and Planetary Materials. He is a co-investigator on science teams for NASA ’s Mars Science Laboratory and the European Space Agency’s ExoMars rover missions.

This talk is part of the Occasional Earth Science Seminars series.

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