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SUMMARY:Hypervelocity impact on Earth:   Cratering mechanics\, shock proce
 sses and environmental consequences - Professor John G. Spray\, University
  of New Brunswick
DTSTART:20181211T120000Z
DTEND:20181211T130000Z
UID:TALK115696@talks.cam.ac.uk
CONTACT:Andy Buckley
DESCRIPTION:Hypervelocity impact effects in our Solar System are now widel
 y appreciated as having contributed to fundamental planet-building and pla
 net-modifying processes throughout geological time. The strain rates at wh
 ich impact events take place are exceptional relative to the timescales of
  most geological processes with which we are familiar. Hypervelocity impac
 t can cause intense shock loading resulting in melting\, vaporization and 
 even plasma formation in target materials. Further from the contact and th
 e compression locus (>50 GPa)\, shock waves cause local melting and solid-
 state phase transformations\, with the creation of new structural states a
 nd mineral polymorphs. An overview will be presented with emphasis on terr
 estrial impact cratering. Approximately 200 impact structures are now prov
 en on Earth\, which is a shadow of its true historical record. This paucit
 y of craters is due to Earth being an active planet and it having erased t
 he majority of past impact evidence due to plate tectonics\, volcanic acti
 vity\, burial and erosion. Nevertheless\, valuable examples have survived:
  we will tour some of them and explore the intriguing products of hypervel
 ocity impact as we strive to understand these extreme processes. We will a
 lso consider the future and what potential threats are posed to our enviro
 nment and social infrastructure by asteroids and comets colliding with Ear
 th.\n\n\nShort bio\nJohn Spray is Director of the Planetary and Space Scie
 nce Centre at the University of New Brunswick. He currently manages a rese
 arch team comprising research scientists\, engineers\, graduate and underg
 raduate students and staff.  The team’s research activities focus on inv
 estigating planetary materials\, frictional melting\, impact cratering mec
 hanics\, 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 def
 ence\, aerospace and space sectors.\nJohn Spray received his BSc in Geolog
 y from Cardiff University (Wales) and his PhD in Earth Sciences from Cambr
 idge 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 t
 eams for NASA’s Mars Science Laboratory and the European Space Agency’
 s ExoMars rover missions.\n
LOCATION: Harker 1\, Department of Earth Sciences\, Downing Street
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