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UID:125@osups.universite-paris-saclay.fr
DTSTART;TZID=Europe/Paris:20261119T110000
DTEND;TZID=Europe/Paris:20261119T120000
DTSTAMP:20261103T175852Z
URL:https://osups.universite-paris-saclay.fr/calendrier/volatiles-under-sh
 ock-insights-from-asteroids-and-mars/
SUMMARY:Volatiles Under Shock: Insights from Asteroids and Mars
DESCRIPTION:Par Elena Dobrica\n\n\n\nAbstract\n\nVolatile-bearing minerals 
 in meteorites preserve chemical and isotopic records of geological process
 es that have shaped asteroids and planets. However\, these records can be 
 modified by subsequent impact-induced metamorphism\, complicating interpre
 tations of planetary volatile reservoirs. Although shock metamorphism is w
 idespread in planetary materials\, its effects on volatile distributions a
 nd isotopic compositions remain poorly constrained\, particularly in miner
 als that retain their crystalline structure. In this seminar\, I investiga
 te the effects of shock metamorphism on volatile-bearing minerals from ast
 eroids and Mars by combining scanning and transmission electron microscopy
  with chemical and isotopic analyses. I first examine carbonates in CM car
 bonaceous chondrites\, where nanoscale deformation microstructures reveal 
 shock histories that are not adequately captured by conventional petrograp
 hic classifications. I then investigate phosphates in ordinary chondrites 
 and samples returned from asteroid Itokawa\, showing how shock deformation
 \, localized melting\, and thermal overprinting produce heterogeneous micr
 ostructural and chemical modifications. These observations indicate that v
 olatile elements can be redistributed at the submicrometer scale without n
 ecessarily being lost from the mineral. Finally\, I examine apatite in the
  Martian meteorite Los Angeles\, where hydrogen-isotope compositions vary 
 with deformation-related defect densities and localized melting\, despite 
 comparatively unchanged water contents. This demonstrates that substantial
  isotopic modification can occur without complete melting or recrystalliza
 tion.\n\nThese studies show that shock-induced modifications can be highly
  localized and may not be apparent from bulk chemical measurements or conv
 entional petrographic observations. Therefore\, the preservation of a mine
 ral's crystalline structure or volatile abundance does not necessarily imp
 ly preservation of its original isotopic composition. Recognizing these ef
 fects is essential for interpreting volatile records in meteorites and ret
 urned planetary samples\, and for reconstructing the evolution of volatile
  reservoirs on asteroids and Mars.\n\n\n\n\n\n\nLieu : IAS\, Bât. 121\, s
 alle 1-2-3
CATEGORIES:Séminaires
LOCATION:IAS\, Bât. 121 rue Jean Teillac\, Orsay\, 91400\, France
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=Bât. 121 rue Jean Teillac\
 , Orsay\, 91400\, France;X-APPLE-RADIUS=100;X-TITLE=IAS:geo:0,0
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DTSTART:20261025T020000
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