Timescales of shock processes in martian meteorites

目前，世界上共有55颗火星陨石。这些陨石是由小行星或彗星与火星表面的高速碰撞（撞击）而喷射到太空中的，将岩石加速到>5 km/s的速度。在撞击事件中产生的极端物理条件导致目标岩石的独特特征，称为冲击变质效应。我的研究重点是阅读陨石的历史从矿物和纹理产生的冲击变质，揭示重要线索的物质是如何交换行星之间。特别是，高温和高压导致岩石的小口袋变成熔融，称为冲击熔融袋。当这些熔化物从高温中冷却时，矿物结晶。大量的火星大气也被发现在冲击熔融袋中，因为这种成分在撞击过程中被迫进入岩石。 在这个项目中，将使用先进的分析和成像仪器，包括透射电子显微镜（TEM），拉曼光谱和氩同位素地质年代学，对强烈冲击的火星玄武岩陨石进行研究。TEM和拉曼能够分析在微米（0.001 mm）至纳米（0.000001 mm）尺度下的冲击熔体袋中发现的矿物的组成、结构和纹理。这将告诉我们撞击过程中矿物结晶的确切温度和压力，以及压力持续了多久。反过来，这些数据告诉我们撞击火星表面的小行星或彗星有多大，以及我们可以预期在火星表面留下多大的陨石坑。氩激光探针系统将用于从在冲击熔体中结晶的富钾矿物中提取氩同位素。这将使我们能够限制目前未知的冲击变质作用的时间（年龄）。这项研究的第二阶段是调查地球撞击结构中的自然冲击岩石，这些岩石可用于更好地了解对火星的影响。 NSERC的资金将在未来五年内支持四名研究生和五名本科生的学生研究项目。

There are currently 55 Martian meteorites in the world's collection. These meteorites were ejected into space by high-velocity collisions (impacts) of asteroids or comets with the surface of Mars, accelerating rocks to velocities >5 km/s. The extreme physical conditions produced during the impact events cause unique features in the target rocks, called shock metamorphic effects. My research focuses on reading the history of the meteorites from the minerals and textures produced by shock metamorphism, revealing important clues about how material is exchanged between planets. In particular, high temperatures and pressures cause small pockets of the rock to become molten, called shock melt pockets. Minerals crystallize as these melts cool from high temperatures. Large amounts of Martian atmosphere are also found in the shock melt pockets, as this component is forced into the rock during impact. In this project strongly shocked Martian basaltic meteorites called shergottites will be investigated using advanced analytical and imaging instrumentation including transmission electron microscopy (TEM), Raman spectroscopy and argon isotope geochronology. TEM and Raman are capable of analyzing the composition, structure and texture of minerals found in shock melt pockets at the micron (0.001 mm) to nanometer scale (0.000001 mm). This will tell us the exact temperature and pressure of mineral crystallization during impact, and also how long pressures were sustained. In turn, these data tell us how big the asteroid or comet was that hit the Martian surface and how big of a crater we can expect to be left behind on the surface of Mars. An argon laser probe system will be used to extract argon isotopes from K-rich minerals that have crystallized in the shock melts. This will enable us to constrain the timing (age) of shock metamorphism which is currently unknown. A second phase of this research is to investigate naturally shocked rocks in terrestrial impact structures that can be used to better understand impact on Mars. Funding from NSERC will support student research projects for four graduate students and five undergraduate students over the next five years.