Timescales of shock processes in martian meteorites

火星陨石冲击过程的时间尺度

• 批准号: 402260-2011
• 负责人: Walton, Erin
• 金额: $ 1.68万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=573220
• 关键词: Timescales; shock; processes; martian; meteorites

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.

目前世界上收藏的火星陨石有55块。这些陨石是通过小行星或彗星与火星表面的高速碰撞(撞击)被抛入太空的，将岩石加速到5公里/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具有独特的特征，称为冲击变质效应。我的研究重点是从冲击变质作用产生的矿物和结构中读取陨石的历史，揭示行星之间物质如何交换的重要线索。特别值得一提的是，高温和高压会导致岩石的小块熔化，称为冲击熔块。当这些熔体从高温下冷却时，矿物就会结晶。在冲击熔岩口袋中也发现了大量的火星大气，因为这种成分在撞击过程中被强迫进入岩石。 在这个项目中，将使用包括透射电子显微镜、拉曼光谱和Ar同位素年代学在内的先进分析和成像仪器来研究强烈冲击的火星玄武岩陨石-雪戈特陨石。透射电子显微镜和拉曼能够分析微米(0.001毫米)到纳米(0.000001毫米)的冲击熔融口袋中发现的矿物的成分、结构和纹理。这将告诉我们撞击过程中矿物结晶的准确温度和压力，以及压力持续了多长时间。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，我们可以预期在火星表面留下多大的陨石坑。Ar激光探测系统将被用来从冲击熔体中结晶的富K矿物中提取Ar同位素。这将使我们能够限制冲击变质作用的时间(年龄)，这一点目前尚不清楚。这项研究的第二阶段是调查陆地撞击结构中的自然冲击岩石，这些岩石可以用来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。