High Resoluton Examination of the Intact "Microfossil" - Mineral Interface of ALH84001 for Evidence of Physical and Mineralogical Changes Consistent with Microbial Activity

火星-岩石特别研究机会活动的这一奖项支持威斯康星大学麦迪逊分校地质系的William W.Barker博士和Jillian F.Banfield博士对微生物活动的矿物学效应的调查。该项目由极地计划办公室、化学部和MPS多学科活动办公室资助。火星陨石ALH84001将被检查以寻找生物地球化学硅酸盐矿物蚀变的矿物学和质地证据。这项研究的具体目标是(1)通过仔细检查亚微观数量的水化产物(如粘土)的表面，寻找低温含水流体与矿物表面长期相互作用的证据；以及(2)检查“纳米化石”与下面矿物之间的界面结构，以寻找聚合物介导的粘土形成的证据，由于接触代谢副产品而产生的溶解特征，以及由于与生物聚合物的存在相关的元素浓度而产生的化学特征。将使用离子研磨和超显微陨石样品的高分辨率透射电子显微镜(HRTEM)和能量过滤透射电子显微镜(EFTEM)来检查裂隙表面的矿物，以寻找低温蚀变的证据。将使用高分辨率扫描电子显微镜(HRSEM)和其他能够分辨到原子水平的现代显微镜技术收集更多信息。这些方法将使在“微化石”和下伏基质之间的界面上的带的结构、成分和矿物学的检查成为可能。如果ALH84001含有生活在矿物表面附近的微生物，那么它们相互作用的细微尺度证据可能会保存在微生物-矿物界面上。将使用先进的物理和化学方法来检测矿物表面的变化。矿物-有机体相互作用的陆地模型将被用来区分生物和无机中介的改变，作为评估早期火星生命证据的一种手段。

This award in the Mars-Rock Special Research Opportunity activity supports investigation of mineralogical effects of microbial activity by Drs. William W. Barker and Jillian F. Banfield of the Geology Department, University of Wisconsin-Madison. The project is funded by the Office of Polar Programs, the Chemistry Division, and the MPS Office of Multidisciplinary Activities. Martian meteorite ALH84001 will be examined for mineralogical and textural evidence of biogeochemical silicate mineral alteration. The specific goals of the research are (1) to search for evidence of long-term interaction between low-temperature hydrous fluids and mineral surfaces by careful examination of surfaces for submicroscopic quantities of hydration products, such as clays; and (2) to examine the structure of the interface between the `nanofossils` and underlying minerals for evidence of polymer-mediated clay formation, dissolution features due to exposure to metabolic byproducts, and chemical signatures due to elemental concentrations associated with the presence of biopolymers. High resolution transmission electron microscopy (HRTEM) and energy-filtered transmission electron microscopy (EFTEM) of ion milled and ultramicrotomed meteorite samples will be used to examine the minerals at the crack surface for evidence of low-temperature alteration. Additional information will be gathered using high-resolution scaning electron microscopy (HRSEM) and other modern microscopy techniques capable of resolution to the atomic level. These methods will enable examination of the structure, composition, and mineralogy of the zone at the interface between the `microfossils` and underlying substrate. If ALH84001 contained microbes that lived in proximity to mineral surfaces, fine scale evidence for their interactions may be preserved at the microbe-mineral interface. Advanced physical and chemical methods will be used to detect alteration of the mineral surface. Terrestrial models for mineral-organism interaction will be used to distinguish biologically from inorganically-mediated alteration as a means of evaluating evidence of early Martian life.