Search for copper sulfides and sulfur chemistry in the Martian crust, based on geochemical data returned by NASA's MSL rover

自2012年8月以来，美国国家航空航天局(NASA)位于火星盖尔陨石坑的MSL月球车沿导线(约18公里)(自2012年8月以来)(几乎)连续检测到铜元素，但其量化仍然存在问题。根据目前的模型，大多数地区的铜丰度为&lt；50ppm，但在某些地区可能是本底的~20倍。该项目的目标是：(A)建立铜的量化的可靠模型，(B)确定铜的寄主矿物(特别是在铜含量高的目标上)和(C)推断其可能的形成途径。这项研究将重点放在ChemCam返回的数据上，但也将使用APXS，这是火星车上的两台仪器，分别利用激光诱导击穿光谱(LIBS)和X射线荧光来推断火星表面材料的化学成分。目标(A)要求详细分析化学摄像头的两个发射带，其中最强的两条铜发射线(324.8&327.5 nm)与其他元素(特别是钛)的发射线重叠。为了实现目标(b-c)，将特别注意铜与镍、锌、S以及主要化学元素(硅、铝、钙、镁、钠、钛、钾、锰)之间的潜在相关性，这些元素的丰度在任务期间每天例行测定。铜的升高可能与硫(硫化物偏析？)并将谨慎地证明或反驳这一假设。这项研究的高级别目标是：(1)追踪铜在火星表面和内部的命运(特别是将表面的丰度与SNC陨石和BSM[块状硅酸盐火星]中的铜的丰度进行比较)；(2)说明火星硫循环的一个特定方面(火星表面数十亿年来最重要的地球化学循环)；以及(3)研究从地球上已知的成矿过程是否可能在火星上发生(可能的速度和空间规模比地球上的要小得多)。

The element copper (Cu) is being detected (almost) continuously along the traverse (~18 km, since Aug 2012) of NASA’s MSL rover in Gale crater, Mars, but its quantification remains problematic. According to the current model, Cu abundances are < 50 ppm at most places, but may be ~20 times above background in selected areas. The goals of this project are: (a) develop a solid model of Cu quantification, (b) identify the Cu-hosting minerals (especially at targets with high Cu enrichment) and (c) infer their likely pathways of formation. This study shall focus on data returned by ChemCam, but will also use APXS, - two instruments onboard the rover that utilize LIBS (Laser Induced Breakdown Spectroscopy) and x-ray fluorescence, respectively, to infer chemical composition of Martian surface material. Goal (a) requires detailed analysis of the two ChemCam emission bands where the two strongest Cu emission lines (324.8 & 327.5 nm) overlap with lines of other elements (Ti in particular). In order to achieve goals (b-c) particular attention will be given to potential correlations of Cu with Ni, Zn, S as well as major chemical elements (Si, Al, Ca, Mg, Na, Ti, K, Mn) whose abundances are routinely determined on a daily basis over the mission. Elevated Cu might be correlated with sulfur (sulfide segregation?) and care will be given to prove or disprove that hypothesis. The high-level goals of this study are: (i) track down the fate of Cu at the surface and in the interior of Mars (in particular compare surface abundances to those in SNC meteorites and BSM [Bulk Silicate Mars]), (ii) illustrate a particular aspect of the Martian sulfur cycle (the most important geochemical cycle at the Martian surface over billions of years) and (iii) address the question if ore-forming processes known from Earth might have taken place on Mars (perhaps at much smaller rate and spatial scale than on Earth).