Microbial Nitrate Dependent Fe2+ oxidation. A Potential Early Mars Metabolism

描述：发展微生物学和地球化学方面的技能了解热液环境中的生物地球化学循环识别火星上生命探测的潜在生物特征今天的火星表面寒冷而干燥。这些条件被认为是不适合生命生存的；然而，地质记录包含了早期火星表面确实存在液态水的证据，这表明该星球更温暖、更潮湿，更适合生命。水的持久性尚不清楚(Carr 2006)；然而，热液系统可能是由于火山系统或陨石坑而发展起来的，温暖/热水可能已经长期存在。在地球上，热液系统被认为是生命出现的合乎逻辑的候选。系统发生学证据表明，现代嗜热微生物(生活在高温下的微生物)比任何其他形式的生命都与共同的祖先关系更近(Woese等人，1990年)。因此，火星上的热液系统不可避免地成为生命探测任务的潜在目标地点。火星科学实验室(MSL)将重点放在盖尔陨石坑的宜居环境搜索上。撞击坑为生命创造了丰富的潜在栖息地。当水从地下渗出时，会出现一个温度梯度，从撞击岩石附近的高温到地表的低温。在表面，冲击湖可以持续到蒸发发生。寻找生命的证据依赖于检测生物特征。例如，微生物的活动可以影响次生矿物的形成，并增加生物必需离子的淋溶。然而，仍然有许多问题没有得到回答，例如，哪些生物特征可以用来识别热液系统中的地下活动？温度会如何影响这些生物签名？他们在火星表面的命运是什么？这项研究的目的是为火星撞击坑中的生命探测识别潜在的生物特征。具体目标是：识别热液系统中生物活动的潜在特征。这将通过培养从热液系统中分离出来的微生物并使用地球化学分析来实现。使用地球化学模型来确定温度对生物特征的影响。这将使用建模程序CHIM-XPT来完成，以确定使用环境模拟室检测火星表面生物特征的可能性。

Description:Develop skills in microbiology and geochemistryUnderstanding biogeochemical cycling in hydrothermal environmentsIdentify potential bio-signatures for life detection on MarsThe surface of present-day Mars is cold and dry. These conditions are considered inhospitable for life; yet, the geological record contains evidence that liquid water did occur on the surface of earlyMars, suggesting that the planet was warmer, wetter and more hospitable to life. The persistence of water is unclear (Carr 2006); however, it is likely that hydrothermal systems may have developed due to volcanic systems or impact craters and warm/hot water may have been long-lived.On Earth, hydrothermal systems are thought to be a logical candidate for the emergence of life.Phylogenetic evidence suggests that modern hyperthermophiles (microbes that live at high temperature) are closer related to a common ancestor than any other form of life (Woese et al 1990). Therefore, it is inevitable that hydrothermal systems on Mars are potential target sites for life detection missions.The Mars Science Laboratory (MSL) has focused its search for habitable environments in Gale Crater. Impact craters create a wealth of potential habitats for life. As water seeps from the sub surface, a temperature gradient occurs, from high temperatures near the impact rocks to cold surface temperatures. At the surface, an impact lake can be sustained until evaporation occurs.Finding evidence for life is dependent on detecting bio-signatures. For example, microbial activity can effect secondary mineral formation and increase leaching of bio-essential ions. Yet there are a number of questions that are unanswered, such as, what bio-signatures could be used to identify sub surface activity in hydrothermal systems? How would temperature affect these bio-signature? What is their fate on the surface of Mars? The aim of this studentship is to identify potential bio-signatures for life detection in impact craters on Mars.The specific objectives are:To identify potential signatures for biological activity in a hydrothermal system. This will be achieved by culturing microbes isolated from a hydrothermal system and using geochemical analysis.To use geochemical modelling to determine the effect of temperature on bio-signatures. This will be accomplished using the modelling program CHIM-XPT.To determine the possibility of detecting bio-signatures on the surface of Mars using environmental simulation chambers.