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

培养微生物学和地球化学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现今火星表面寒冷干燥。这些条件被认为不适合生命生存；然而，地质记录中有证据表明，早期火星表面确实存在液态水，这表明火星更温暖、更湿润，更适合生命生存。水的持久性是不清楚的（Carr 2006）；然而，由于火山系统或陨石坑，热液系统可能已经发展起来，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者。系统发育证据表明，现代超嗜热微生物（生活在高温下的微生物）比任何其他形式的生命都更接近于一个共同的祖先（Woese et al 1990）。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）一直致力于寻找盖尔环形山的宜居环境。陨石坑为生命创造了丰富的潜在栖息地。当水从地下渗出时，就会出现温度梯度，从撞击岩石附近的高温到表面的低温。在地表，撞击湖可以持续到蒸发发生。寻找生命的证据依赖于探测生物特征。例如，微生物活动可以影响次生矿物的形成，增加生物必需离子的浸出。然而，还有许多问题没有得到解答，比如，什么样的生物特征可以用来识别热液系统的地下活动？温度如何影响这些生物特征？他们在火星表面的命运如何？这项研究的目的是识别潜在的生物特征，以便在火星上的撞击坑中探测生命。具体目标是：确定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。利用地球化学模型确定温度对生物特征的影响。这将使用建模程序chin - xpt来完成。利用环境模拟室确定探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.