BIOAVAILABILITY OF ORGANICS FOR LIFE IN THE SOLAR SYSTEM

我们对行星宜居性的理解必然局限于我们对地球上生命的了解。可居住性的一个基本组成部分是生长所需的有机化学能。像火星和木卫二这样可能适合居住的行星体拥有大量可以用作能源的无机化合物（例如，铁、矿物质中的硫酸盐和表面附近的高氯酸盐），但在厌氧微生物代谢中生长的有机基质的可用性尚不清楚。该项目将结合实验和分子微生物学、地球化学和能量预测，以评估微生物生命的能力，以碳质陨石中普遍存在的有机物质为燃料。这些陨石已经在行星体上落下了数十亿年，因此有机碳的含量预计不会受到限制。事实上，最近在火星的盖尔陨石坑发现了类似于在碳质球粒陨石中发现的复杂有机物。地球上的大多数生命都使用有机碳作为生长的基质，然而，火星和其他可能适合居住的行星上的陨石中存在的无数有机化合物的程度是未知的。这代表了我们对地球以外可居住性的理解的关键知识差距，也是这个令人兴奋的多学科天体生物学博士项目的重点。

Our understanding of planetary habitability is necessarily limited to our knowledge of life on Earth. A fundamental and as yet underexplored component of habitability is the availability of organic chemical energy for growth. Potentially habitable planetary bodies like Mars and Europa host a plethora of inorganic compounds that could be used as sources of energy (for instance ferric iron, sulfate in minerals and perchlorate at and near the surface), but the availability of organic substrates for growth in anaerobic microbial metabolism is not well understood. This project will combine experimental and molecular microbiology, geochemistry and energetic predictions to assess the ability for microbial life to be fuelled by organic material prevalent in carbonaceous meteorites. These meteorites have rained down on planetary bodies for billions of years, hence organic carbon is not expected to be limiting. Indeed, complex organic matter akin to that found in carbonaceous chondrites was recently detected at Gale Crater on Mars. Most life on Earth uses organic carbon as a substrate for growth, yet the extent to which the myriad organic compounds in meteorites expected to be present on Mars and other potentially habitable planetary bodies is unknown. This represents a critical knowledge gap to our understanding of habitability beyond Earth, and is the focus of this exciting multidisciplinary Astrobiology PhD project.