Metamorphism of primitive organic molecules in the early Earth and implications for the origins of prebiotic molecules.

地球生物圈的形成是一个基本问题，但人们对这个问题知之甚少。尤里的早期实验激发了一代人的想象力，自那以后，许多研究人员都试图建立模型，来描述简单的有机分子是如何达到在最简单的生物体中观察到的复杂性的。目前还没有一个模型能够充分描述从简单的原始有机分子（含有H、C、O、N和P元素的分子）到生命所需的复杂分子（氨基酸、RNA等）的遗传途径。然而，最近越来越清楚的是，有机分子，实际上是生命本身，对“极端”条件（即极冷、高温甚至高压）的抵抗力比以往想象的要强得多。这里描述的研究的目的是确定高压和高温，比如在地壳最上层通常达到的高压和高温，是否可能在将原始有机分子组织成更复杂的、可能是益生元分子的过程中起到重要作用。在地球最早的冥古宙时期，即从原地球增生期（4.5千古年）到晚期重轰击期（3.85千古年），大量的原始有机物质被运送到地球。在这个时代，这些有机物质可能受到变质压力-温度条件的影响，这是由于反复的撞击引起的冲击事件以及地球内部有机物质可能被掩埋或俯冲的结果。我们最近对简单有机酸的实验表明，在变质压力和温度（0.5-10 GPa和300-1000 K）下，可以形成新的复合物或聚合有机化合物。复杂的有机分子是开始生命前有机合成的先决条件，并可能为地球生物圈的出现提供所需的物质。本研究的目的是研究在变质压力和温度下传递到地球的原始有机分子的生存能力、相关系和分解化学，并研究它们与含水硅酸盐材料的反应性。我们提出了通过直接观察行星际尘埃颗粒和微陨石在高压和高温下的化学行为来确定其相关系和分解化学的实验。必要时将使用同步加速器x射线衍射获得结构信息。在实验的第二阶段，我们将在感兴趣的有机起始材料中直接添加单晶粘土矿物或IDP。高压高温实验是在布里斯托尔大学外部加热的金刚石砧细胞中进行的，使用的是兼容的拉曼光谱仪和傅里叶红外光谱仪。衍射数据将在钻石光源和高级光源处收集。这些实验的结果将使我们能够准确地评估原始有机分子对地球生物圈和大气起源的贡献。

The formation of the Earth's biosphere is a fundamental yet very poorly understood problem. Since the early experiments of Urey, which captured the imagination of a generation, many researches have tried to develop models that can describe how simple organic molecules could have attained the complexity observed in even the simplest form of living organisms. Currently there is no model that can adequately describe a genetic pathway from simple primitive organic molecules (those containing elements H, C, O, N, and P) and the complex molecules (amino acids, RNA, etc) required for life. However, what has become clear recently is that organic molecules, and indeed life itself, are much more resistant to 'extreme' conditions than ever imagined (i.e. extreme cold, high temperatures and even high pressures). The purpose of the research described here is to determine whether high pressures and temperatures, such as those commonly achieved in the uppermost strata of the Earth's crust, can possibly have contributed in an important way in organizing primitive organic molecules into more complex and possibly prebiotic molecules. Primitive organic materials were delivered to Earth in mass quantities during the earliest time period of Earth called the Hadean Era, which extended from the accretion of proto-Earth (4.5 Gya) to the end of the Late Heavy Bombardment (3.85 Gya). During this era, these organic materials may have been subjected to metamorphic pressure-temperature conditions as a consequence of repeated impact-induced shock events as well as possible burial or subduction of organic material in Earth's interior. Our recent experiments on simple organic acids have shown that at metamorphic pressures and temperatures (0.5-10 GPa and 300-1000 K) new complex or polymerized organic compounds can form. Complex organic molecules are a prerequisite for the initiation of pre-biotic organic synthesis and possibly provide the material required for the emergence of Earth's biosphere. The objective of the research proposed here is to investigate the survivability, phase relations and decomposition chemistry of primitive organic molecules delivered to Earth at metamorphic pressures and temperatures and to investigate their reactivity with hydrous silicate materials. We propose experiments to determine the phase relations and decomposition chemistry of primitive organic materials found in interplanetary dust particles (IDP) and micrometeorites by directly observing their chemical behavior while at high pressure and temperature. Structural information will be obtained as necessary using synchrotron x-ray diffraction. In the second phase of experiments we will add either single crystal clay minerals or IDP directly to the organic starting material of interest. High-pressure-temperature experiments are made in externally heated diamond anvil cells at the University of Bristol using their compatible Raman and FTIR spectrometers. Diffraction data will be collected at the Diamond Light Source and the Advanced Light Source. The results of these experiments will allow us to accurately assess the contribution of primordial organic molecules to the origin of Earth's biosphere and atmosphere.