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的，但知之甚少的问题。自从尤里早期的实验激发了一代人的想象力以来，许多研究都试图开发模型，以描述简单的有机分子如何能够达到在最简单的生物体中观察到的复杂性。目前还没有一个模型可以充分描述简单的原始有机分子（包含元素H，C，O，N和P）和生命所需的复杂分子（氨基酸，RNA等）的遗传途径。然而，最近已经清楚的是，有机分子，甚至生命本身，对“极端”条件的抵抗力比以往想象的要大得多（即极冷，高温甚至高压）。这里描述的研究的目的是确定高压和高温，例如在地壳最上层通常达到的那些，是否可能在将原始有机分子组织成更复杂和可能的益生分子方面做出重要贡献。原始有机物质在地球最早的时期被大量运送到地球，称为冥古宙，从原始地球的吸积（4.5 Gya）延伸到晚期重轰炸（3.85 Gya）结束。在这一时期，这些有机物质可能由于多次撞击引发的冲击事件以及地球内部有机物质可能的埋藏或俯冲而受到变质压力-温度条件的影响。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，可以形成新的复杂或聚合的有机化合物。复杂的有机分子是启动前生物有机合成的先决条件，并可能提供地球生物圈出现所需的材料。这里提出的研究的目的是调查的生存能力，相关系和分解化学的原始有机分子提供给地球在变质的压力和温度，并调查他们与含水硅酸盐材料的反应性。我们提出的实验，以确定的相位关系和分解化学的原始有机材料中发现的行星际尘埃颗粒（IDP）和微陨石直接观察他们的化学行为，而在高压和高温。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，我们将直接向感兴趣的有机起始材料中添加单晶粘土矿物或IDP。高压-温度实验是在布里斯托大学的外部加热金刚石对顶砧单元中使用其兼容的拉曼和FTIR光谱仪进行的。将在钻石光源和高级光源处收集衍射数据。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.