ORIGIN OF LIFE

摘要

Deciphering the origin of life requires some knowledge of the early planetary environment. Unfortunately, we lack definitive evidence of the atmospheric composition, surface temperature, oceanic pH, and other environmental conditions that may have been important for the appearance of the first living systems on Earth. The rock remnants of the early Archean are extremely scarce and most of the record has been lost. The first indications of life from carbon inclusions in rocks and the oldest fossil record are currently under debate but there is a consensus that life started during the first billion years after the Earth formed. Life as we know it is a chemical phenomenon. The chemistry that could have produced self-organizing systems is the central problem in the origin of life. There are several competing theories for how this chemistry may have arisen. In spite of their diversity, proposals for a prebiotic "soup", for the role of submarine hydrothermal vents, or for the extraterrestrial origin of organic compounds have as a common background assumption the idea that abiotic organic compounds were necessary for the emergence of life. It is possible that a combination of these sources - exogenous and endogenous - contributed building blocks for the origin of life on Earth. In this paper we provide a review of the main ideas on the origin of life from the astrobiological perspective and discuss the probability of life on extrasolar planets.