Dipartimento di Fisica dell'Università di Genova and IMEM-CNR, Unità operativa di Genova, Via Dodecaneso 33, 16146 Genova, Italy.
Philos Trans A Math Phys Eng Sci. 2013 Jun 3;371(1994):20110585. doi: 10.1098/rsta.2011.0585. Print 2013 Jul 13.
Earth's water is conventionally believed to be delivered by comets or wet asteroids after the Earth formed. However, their elemental and isotopic properties are inconsistent with those of the Earth. It was thus proposed that water was introduced by adsorption onto grains in the accretion disc prior to planetary growth, with bonding energies so high as to be stable under high-temperature conditions. Here, we show both by laboratory experiments and numerical simulations that water adsorbs dissociatively on the olivine {100} surface at the temperature (approx. 500-1500 K) and water pressure (approx. 10⁻⁸ bar) expected for the accretion disc, leaving an OH adlayer that is stable at least up to 900 K. This may result in the formation of many Earth oceans, provided that a viable mechanism to produce water from hydroxyl exists. This adsorption process must occur in all disc environments around young stars. The inevitable conclusion is that water should be prevalent on terrestrial planets in the habitable zone around other stars.
传统观点认为，地球的水是在地球形成后由彗星或湿小行星带来的。然而，它们的元素和同位素性质与地球的不一致。因此，有人提出，水是在行星生长之前通过在吸积盘中的颗粒上吸附而引入的，其结合能如此之高，以至于在高温条件下也能稳定存在。在这里，我们通过实验室实验和数值模拟表明，水在橄榄石{100}表面上在吸积盘中预期的温度（约 500-1500 K）和水压力（约 10⁻⁸ 巴）下离解吸附，留下一个 OH 吸附层，在至少 900 K 的温度下稳定。如果存在一种可行的从羟基产生水的机制，这可能导致许多地球海洋的形成。这种吸附过程必须在所有年轻恒星周围的盘环境中发生。不可避免的结论是，在其他恒星的宜居带中的类地行星上应该普遍存在水。
