SSS 2011-01-10
时间：2019-01-08 作者：英语课 分类：Scientific American(一)月
This is Scientific American's 60-Second Science. I'm Christopher Intagliata. Got a minute?
The Apollo moon missions ended almost 40 years ago. But for lunar scientists, they're gifts that keep on giving. Researchers studying rocks brought back by astronauts have found that the moon's scarce water has a different chemical signature than Earth water. Which leads to the conclusion that the water probably came from comets. The study appears in the journal Nature Geoscience.
The researchers used what's called an ion microscope to compare the amount of normal hydrogen in the moon rocks to the amount of the hydrogen isotope 1 deuterium, which carries an extra neutron 2. They found deuterium at higher levels than it's found in Earth water—but at levels similar to the comets Hale-Bopp, Hyakutake and Halley. Which suggests comets deposited water on the ancient moon, shortly after its formation four-and-a-half billion years ago.
The finding could also explain a mystery of water on Earth—how the oceans got here. Because if comets battered 3 the moon, they probably hit the Earth, too. Ocean water does have more deuterium than water in the Earth's mantle 4. Maybe, the researchers say, that's because the oceans have an extra dose of melted comet ice.
Thanks for the minute. For Scientific American's 60-Second Science, I'm Christopher Intagliata.
- The isotope ratio is directly used for comparing oils or gases.同位素比率直接用于比较各种石油或天然气。
- How to apply a radio isotope?如何运用放射性同位素？
- Neutron is neutral and slightly heavier than the proton.中子是中性的，比质子略重。
- Based on the neutron energy,the value of weighting factor was given.根据中子能量给出了相应的辐射权重因子的数值。
- He drove up in a battered old car.他开着一辆又老又破的旧车。
- The world was brutally battered but it survived.这个世界遭受了惨重的创伤,但它还是生存下来了。