SSS 2010-04-29
时间：2018-12-02 作者：英语课 分类：Scientific American(四)月
This is Scientific American's 60-Second Science. I'm Karen Hopkin. This’ll just take a minute.
Any school kid can tell you that comets are made of ice. That frozen water burning off is what gives comets their characteristic tails. But asteroids 2 were generally thought to be dry. Or at least frost-free. Now two studies published in the journal Nature suggest that notion may be all wet. Because at least one asteroid 1 appears to be coated by a thin layer of ice. And just that kind of asteroidal 3 frosting could have been the source of our water here on Earth.
The asteroid belt just outside Mars is home to a lot of rocky bodies…including a behemoth with a diameter of 129 miles. This asteroid, called 24 Themis, is one of the largest in the belt and has attracted the attention of astronomers 4 because its nearby traveling companions look like comets.
In the latest studies, scientists used an infrared 5 telescope to spectroscopically examine the asteroid’s surface. And the chemical signature they saw was a good match for water ice, which they found all over the asteroid.
The find provides support for the theory that Earth’s water could have been delivered as ice by an asteroid. Lucky for us we could borrow some from the neighbors.
Thanks for the minute for Scientific American's 60-Second Science. I'm Karen Hopkin.
- Astronomers have yet to witness an asteroid impact with another planet.天文学家还没有目击过小行星撞击其它行星。
- It's very unlikely that an asteroid will crash into Earth but the danger exists.小行星撞地球的可能性很小，但这样的危险还是存在的。
- Asteroids,also known as "minor planets",are numerous in the outer space. 小行星，亦称为“小型行星”，在外太空中不计其数。
- Most stars probably have their quota of planets, meteorids, comets, and asteroids. 多数恒星也许还拥有若干行星、流星、彗星和小行星。
- Astronomers can accurately foretell the date,time,and length of future eclipses. 天文学家能精确地预告未来日食月食的日期、时刻和时长。 来自《简明英汉词典》
- Astronomers used to ask why only Saturn has rings. 天文学家们过去一直感到奇怪，为什么只有土星有光环。 来自《简明英汉词典》