在线英语听力室_免费在线英语听力学习网站

In 2008 astronomers¹ discovered surprising amounts of water molecules² where planets were forming near young stars. But how, they wondered, could those molecules survive? They should have been destroyed by ultraviolet radiation. In theory, planetary dust could block out UV rays, but the dust was bound up in the creation of those young planets. So what's protecting the water? Now researchers at the University of Michigan believe they have the answer, which they published in the December 18th edition of the journal Science.

The regions where planets are being created are incredibly chemically productive, rapidly generating new compounds. According to the researchers, some water molecules surround the almost-planet dust and act as almost a sacrificial layer. The water molecules absorb the ultraviolet rays—and, though those molecules are destroyed, the embryonic³ planet is shielded. And the region is producing water faster than the protective layer is being destroyed.

The scientists say this action is similar to our ozone⁴ layer, which blankets us with protective shielding from UV radiation. They tested this idea in computer models and found that the results mirrored the observations. Seems that having water when a planet’s finished requires sacrificing some in the process.