托福考试听力部分：练习八

　　Gliese 581 D and E are the planets I wanna focus on now.

　　See, in 2009, a group of researchers made an announcement: these two exoplanets, Gliese 581 D and e do have some earth-like qualities.

　　Gliese 581 D had actually been discovered a couple of years earlier.

　　And when its orbit was originally calculated it was thought to be too far away from its host star to be warm enough to support a liquid ocean, let alone carbon-based life.

　　But then its orbit was recalculated and now we see that Gliese 581 D is within its host’s habitable zone.

　　Student: So it might have an ocean?

　　Professor: Well, conceivably. See, Gliese 581 D weighs 7 times what Earth weighs and it’s unlikely that it’s made entirely of rocks because it’s so massive.

　　The researchers studying it said that it could have a rocky core, an ice layer, a large deep ocean and an atmosphere.