A specially designed collector gathered dust particles from the comet and stored them on the spacecraft.

VOA: special.2009.09.30

Suppose the planet were hit by a comet-- this happened--something like this happened sixty-five million years ago, so it could happen again.

假设这个星球被一颗彗星击中-,这样的事，大约六千五百万年前,发生过，所以它还可能再发生。

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Many scientists dismiss the comet theory.

VOA: special.2009.01.20

In that event,astronomers were able to observe the icy comet long before it struck the solar system's biggest planet.

VOA: special.2009.08.25

Sometimes,observers see this as a comet's tail, which can be visible to the unaided eye stretching across the night sky.

VOA: special.2011.02.09

Scientists at the Goddard Space Flight Center in Greenbelt,Maryland, found the substance glycine in material brought back to Earth from a comet.

VOA: special.2009.09.30

But the object that struck Jupiter in July is estimated to have been much smaller and harder to see than comet Shoemaker-Levy.

VOA: special.2009.08.25

Since then, scientists around the world have been working to identify substances gathered from Comet Wild-Two.

VOA: special.2009.09.30

But it is the first time an amino acid has been discovered on a comet.

VOA: special.2009.09.30