In July, 1994, the fragmented comet Shoemaker-Levy 9 that David helped / discover began its fateful final approach to Jupiter.

 

Instead of being one comet/, it was 20 comets or more, all running down through space, almost like linebackers down a football field. 后卫球员

 

Each comet collided with Jupiter at the speed of above 140,000 miles an hour.

 

Telescopes around the world saw radiant plumes thrown high into space, leaving dark bruises the size of the Earth. Then, in 2009, it happened again.

 

Australian amateur astronomer Anthony Wesley spotted the gigantic impact. 

 

And this black spot, that is about the size of the Pacific Ocean.

 

Once again Jupiter’s dual-gravitational role as solar system traffic cop and cosmic Hoover was on display.

 

Jupiter is the solar system’s vacuum cleaner. Without Jupiter, the Earth will be walloped by a comet, maybe once every 50 years or so. Life would not be possible on the Earth if it were not for Jupiter. We need Jupiter.

 

For thousands of years, Jupiter has been standing guardian to life on Earth. And now we think it possibly might have nurtured some of its own.

 

It used to be thought that the chance of meeting alien life on the planets beyond Mars dropped close to absolute zero, much like the temperature. But that was before we knew where to look.