3
votes
1answer
55 views

How would a planetary defence against comets work?

Mappings of practically all potentially dangerous asteroids is well underway. But comets seem almost hopeless to protect against. How far away are approaching comets detected today? How long time ...
6
votes
1answer
94 views

Did a piece of Halley's comet strike the Earth 1,500 years ago?

A friend showed me an article saying that there's evidence that a piece of Halley's comet may have struck the earth about 1,500 years ago. Is anyone here aware of such evidence?
10
votes
1answer
157 views

Why did the Comet Shoemaker-Levy-9 fragments cause such large explosions on Jupiter?

In July 1994, the comet Shoemaker-Levy 9 (D/1993 F2) tidally fragmented and these fragments collided into Jupiter, as per the image below. Image source The question is, what mechanisms resulted in ...