Author Topic: Earth-crossing objects  (Read 334 times)

0 Members and 1 Guest are viewing this topic.

Offline DumbAss Tanker

  • Hero Member
  • *****
  • Posts: 27685
  • Reputation: +1636/-151
Earth-crossing objects
« on: December 15, 2017, 04:34:34 PM »
I used to check the NASA/JPL tables now and then just out of idle curiosity, and kind of got into it back when Apophis first hit the news.  Assuming they would actually post the truth about a pending cataclysmic collision (Giving no odds on that one), there doesn't appear to be any predicted risk of a known kilometer-plus sized object hitting the Earth for the foreseeable future, aside from an uncertainty about what track Apophis will take after its next near approach (It's a miss, but so close Earth's gravity will have an unpredictable effect on its subsequent trajectory, and there is a small window it may go through which would bring it back around for a true hit later.

However however however....

Both Apophis and a couple of other large objects over a kilometer in size DO pass within a Lunar orbit of Earth this Century.  Passing inside the Lunar orbit actually raises two possible collisions with the Moon per close approach.  Imagine the consequences of an object, especially a metallic one, smacking into the Moon at a few Ks per second, and where a lot of the collision ejecta is going to go....

I expect I'll be checked out by the time these things become an immediate issue, so this is more of an academic interest than a real one.  Thoughts? 
Go and tell the Spartans, O traveler passing by
That here, obedient to their law, we lie.

Anything worth shooting once is worth shooting at least twice.

Offline thundley4

  • Hero Member
  • *****
  • Posts: 39032
  • Reputation: +2049/-124
Re: Earth-crossing objects
« Reply #1 on: December 15, 2017, 05:07:04 PM »
Thoughts?

It would be cool to have a moon with rings.  :rofl:

Offline DumbAss Tanker

  • Hero Member
  • *****
  • Posts: 27685
  • Reputation: +1636/-151
Re: Earth-crossing objects
« Reply #2 on: December 16, 2017, 09:54:57 AM »
I think most of it would end up in our atmosphere, since the Earth has a much stronger gravity and the Moon's escape velocity is relatively low.  Some big chunks maybe get through, though since the Moon is rock rather than metal, even pretty sizable pieces of it would likely blow up in the entry (Like Chelyabinsk) rather than impacting the ground directly.  But all in all a really large amount of ejecta really could have some big climate effects on us.
Go and tell the Spartans, O traveler passing by
That here, obedient to their law, we lie.

Anything worth shooting once is worth shooting at least twice.

Offline thundley4

  • Hero Member
  • *****
  • Posts: 39032
  • Reputation: +2049/-124
Re: Earth-crossing objects
« Reply #3 on: December 17, 2017, 07:28:38 PM »
I think most of it would end up in our atmosphere, since the Earth has a much stronger gravity and the Moon's escape velocity is relatively low.  Some big chunks maybe get through, though since the Moon is rock rather than metal, even pretty sizable pieces of it would likely blow up in the entry (Like Chelyabinsk) rather than impacting the ground directly.  But all in all a really large amount of ejecta really could have some big climate effects on us.


If the moon lost sufficient mass and depending upon the angle the moon is struck, it could end up catastrophic for us. Imagine if the change was significant to affect ocean tides.