NOTE- PLEASE DON'T ANSWER HERE. I'M DELETING HERE AND MOVING TO SPACE EXPLORATION SE. https://space.stackexchange.com/questions/32411/the-dreaded-apocalyptic-asteroid-approaches-earth-but-lands-safely-on-the-moon


An asteroid approaches and the Moon 'catches' it in the same way that a sports player catches a ball - that is to say by matching the velocity of the hand to that of the ball.

Could a lucky slingshot approach cause this to happen?

Assuming that the Moon has no atmosphere, my intuition tells me that there must be a direction and velocity such that an asteroid can do this. Does mathematics say otherwise?

In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the path and speed of a spacecraft


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    $\begingroup$ See it this way: since there are no aerodynamics involved, the whole process is entirely reversible. So you have to imagine an asteroid sitting quietly on the Moon's surface, then suddenly taking off and disappearing into deep space, just like that. Clearly this is not something you can imagine, and therefore the reverse is also not possible. Your best bet is that the asteroid comes in at a very shallow angle to the Moon, scrapes along its surface for a while, and eventually skip-stones to a halt without too much damage to it. $\endgroup$ – MichaelK Nov 29 '18 at 11:56
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    $\begingroup$ I'm voting to close this question as off-topic because the author has already decided to move the question. $\endgroup$ – StephenG Nov 29 '18 at 12:00
  • $\begingroup$ I have voted to close my own question. I'm getting a note saying I can't delete. I'm now stuck with both questions open. This has been reported to the mods by Mołot so hopefully it will get resolved. Apologies to all.– chasly from UK 22 mins ago $\endgroup$ – chasly from UK Nov 29 '18 at 12:06
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    $\begingroup$ I've closed the question here for you @chaslyfromUK $\endgroup$ – Tim B Nov 29 '18 at 12:07
  • $\begingroup$ It needs to be a very slow moving asteroid. and moving in precisely the right vector. That's the hardest part of your question as if getting the velocities right isn't hard enough. $\endgroup$ – a4android Nov 30 '18 at 1:38

There is a gravity interaction between Moon and asteroid. It is the same interaction that prevents things from flying away. Thus, for an object falling on the Moon, minimal possible speed of impact is the same as Moon escape velocity, roughly 2.38 km/s

Gravity assist works, because speed is increased when getting closer to the planet. You can use Mars to slow down something in relation to Earth or sun, but you cannot use it to slow it down in relation to Mars.

  • $\begingroup$ Hi, Apologies. I'm deleting and moving to Space Exploration. Please feel free to answer over there. I understand what you are saying but I'm not convinced - that's why I'm asking. $\endgroup$ – chasly from UK Nov 29 '18 at 11:31
  • $\begingroup$ @chaslyfromUK don't say you are deleting. Delete, or do not delete. As for space exploration, I'm pretty sure something similar was already asked, so be sure to search before you ask. $\endgroup$ – Mołot Nov 29 '18 at 11:33
  • $\begingroup$ @chaslyfromUK Also, astronomy stack seems to say the same about impact / escape velocity. See astronomy.stackexchange.com/a/20806 $\endgroup$ – Mołot Nov 29 '18 at 11:34
  • $\begingroup$ I'm getting a note saying I can't delete. I'm now stuck with both questions open. $\endgroup$ – chasly from UK Nov 29 '18 at 11:42
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    $\begingroup$ I have flagged for diamond moderator attention, they can do more than we. $\endgroup$ – Mołot Nov 29 '18 at 11:43

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