Expert: Jayendra Upadhye - 6/1/2004

Question
I am hoping you will be able to answer my questions on meteorites. Is it possible for a meteorite to ricochet off landmasses? What would the effects be of this?
If a meteorite ricocheted off the Earth's atmosphere, what effects would there be then? Also, for it to bounce, how fast/big does the meteroid have to be?
Thank you for taking the time to answer these questions.
Yours sincerely,
Holly

Answer
Hi Holly,
1 - Meteors do recochet off landmasses / planet surfaces.
That is the reason why we got a martian rock on the earth which the nasa people displayed as having fossilised material generated by possible bacterial activity!
  The effects would be just an interplanetary transfer of material if the meteor is small.However if it is a larger body, as the one that struck earth in its infancy, we get something more spectacular such as the moon! The moon is thought to have been the result of such an impact.
  Last but not the least have you given a thought to the huge tides and possible supersonic gales that would result due to the gravitational turmoil rersulting from such a flypast/graze?
2 - A meteor ricocheting off the earth's atmosphere if large would cause all the above mentioned gravitational disturbances such as localised high tides that would follow the path of the meteor.(the meteor would have to be a really large one). Normally nothing spectacular would happen except for the meteor loosing some debris thru heating.
3 - Actually most meteors fly around at about 20 km /sec.
Rather than the speed, the angle is of import here.
Sadly i cant tell what that would be! Apart from an inane "glancing"!You would need to consult some nasa web site for that kind of info holly.
Sorry I could not be absolutely specific and give you figures here.
However I would like to add some interesting generalities concerning energy.(it is mostly energy that decides in these matters).Every ricochet actually involves an energy loss on the part of the meteor which appears as heat. each ricochet slows it down as kinetic energy is lost as heat.
If after a number of such ricochets there is still enough energy left in it, it can escape the earth altogether else, with each hop it will re-enter the atmosphere at an increasingly steeper angle till it finally will "take the plunge"!
Jayen