From: g_d_pusch_remove_underscores@xnet.com
vegemite@dualboot.net (Christopher M. Jones) writes:
> g_d_pusch_remove_underscores@xnet.com (Gordon D. Pusch) wrote in message
news:...
>> cray74@hotmail.com (Mike Miller) writes:
>>
>>> If an Earth-like planet was struck by a 1000km-diameter planetoid (a
>>> mini-version of the Mars-sized rock that might have hit Earth and
>>> formed the moon), would it:
[...]
>>> 3) What time scale do the effects take place over?
>>
>> For a straight-on impact, on the order of 1.5 minutes --- the time it takes
>> for the planetoid to move through its own diameter at escape velocity.
>>
>> For a glancing impact, on the order of 90 minutes --- the time it takes for
>> the debris to orbit the Earth once.
>
> Close. Any "lithobraking" glancing impact will send the bulk of
> the impactor on a decidedly sub-orbital path, a mere atmospheric
> impact would probably not stop the impactor from simply passing
> through and heading back out to interstellar space. Even on the
> sub-orbital impact the apogee could be quite high, and it may
> take hours for the impactor to come around again. More likely
> is that substantial amounts of material from the impact (both
> from the impactor and the crust) will head out on low sub-orbital
> trajectories which will reimpact the far side of Earth on time
> scales closer to 45 minutes (half an orbit).
As I noted in another post, "on the order of 90 minutes " means
"within a power of ten of 90 minutes," i.e., probably more than
9 minutes, and probably less than 900 minutes (15 hrs). Between
45 minutes and "several hours" is certainly bracketed within that range.
-- Gordon D. Pusch
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