In article ,
Martha H Adams wrote:
Concerning [impact] risks, where is the most safe place on Luna?
Sub-Earth? (Earth directly overhead, remember Luna is orbitally
locked.) The leading side near the equator? The trailing side? More
near the poles? ...

Farside vs nearside vs leading or trailing edge really doesn't make very
much difference. Earth is too small and too far away to provide much
actual shielding, and the Moon's orbital velocity is too slow to be of
great importance.

The safest place is probably hunkered well down in a not-too-big polar
crater. A fair bit of the biggest incoming stuff has orbital velocity
*roughly* in the plane of the ecliptic, so it's coming in roughly at right
angles to the Moon's axis, and it'll be below the horizon in the bottom of
a modest-sized polar crater. (The bigger the crater, the shallower it is.)

Comet debris comes in from all angles... but as it happens, probably the
single biggest impact threat in the Earth-Moon system is comet debris from
a predictable direction: the Leonid meteor showers. When the Leonids
storm, you get roughly a year's worth of meteors in an hour or so... and
they're coming in at 72km/s instead of the usual average of around 20km/s.
(Leonid impacts on the Moon have been seen, as flashes on the night side.)

But the Leonids always come at the same time of year and from the same
direction in the sky, and if memory serves, by chance it's quite close to
the plane of the ecliptic. So in your polar crater, they too are below
the horizon.

However, the bottom of that polar crater may be a trifle chilly...
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |