AW: [meteorite-list] Lunar meteorites-- where do they "hang out"?

From: Norbert Classen <trifid_at_meteoritecentral.com>
Date: Mon Nov 28 18:45:44 2005
Message-ID: <200511282349.jASNnYnE029683_at_ev1.craft.de>

Hi Darren, and Listoids,

You asked:

> Are there any official ideas what happens to lunar meteorites between
> being blasted off the Moon and when they strike Earth? Is it a straight
> shot (so a low transit time) or do they go into lunar orbit and then
> later be captured by Earth, or go directly into Earth orbit, or maybe
> even a seperate solar orbit at the same distance as the Earth/Moon
> system? Or more than one of the above?

Studies on the transition times of various lunar meteorites, obtained by
studies of cosmogenic nuclides within these meteorites, show that both
alternatives occure. However, they also show that the majority of lunaites
are captured by Earth in less than 1Myr after ejection, suggesting that most
lunaites (that land on Earth) do actually hang around inside of the
Earth-Moon system. Good examples are:

- Kalahari 008 and 009 with transition times of less than 1Kyr!
- Dhofar 026 with a rather short transition time of just about 3Kyrs
- Dhofar 081, and pairings with a transition time of about 5Kyrs
- NWA 032/479 with a transition time of about 40Kyrs

Some lunaites took longer to arrive on Earth, such as:

- DaG 400 with a transition time of about 200Kyrs or
- NWA 482 with a transition time of about 300Kyrs

Dunno were these have been hanging out. But I'm pretty sure that the
following (and some other well-travelled fellows) have entered into a
heliocentric orbit, i.e., that they actually left the Earth-Moon system
until they were finally captured by the gravity of the Earth:

- Calcalong Creek with a transition time of 3Myr or
- Dhofar 025 with a sensational transit time of more than 10Myrs.

The latter ones were probably ejected from greater depths within the lunar
surface by high-speed impacts that resulted in higher launch velocities -
enough speed to escape the Earth-Moon system, and to reside in a
heliocentric orbit for a few million years. Go figure!

Lunatically yours,
Norbert
Received on Mon 28 Nov 2005 06:45:28 PM PST