[meteorite-list] Lunar meteorite samples help explain early bonnbardment in the inner solar system

From: Shawn Alan <photophlow_at_meteoritecentral.com>
Date: Thu, 2 Aug 2012 12:04:44 -0700 (PDT)
Message-ID: <1343934284.95066.YahooMailNeo_at_web162606.mail.bf1.yahoo.com>

Hello Listers and Lunar Junkies :)

I came across this article about Lunar meteorites and I have to say its a good read on explaining the conditions the inner solar system might have gone through with the help of Lunar meteorite samples. Now all we need is to have a first Lunar meteorite fall and it has be happen around NYC :) preferably Brooklyn while I am walking home from the subway :)

Shawn Alan
IMCA 1633
eBay Store
http://www.ebay.com/sch/ph0t0phl0w/m.html?
http://www.meteoritefalls.com/
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?AN EXTENDED EPISODE OF EARLY BOMBARDMENT IN THE INNER SOLAR SYSTEM:
EVIDENCE FROM LUNAR SAMPLES AND METEORITES.
M. D. Norman1,2 and A. A. Nemchin3,1
Research School of Earth Sciences, Australian National University, Canberra ACT 0200 Australia(marc.norman at anu.edu.au),
3Department of Applied Geology, Curtin University of Technology, Perth WA 6845Australia (a.nemchin at curtin.edu.au).
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?Introduction:
A spike in the flux of asteroid-sizebodies traversing the inner Solar System and impacting
the terrestrial planets at 3.9 Ga has become a keystone
of recent models describing planetary dynamics [1],
the chronology of planetary surfaces [2] and assessments
of the potential habitability of early terrestrial
environments [3,4]. Lunar samples provided the initial
observational data that motivated this idea [5, 6], and
the lunar cratering record now serves as a reference
frame for the cratering chronology of Mars and inner
solar system [7].
The absence of lunar impact melt breccias with ages
between ~4.4 and 3.9 Ga has long been cited as evidence
favoring a relatively low average impact flux
during the interval between planetary accretion and the
formation of many if not all of the lunar basins during
a relatively brief episoce of late heavy bombardment
from ~3.8 to 4.0 Ga [3]. However, large impact events
on the Moon with ages ranging from 4.1-4.3 Ga have
been inferred from recent dating of lunar zircons [8, 9]
from previously unrecognized varieties of lunar impact
melt breccias [10, 11], from clasts in fragmental lunar
breccias [12] and from metamorphic lunar breccias
(granulites) [13]. Here we summarize the lunar sample
evidence for pre-cataclysm (i.e. older than 3.9 Ga)
impact events on the Moon, and suggest that the basinforming
epoch likely spanned a significantly longer
period of time than implied by the Cataclysm Hypothesis.
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http://www.lpi.usra.edu/meetings/earlymars2012/pdf/7051.pdf
Received on Thu 02 Aug 2012 03:04:44 PM PDT