[meteorite-list] lunar meteorites

From: AL Mitterling <almitt_at_meteoritecentral.com>
Date: Mon Mar 21 13:24:56 2005
Message-ID: <42347F32.3000809_at_kconline.com>

List,

I Put together a program telling why certain specimens are from the Moon
  and some from Mars and how we know. Thought it might be of interest to
the list. Any comment or mistakes would be good to hear about so I can
correct them. All my best!

--AL Mitterling


Why We Know Certain Meteorites Originate From The Moon
              Put together by AL Mitterling

*First and most important is we have been to the Moon and gathered
  samples to compare to the lunar Meteorites we have recovered.

*Most of the lunar surface is feldspathic. Since lunar meteorites are
  random sampling from the Moon, we see more feldspathic type lunar
  meteorites than any other type.

*High concentrations of aluminum were found each time the Apollo
  orbiters were over highland areas, meaning Plagioclase-rich (hence
  aluminum-rich) anorthosite.

*Only four minerals - plagioclase feldspar, pyroxene, olivine, and
  ilmenite account for about 98% of the crystalline material of the
  lunar crust.

*Some of the most common minerals at the surface of the Earth are rare
  or have never been found in lunar samples. These include quartz,
  calcite, magnetite, hematite, micas, amphiboles, and certain sulfide
  minerals. Many terrestrial minerals contain water as part of their
  crystal structure. Micas and amphiboles are common examples. Hydrated
(water containing) minerals have not been found on the Moon.

*Most of the lunar meteorites have 3?6% FeO, thus, these meteorites are
entirely consistent with make-up from typical feldspathic highlands.

*The iron vs manganese abundance is a distinctive property of lunar
  rocks and serves to distinguish them from terrestrial basalts and all
  other achondrite types.

*The concentration of iron or aluminum serves as a useful chemical
  classification system in lunar rocks. Lunar meteorites that are mare
  basalts (like NWA 032) or breccias composed mainly of mare material
(EET 87521/96008) are poor in aluminum and rich in iron. In contrast,
  meteorites from the feldspathic highlands are rich in aluminum and poor
  in iron.


*Lunar meteorites are achondrites. Achondrites plot on three distinct
  Oxygen isotope lines (17 and 18 compared to 16). Lunar specimens plot
  on one, Martian meteorites (SNC's) plot on another and HED's (Vestoids)
  plot on another distinct one.

*Lunar specimens contain very little iron or metal (much less than 1%)
  unlike their asteroid counter parts which have a high abundance of
  metal (exceptions are some other achondrite types). Lunars are not
  attracted by magnets. Some metal can make it's way into lunar material
  by impact but is low percentage.

*Age plays a part in identification of lunar material. Highlands areas
  date between 4.4 to 4.2 b.y. on the average. Some lunar specimens
(plutonic) have been dated as old as 4.6 billion years old. The Mare
  areas show ages between 4.0 b.y. to 3.2 b.y old.

*Rare Earth Elements (15 of them) play important parts in recognizing
  Lunar material. Lunar material tends to spike positively or negatively
  in the europium anomalities.

* Concentrations of the alkali elements (potassium, sodium, rubidium,
   and cesium) are 10 to 100 times lower in lunar rocks than terrestrial
   rocks. Low concentrations of alkali elements and sulfide-loving
  (chalcophile) elements are one of the most characteristic features of
   lunar rocks.

* All lunar samples have very low concentrations of arsenic compared to
   terrestrial rocks and meteorites. Except for rare felsites, all lunar
   rocks also have low concentrations of potassium compared to
   terrestrial rocks.

*Lunar Meteorites(and samples)contain gases (hydrogen, helium,
  nitrogen, neon, argon, krypton, and xenon)derived from the solar wind
  with isotope ratios different than Earth forms of the same gases. They
  contain crystal damage from cosmic rays. They have crystallization
  ages, determined by techniques involving radioisotopes, that are older
  than any known Earth rocks.


Sources: Meteorites and Their Parent Planets by Harry Y. McSween Jr.
          (newest addition)
          http://epsc.wustl.edu/admin/resources/moon_meteorites.html

--AL Mitterilng
Received on Sun 13 Mar 2005 12:58:10 PM PST