Helium-3 exploration in Lunar surface is always related to the exploration of Titanium base oxide minerals.
[I] Scientists estimate there is about 1 million tons of He- 3 on the moon, enough to power the world for thousands of years. TheHe-3 is mainly imbedded in an ore called ilmenite [FeTiO3] which is trigonal rhomohedral.
It is known all the 7 types of naturally occurring crystals have empty spaces (holes/interstities) where the foreign materials (He-3) [GUEST] get entrapped in the mineral [HOST] by van Der Waal's forces in the form of CLATHERATES.
It is interesting to note that the no helium clatherates are known on the earth because the sizes of the empty spaces (hole/interstities) in minerals/ores are much larger on the earth than of helium size (app.40.0pm). Sosmall sized helium escapes from the large sized holes of the minerals on the earth.
But at moon with 1/6 of gravity of earth, these minerals have small sized holes where the the helium-3 can well fit in and remain embedded in them because now the GUEST and the HOST are held by van Der Waal's forces.
[II] The minerals/ores other than ilmenite are: Anorthite (CaAl2Si2O8), Olivine (Mg2 SiO4),Ferrous oxide(FeO), iron cromite(FeCr2O4 ),Thoria(ThO2).
Note:[a] "Appolo" collected samples of the ores from different sites of the moon (named as: A-11,12,14,15,16,17,L-16,L-20) and found that there were significant variations from sample to sample at each site. Some rocks were almost purely of one mineral.
[b]Analysis of the isotopes of the volatile element (Zn) indicates that the Moon differs significantly from Earth in the abundances of zinc isotopes. Scients ascribe this difference to evaporation processes during formation of the Moon by a giant impact. The refractory elements,probably, did not vaporize significantly during lunar formation, leaving their isotopic compositions unscathed by this significant event in Solar System history.
Thanks Dr Manohar. But there are no evidence for helium-3 entrapment in anorthite,olivine or chromite. Ilmenite alone is having something special affinity for trapping helium-3. I would like to know about that it. Thanks a lot.
I, humbly, submit as:
The clathrate is formed as the atomic size of GUEST (He-3) and of the holes (empty sites) of the HOST (limonite) are comparable. On the other hand, the holes in anorthite, olivine or chromite are either narrower (He-3 does not enter) or are wider (He-3escapes) ,i.e. ideal value reaches only between He-3 atomic size and limonite hole size.
i am skeptical of this atomic sized hole theory. ilmenite also absorbs neon and Argon which have very different atomic sizes than Helium ....
Reference:
Geochimica et Cosmochimica Acta
Volume 58, Issue 2, January 1994, Pages 1031–1042
Implanted solar helium, neon, and argon in individual lunar ilmenite grains: Surface effects and a temporal variation in the solar wind composition
R.H. Nichols Jr., C.M. Hohenberg, C.T. Olinger∗
McDonnell Center for the Space Sciences and Physics Department, Washington University, One Brookings Drive, St. Louis, MO 63130, USA
URL: http://www.sciencedirect.com/science/article/pii/001670379490524X
Hello Prof. Parthasarthy
Greetings.
Major source of 3He on lunar surface is Solar wind. Solar wind directly implants ions of He and other noble gases emitted from Sun. 3He (and Ne) contents are much higher (almost two orders of magnitude) in ilmenite than in co-existing minerals such as olivine, pyroxene and plagioclase. The reason is diffusion from ilmenite is much slower than these other minerals. In other words, ilmenite is more retentive than other minerals. As you know abundance of He can significantly affected by diffusion. Therefore, while all minerals are expected to have similar inventory of He, it is ilmenite that could retain the most.
I could find following reference for the latest work. Second link is an older review article there you can specific references citing lower diffusion for ilmenite.
https://www.researchgate.net/publication/225664388_Noble_gas_diffusion_mechanism_in_lunar_soil_simulant_grains_Results_from_4He_implantation_and_extraction_experiments
http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources15.pdf
Hope I could answer your question. I should have seen this question before!
with regards
Article Noble gas diffusion mechanism in lunar soil simulant grains:...
- Badges
- Science topic
- Similar topics
- Data Mining
- Classification