Post by Anne Gaudin, University Nantes, CNRS, Laboratoire LPGN, France
On Earth, weathering profiles that have developed in ultramafic rocks under tropical climate show a mineralogical transition between a Fe, Mg-rich smectite zone and an Al-rich kaolinite-bearing zone (e.g. Colin et al., 1990; Gaudin et al., 2005; Yongue-Fouateu et al., 2009). This evolution is due to an intense leaching of Mg2+ cations during the weathering process. The Murrin Murrin (MM) site is an example of such a profile located in the Archean Eastern Yilgarn Craton, in Western Australia. The MM profile is developed in serpentinized peridotite massifs over a 40 m thick sequence (Image 1) and shows three zones: serpentinized peridotites at the bottom, immediately overlain by Fe/Mg-bearing smectites and then Al-bearing phyllosilicates (kaolinite) mixed with iron hydroxides.
Image 1: Weathering profile at the Murrin Murrin site which is currently mined for nickel, located in Western Australia (121º53’41’’E, 28º44’51’’S) (Gaudin et al., 2011).
Posted by megafloods2013 on September 16, 2013
Posted by Dr. Hirdy Miyamoto,
(Re-posted from IAG Image of the Month, November 2007)
In November 2005, the Hayabusa spacecraft performed touchdown rehearsals, imaging navigation tests, and two touchdowns on Itokawa, which is by far the smallest asteroid ever studied at high resolution.
Image courtesy ISAS/JAXA and University of Tokyo
Posted by megafloods2013 on August 8, 2013
Posted by Hirdy Miyamoto, University of Tokyo, Japan.
(Re-posted from IAG Image of the Month, August, 2007)
This image of asteroid 25143 Itokawa, photographed by the Japanese Hayabusa spacecraft during a two-month encounter, September-December, 2005, is suggestive of the “rubble-pile” conception of asteroid formation and structure.
Asteroid 25143 Itokawa. Image courtesy ISAS/JAXA Japanese space agency.
Posted by megafloods2013 on July 19, 2013