[meteorite-list] mars iron classification

From: Beda Hofmann <beda.hofmann_at_meteoritecentral.com>
Date: Sat Jan 22 08:23:16 2005
Message-ID: <f06020400be17febe95aa_at_[130.92.224.151]>

I agree with Jeff Pringle that the MER microscopic images show what
is basically a Widmannstaetten pattern. There are obviously taenite
lamellae in what must be kamacite. So "Heat shield rock" HSR clearly
is an octahedrite. Based on the images the bandwidth of kamacite
lamellae is approximately 1.5 mm wich yields to the structural
classification Og (coarse octahedrite). Several chemical groups are
possible, but IAB seems the most likely based on abundance
statistics. Possible inclusions of silicates and large (burned out)
troilites, typical for IAB, would also explain some of the
irregularities seen in the surface of HSR.

I wonder what the reddish dark coating is on HSR (visible on color
images constructed from Sol 352 Pancam images). I first thought it
might be fusion crust, bue the microscopic images show a rather
irregular transition from the metal to that crust, and the reddish
color suggest weathering. It might be a weathering crust from an
earlier, more oxidizing climatic period, later on being partially
removed by sandblasting.

Beda
Received on Sat 22 Jan 2005 08:23:15 AM PST