Boundary Layers
A distinct boundary layer separates the gray and red
materials. The red material appears to
have been
formed about 50 million years ago and probably was gray when it formed.
After being formed, the material was in the presence
of liquid water and this
caused it to turn red. Later it settled to the bottom of some kind of pool
or ocean of water. Once this water evaporated, the rock and sand dried
together, with the rock encased in the sand. 13 million years ago, the
same volcano became active again and lava flowed in the same region. As
the lava flowed, it immediately "stuck" to some of the older (red) lava and sand
that remained from the earlier action. Also, some of the sand and red
rocks were "captured" within the vesicles of the gray rock as it was forming.
This action preserved the sand within the vesicles.
Everywhere on the meteorite where there is a boundary layer, the two lavas are separated by a very fine butterscotch colored dust. I assume that this is the dust that blew in during the 36 million years that passed between the two lava flows. The red lava, the boundary layer of butterscotch colored sand, and the gray lava are all clearly visible in the picture above. The picture below was taken of the same spot, but under different lighting conditions:
This
transition layer is near several holes that I made in the meteorite. I
wanted to find out how area the red lava covered and how deep it might be.
No where did the red lava seem to be over a centimeter in thickness. In
many places it was much less and the boundary layer between the two layers
was
never more than about 0.5 centimeters. The red layer is apparently more
dense than the gray rock, and thus helped guide the rock as it traveled through
the Earth's atmosphere in a single orientation. The red rock was
apparently on the "bottom" when the rock formed on Mars and was also apparently
on the "bottom" when the rock was heated during its atmospheric traverse, since
the red rock sustained more damage than did the gray.