QUESTION:
I'm curious about the white area in the center of the meteorite.

ANSWER from Bruce Jakosky on July 7, 1997:
You must have been looking at the meteorite that is known as ALH84001. It
was collected in Antarctica in 1984, and just identified as being of Martian
origin a few years ago.  It's the oldest of the dozen or so Martian
meteorites, and it's the one that has evidence that some have interpreted as
being due to organisms living within the rock.  The white stuff is a type of
mineral known as carbonate, and it contains CO2.  It's an important mineral
because it was deposited in the rock from liquid water that flowed through
the rock.  And, if the water was at low temperatures, it is possible that it
contained living organisms such as bacteria from Mars.  There is a real
debate, though, as to whether the temperatures in the water were low enough
for life to exist and whether there really was life.  We don't know the
answer yet.