Another very recent abstract on the Hematite deposits from the Sixth International Conference on Mars (2003):

http://www.lpi.usra.edu/meetings/sixthmars2003/pdf/3133.pdf

MERIDIANI PLANUM HEMATITE DEPOSIT: POTENTIAL FOR PRESERVATION OF MICROFOSSILS.

Introduction: Christensen et al. [1], using data
from the Mars Global Surveyor Thermal Emission
Spectrometer (TES), have identified gray crystalline
hematite in a 350 km by 750 km region near Meridiani
Planum. The deposit corresponds closely to the lowalbedo
highlands unit “sm”, mapped as a winderoded,
ancient, subaqueous sedimentary deposit [2].
Christensen et al. [3] interpreted the Meridiani Planum
deposit to be “an in-place, rock-stratigraphic sedimentary
unit characterized by smooth, friable layers composed
primarily of basaltic sediments with approximately
10 to 15% crystalline gray hematite.”
The Meridiani Planum hematite deposit has recently
been designated as the prime landing site for
one of the two Mars Exploration Rover (MER) spacecraft.
The MER landings are scheduled for January,
2004.
Christensen et al. [1] discussed five possible
mechanisms for the formation of this deposit: direct
precipitation from standing, oxygenated, Fe-rich water;
precipitation from Fe-rich hydrothermal fluids; lowtemperature
dissolution and precipitation through mobile
groundwater leaching; surface weathering and
coatings; thermal oxidation of magnetite-rich lavas.
Four of these mechanisms involve the interactions of
rock with water, and thus have implications in the
search for evidence of microbial life.

This abstract is interesting as well:

http://www.public.asu.edu/~bdegreg/LPSCabstract.pdf

DETERMINING THE BIOGENICITY OF MICROFOSSILS IN THE APEX CHERT, WESTERN AUSTRALIA, USING TRANSMISSION ELECTRON MICROSCOPY. B. T. De Gregorio1 and T. G. Sharp1,
1Arizona State University, P.O. Box 871404, Tempe, AZ, 85287-1404,

BD