Formation of Carbonates in Martian Meteorite ALH 84001:
Cool Water Near the Surface of Mars
ALH 84001 igneous age (Ieft side of gray box)
and carbonate age (right) fall in the period of
active aqueous processes on Mars.
Secondary carbonates in ancient
orthopyroxenite ALH 84001 record
key information about the
environment of their formation.
Ehlmann et al. (2011)
http://www.psrd.hawaii.edu/Dec11/ALH84001_Carb.html
Clumped Isotope Thermometry
• Isotopologues of CO2 differ in
how much 12C, 13C, 16O, 17O,
and 18O they contain.
• Mass 47 is useful because it
contains both 13C and 18O,
which have a temperturedependent preference for
residing in the same molecule.
• The parameter 47 derives
from the abundance ratios of
masses 47 and 44, compared
to the value expected if the
isotopes are randomly
Experimental data like these and
thermodynamic principles allow us to
distributed among the
correlate 47 with temperature. The mean
isotopologues.
value of ALH 84001 implies 18°C (±4)
http://www.psrd.hawaii.edu/Dec11/ALH84001_Carb.html
Evaporating Fluids, Precipitating Carbonates
Physical Model:
Fractured near-surface of Mars is saturated at some
depth with water.
Evaporation causes carbonates to form.
Little connection with the atmosphere, so
evaporation causes correlated changes in 13C and
 18O.
http://www.psrd.hawaii.edu/Dec11/ALH84001_Carb.html