Work has begun on evaluating isotopic signatures of life and hydrological processes on Mars, with specific focus on Ca and Fe isotopes.For Ca isotopes there is a need to better constrain the equilibrium isotopic partitioning associated with inorganic processes to better assess evidence for organic fractionation.Two experiments are in progress.In one, calcite will be grown and equilibrated with dissolved carbonate in the laboratory at temperatures between about 10°C and 70°C (C and O isotopes will be measured as well to assess kinetic effects).The materials for this experiment are being assembled and the experiment design worked out. The second approach will be to use a natural terrestrial system where dissolved carbonate and solid calcite are expected to be in equilibrium. The system chosen is pore water in a deep-sea sediment made up mostly of carbonate ooze.Samples have been obtained and analyses are in progress.A substantial effort is also underway to improve the precision of measurement of d⁴⁴Ca using a new multi-collector TIMS instrument. We are collaborating with Will Dietrich and Michael Manga (below) to evaluate the origin of Martian channels by studying box canyons on the Snake River Plain. Samples have been collected and sample preparation has begun to establish the age of one canyon using cosmogenic He.In the coming year, the work already started will be continued, and in addition we will be working on Ca and Fe isotopes in volcanic hot and cold springs to characterize these environments, and making measurements on Martian meteorites.