1. Kieffer, H. H., Jakosky, B. M., Snyder, C. W. & Matthews, M. S. (eds) Mars (Univ. Arizona Press, Tucson, 1992).
2. Carr, M. H. Water on Mars (Oxford Univ. Press, New York, 1996).
3. Haberle, R. M. Early Mars climate models. J. Geophys. Res. 103, 28467–28479 (1998).
4. McKay, C. P., Mancinelli, R. L. & Stoker, C. R. in Mars (eds Kieffer, H. H., Jakosky, B. M., Snyder, C. W. & Matthews, M. S.) 1234–1245 (Univ. Arizona Press, Tucson, 1992).
5. Gladman, B. J., Burns, J. A., Duncan, M., Lee, P. & Levison, H. F. The exchange of impact ejecta between terrestrial planets. Science 271, 1387–1392 (1996).