nai

Project Progress

During the previous year the group led by Brian Toon and Margaret Tolbert at the University of Colorado has made progress in a number of areas. Through a combination of laboratory studies {“The condensation of carbon dioxide on water ice: Implications for the Martian atmosphere” (D. Glandorf, A. Colaprete, M. A. Tolbert, O. B. Toon), Icarus 2002).) and numerical modeling (“Carbon dioxide in an early dense Martian atmosphere”, (A Colaprete, and O. B. Toon), JGR in press, (2002)} we were able to show that carbon dioxide clouds are unlikely to have provided a significant greenhouse warming in the early history of Mars. Therefore the greenhouse model to explain the ancient river valleys on Mars is seriously flawed. We were also able to use the lab data and a model to explain observed clouds on current day Mars {“Carbon dioxide snow storms during the polar night on Mars”, (Anthony Colaprete, Owen B. Toon), J Geophys Res., (2002).} Building on this work, we also suggested that the Martian rivers were not formed under a more equitable climate, but rather are the results of impacts early in Mars’ history. This finding means that there may never have been an extended period with warm temperatures and flowing water on Mars. Instead there may have been high temperature bursts followed by decades or centuries of rainfall interspersed with millions of years of cold temperatures such as those currently found on Mars. This is a far different environment than envisioned previously for early Mars and one that is not conducive to the origin of life at the surface.

We also made substantial progress in understanding the early atmosphere of Earth and the current atmosphere of Titan. Laboratory studies helped us understand how new particles form in Titan’s atmosphere. {“Nucleation Properties of Aerosols in the Atmospheres of Mars and Titan,” (D. L. Glandorf, D. B. Curtis, T. Colaprete, O. B. Toon and M. A. Tolbert), Nucleation and Atmospheric Aerosols 2000, ed. B. N. Hale and M. Kulmala, AIP vol 534, 661-664 (2000) and “Laboratory Studies of Butane Nucleation on Titan Haze Analogue, Hexane, and Acetonitrile: Application to Titan’s Clouds”, (D. Curtis, D. Glandorf, M. Tolbert, O. B. Toon, Mckay C, and B. Khare) Icarus, submitted.}. Further work in progress has shown us what types of particles may have formed in the early terrestrial atmosphere {Trainer, MG et al., Astrobiology yearly meeting 2003, and 2002 A. G. U. meeting.}. We are presently writing a paper on the detailed chemistry of these particles, which is quite interesting from the point of view of sustaining atmospheres with large amounts of methane in them.

Finally we are working on a model for the hydrodynamic escape of hydrogen from early Earth. We have for the first time solved the time dependent escape equations. These should allow us to help solve the problem of the methane abundance in the early atmosphere. This work is collaborative with J. Kasting at Penn State.