2000 Annual Science Report
University of Colorado, Boulder Reporting | JUL 1999 – JUN 2000
Habitability of Planets
The goal of our research is to understand the factors that influence the long- term habitability of planets.
The goal of our research is to understand the factors that influence the long- term habitability of planets. O.B. Toon’s work is partly sponsored through the University of Colorado Astrobiology Program. Margaret Tolbert’s work and part of O. B. Toon’s work is sponsored by the NASA Ames Astrobiology program. In this latter work we are interacting with the climate-modeling group at Ames and Prof. Jim Kasting of Penn State University who is also a member of the NASA Ames Astrobiology Institute. This report summarizes both projects since they are highly interactive.
Our first project is to understand the role of clouds in planetary climates. We are using laboratory facilities in Dr. Tolbert’s group to guide theoretical modeling of clouds on Mars and clouds on Titan. David Glandorf, a graduate student in the Chemistry Department has finished experiments that show how carbon dioxide condenses onto ice surfaces. This work provides the critical information that is needed to model carbon dioxide clouds in early atmospheres of Mars and possibly Earth, as well as in the current atmosphere of Mars. We have submitted a paper on this work to Geophys. Res. Lett. We have used current spacecraft observations of Martian clouds to test our models that incorporate the laboratory work mentioned earlier. Tony Colaprete, a graduate student in the Astrophysical and Planetary Science Department, has simulated the clouds that may have been present in these early atmospheres, as well as in the current Mars atmosphere. We find that we can reproduce the current cloud properties as observed from Mars Observer. We also find that clouds in early atmospheres tended to cool, not warm the planet, but they don’t totally cancel the greenhouse effect of added carbon dioxide gas.
Another cloud related project is aimed at understanding the clouds of Titan. Dan Curtis, a graduate student in the Chemistry Department, is investigating how methane and ethane will condense on the organic hazes that are thought to exist in the atmosphere of Titan. Similar materials may have once been abundant in Earth’s atmosphere. Our goal is to understand if clouds are likely to form in Titan’s atmosphere, or whether supersaturated vapors are more likely. We plan to use these laboratory studies to guide a theoretical model that Erica Barth is developing. To date we find that episodes of ethane cloud formation may occur every few hundred days on titan: a drizzle every few months. We will compare the model with observations of Titan that are currently available and planned for the Cassini mission in a few years.
Our final project is to understand the role that impacts play in planetary environments. We have previously done extensive studies of the environmental effects of impacts on Earth, work which Elinor Newman is continuing. Now we are trying to determine if the rivers on Mars may have been caused by impact events on the surface, rather than by greenhouse warming as most people currently think. Teresa Segura, a graduate student in the Atmospheric and Oceanic Science Department, has been conducting modeling studies of the Martian atmosphere after a large impact. She plans to spend the summer at NASA Ames consulting with Kevin Zahnle, and Bob Haberle on this project.
PROJECT MEMBERS:Owen Toon
RELATED OBJECTIVES:Objective 5.0
Describe the sequences of causes and effects associated with the development of Earth's early biosphere and the global environment.
Define climatological and geological effects upon the limits of habitable zones around the Sun and other stars to help define the frequency of habitable planets in the universe.
Determine the resilience of local and global ecosystems through their response to natural and human-induced disturbances.