Ashima Research - Research
The atmospheres and climate systems of Mars, Titan, and Venus
Terrestrial planets
Mars, Titan, and Venus constitute a family of objects (along with the Earth) that possess “substantial” atmospheres but are still geometrically “thin.” The former term is somewhat arbitrary, but here means continuum (mean free path of particles is orders of magnitude smaller than a scale height) and stable (not rapidly escaping to space or collapsing onto the surface – though Mars plays with this). By “thin”, we mean to exclude the giant plants (Jupiter, Saturn, Uranus, and Neptune) that are mostly or significantly atmosphere. Mars, Venus, and Titan (and Earth) have thin atmospheres overlaying solid or liquid surfaces. These are the objects on which current and past research in this group focuses.
Approach
Science needs hypotheses and observations. In our case, models and spacecraft data.
For planetary atmospheres, the observations tend to be expensive – needing telescopes, or more often, spacecraft. This tends to create a community approach to observations: while instruments remain under the control of “principal investigators” and their science teams, after a “proprietary period” the data from US spacecraft become publicly available via the Planetary Data System (PDS). The PDS archives are a treasure trove, and a significant amount of progress is made across the field by analyses of these data. One major thrust of our research involves the analysis of archived spacecraft data (either via the PDS or through membership of an instrument science team).
Sometimes the archive just doesn’t have what you need. And then you look at the schedule of future spacecraft and find that what you need isn’t even planned. Planetary atmospheres is a somewhat neglected field compared to more hype-driven activities like astrobiology, so this is often the outcome. What to do then? In this case, designing instruments that could be proposed for future flight is the only recourse. A particularly neglected area is in situ dynamical measurement. Another of our major activities is therefore in the design of future instruments and investigations.
Finally, observations mean nothing if you have no expectations with which to compare them. The importance of an observation is only insofar as it can be used to confirm an understanding of a process, or (better yet) show that understanding to be missing something. Atmospheres and climate systems are complex systems. At this stage in the development of the field, the hypotheses are also rather complex – they are contained in the numerical models of the atmospheres that have been developed over the last couple of decades from frameworks originally designed for the Earth. These models are sometimes called climate models, General Circulation Models (GCM), mesoscale models, microscale models, Large Eddy Simulation, etc. Models contain equations that describe our best understanding of processes, and thus the models represent the best predictive theory of the atmospheres (the hypothesis being “the interaction of the processes we include explain the behavior of the atmosphere and climate system.”) They fail often in comparison with new data – those failures highlight areas where neglected processes can no longer be neglected or where process representation is inadequate. In order to complete the scientific process, our final major research area is in model development and use.
Research areas
Given the range of activities, the research page is divided into three main areas. You can get to each of these ares by clicking the links below or in the sidebar to the upper right:
