Vernadsky-Brown Microsymposium 47

Early Climate and Weathering on Mars

March 8-9, 2008

Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058

The geological history of Mars is characterized by three broad stages: 1) an early Noachian record of valley network and lake formation, suggesting extensive fluvial activity and the possibility of a 'warm, wet' early Mars, accompanied by Tharsis volcanism, 2) the Hesperian period, characterized by extensive global volcanic resurfacing, followed by outflow channel formation, and 3) the Amazonian period, during which internal geological activity lessened, the climate was apparently cold and dry, and variations in spin-axis and orbital parameters caused major migration of polar volatiles and formation of glaciers and related deposits at non-polar latitudes.

The advent of high spatial and spectral resolution orbital and surface remote sensing instruments for Mars has enabled us to begin to understand the primary mineralogy of rock units emplaced in early Mars history, and the interaction of these rocks and minerals with the subsurface and surface climate alteration/weathering environment. We are beginning to determine the alteration and weathering products that define these key periods, and the role of water in these interactions. For example, the hypothesis has been put forward that the Noachian is dominated by water-related weathering producing phyllosilicates and the Hesperian by a different aqueous environment in which sulfates dominated. This trend is interpreted to represent a major change in the characteristics of the atmosphere and climate, perhaps related to internal activity (e.g., mantle convection, volcanism, magnetic field evolution, etc.). It is now possible to turn our attention to the geological environments in which these specific mineral types occur, and to assess the geological processes that may have led to specific weathering products.

This year the Microsymposium will focus on early Mars, addressing the geologic and mineralogic evidence for crustal modification processes in the Noachian and Hesperian, with particular emphasis on the hypothesized transition period at the Noachian-Hesperian boundary. Recent results from Mars Reconnaissance Orbiter, Mars Odyssey, Mars Express, and Mars Exploration Rover missions have provided abundant evidence for these processes and the geologic and mineralogic deposits characterizing these periods. In addition, these same data are now providing clues to the role of water and climate in changing these regimes. Combinations of altimetry, images, and physical, chemical and mineralogical properties are now being used to address ancient crustal materials and Hesperian-Noachian-aged climates on Mars. Furthermore, Mars General Circulation Models (GCMs) and mesoscale models are becoming more sophisticated to the extent that they can be used to make predictions that can be tested with geological observations.

Thus, this seems to be an opportune time 1) to discuss new results in the analysis of deposits that might represent the ancient record of climate change and atmospheric-water-rock interactions, as well as 2) to assess the most recent developments in models for general circulation and climate evolution and their predictions for the Noachian/Hesperian. Mutual discussion of these parallel themes in a workshop mode will help inform both communities of the promise and problems in deciphering the early history of Mars.

The workshop will include several keynote papers on specific aspects of these topics, as well as contributed papers and posters. The key dimension is the workshop mode, which favors extended open discussion not commonly occurring at regular meetings, and we will strive to plan sufficient time for open discussion of important issues raised by the data and keynote presentations. 

Among the key questions to be addressed are:

1. How do the new mineralogic data inform us about primary igneous compositions and the alteration and weathering regime of the surface and subsurface of early Mars, and how do these change with time during the Noachian and Hesperian?

2. What are the distinctive Noachian-Hesperian geological features (e.g., craters, valley networks, lakes and ponds, outflow channels, etc.) from which the record of surface and near-surface aqueous environments and climate characteristics can be interpreted on Mars and how do these change with time?

3. How do distinctive mineralogic and geologic environments correlate stratigraphically, and what does this tell us about processes of climate change during the Noachian-Hesperian?

4. What is the nature of the hydrological cycle during the Noachian, and how did it change in the Hesperian?

5. How can current climate and general circulation models account for the mineralogical and geological record of the Noachian-Hesperian?

The Microsymposium will be held at the Lunar and Planetary Institute in Houston, Texas, beginning at 1 pm on Saturday, March 8, and will conclude Sunday, March 9, by 12 noon. If you are interested in participating in the Microsymposium, please respond to this e-mail by filling in the form below. The Microsymposium will emphasize open discussion format but will be anchored by several invited overviews, posters, and some short contributed papers and commentaries.

We ask that responses requesting presentations or posters be made as soon as possible but no later than January 10th, 2008 to James_Head@brown.edu. Those wishing to attend the conference can register at any time, including up to the time of the conference, but advance notice helps us to plan the program, refreshments and seating. Please forward this announcement to any interested students and colleagues. For further updates, consult: http://www.planetary.brown.edu/planetary/international/micro47.html

Sincerely, Alexander Basilevsky, James Head, Jean-Pierre Bibring, Gerhard Neukum, John Mustard, Michael Wyatt, Francois Forget, and Scott Murchie, Co-convenors.

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