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Microsymposium 49 poster

March 21-22, 2009
The Woodlands Waterway Marriott Hotel and Convention Center,
Waterway Ballroom 8
1601 Lake Robbins Drive, The Woodlands (Houston), Texas 77380 USA

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Planetary volcanic records provide evidence for the nature and state of the mantle in space and time, crustal formation and evolution processes, and a basis for establishing the geodynamical and thermal evolution of planetary bodies. 

During the more than 30 years since the flybys of Mariner 10, the question of the nature and extent of volcanism on Mercury has been controversial because of the similarity of many plains units on Mercury to bright plains on the Moon (the Cayley Formation), shown by Apollo 16 to be of impact origin.  New data from the first two MESSENGER flybys has shown that Mercury is indeed characterized by extensive plains of volcanic origin, found in a variety of different environments, and including extrusive landforms (shields, vents) and related deposits of apparent pyroclastic origin. These plains are associated with extensive, globally distributed tectonic structures of contractional origin, raising the question of the relationships between the ascent and eruption of magma and the state of stress in the lithosphere.  New MESSENGER data are providing an emerging picture of the nature of volcanism on Mercury, its diversity and global extent, and its relationships to the thermal and tectonic history of the planet.  Important new questions are being posed, designed to be addressed by the orbital phase of MESSENGER operations and the BepiColombo mission.

In the more than 30 years since Luna 24, the last lunar sample return mission, the role of volcanism on the Earth's Moon has become much more well documented. A diversity of volcanic styles has been observed (from Io-like pyroclastic plume deposits to steep-sided domes involving very viscous magma), and the chronology and mineralogy of mare basalt emplacement has been studied in all of the major impact basins.  Lunar samples have provided a chronology for initial primary crustal formation (the anorthositic crust) and subsequent secondary crustal evolution (the emplacement of mare basalts).  These data have given rise to a range of models for possible early mantle overturn, mantle partial melting, the ascent and eruption of magma, and the relationships to early thermal structure and regional thermal perturbations, such as impact basin formation.  From these findings, fundamental new questions have been posed that will be addressed by the international armada of spacecraft exploring the Moon in this decade and beyond.  

We have begun a new era of exploration of Mercury and the Moon. The synergism that will come from comparisons of the record of volcanism on the two planetary bodies will be essential to the success of understanding each individually.  Important questions for both the Moon and Mercury that will be considered during the Microsymposium include:

1.  Eruption StylesWhat is the range of eruption styles/associations on the Moon and Mercury, how do they compare, and what does this mean for mantle and crustal petrogenesis?  New data from both the Moon and Mercury question current volatile-depletion paradigms.  What is the source of magmatic volatiles and how do they relate to planetary evolution models?

2.  Chronology and FluxWhat is the range of ages of volcanic deposits on the Moon and Mercury?  How can impact crater chronologies on Mercury and the Moon be compared?  How does volcanic flux change with time? How closely are volcanic deposits correlated with the Late Heavy Bombardment?

3.  Crustal Composition and Structure: How are volcanic deposits similar to and different from other crustal mineralogies and compositions? What are the implications for their genesis?  Is there evidence for mantle overturn events on both bodies?

4.  Linkage of Volcanism to Impact Processes: What is the relationship of impact basin formation and subsequent volcanic filling?  What is the role of basin ejecta-emplaced plains deposits on both bodies?  Do impact melt deposits play a more consequential role on Mercury than the Moon?  

5.  Linkage of Volcanism to Planetary Evolution Trends: What is the relationship of magma ascent, eruption and flux to planetary thermal evolution and the state of stress in the lithosphere?  What are the predictions of thermal evolution models for Mercury and the Moon and how do they compare with observations?

Sincerely,

Alexander Basilevsky, James Head, Harald Hiesinger, Carle Pieters, Lionel Wilson, Co-convenors.

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Program

Saturday, March 21st.

Eruption Styles and Petrogenetic Implications:  What is the range of eruption styles/associations on the Moon and Mercury, how do they compare, and what does this mean for mantle and crustal petrogenesis?  New data from both the Moon and Mercury question current volatile-depletion paradigms.  What is the source of magmatic volatiles and how do they relate to planetary evolution models?

The Observed Geological Record:
1:00 PM: The Geological Record of Volcanic Eruption Styles on the Moon and Mercury:  Jim Head

The Role of Volatiles:
1:30 PM: Lunar Dark Mantle and Pyroclastic Eruptions: Lisa Gaddis

1:45 PM: Evidence for Pyroclastic Eruptions on Mercury and Implications for Volatiles: Laura Kerber

Physical Volcanology:
2:00 PM: Models for the Ascent and Eruption of Magma on the Moon and Mercury: Lionel Wilson

2:30 PM: Effects of Membrane and Flexural Loading Stresses on Magma Ascent in and Around Large Impact Basins on Mercury and the Moon: Patrick McGovern

3:00 PM: Discussion

Chronology and Flux:  What is the range of ages of volcanic deposits on the Moon and Mercury?  How can impact crater chronologies on Mercury and the Moon be compared?  How does volcanic flux change with time? How closely are volcanic deposits correlated with the Late Heavy Bombardment?

The Observed Geological Record:
3:15 PM:  Synthesis and Chronology of Lunar Mare Basalts from Crater Size-Frequency Data: Harald Hiesinger

3:45 PM:  Global Lunar Surface Mapping and New Age Dates for Mare Volcanism from the Lunar Farside from the Kaguya Terrain Camera: Junichi Haruyama

Crater Chronology:
4:15 PM:  Chronology of Mercury Geological Units from Crater Size Frequency Data:  A View from MESSENGER: Clark Chapman

4:45 PM: Discussion

Linkage of Volcanism to Impact Processes: What is the relationship of impact basin formation and subsequent volcanic filling?  What is the role of basin ejecta-emplaced plains deposits on both bodies?  Do impact melt deposits play a more consequential role on Mercury than the Moon?

General Basin Character:
5:00 PM:  Kaguya Lunar Basin Topography and Gravity Results: Sho Sasaki

5:30 PM:  Impact Basin Ejecta Emplacement and Landscape Resurfacing: New Evidence on the Mercury "Plains Problem" from MESSENGER Data:  Caleb Fassett

Reception and Further Discussion: 6:00 PM

Adjourn for the day:  6:30 PM

Sunday, March 22nd

Crustal Composition and Structure: How are volcanic deposits similar to and different from other crustal mineralogies and compositions? What are the implications for their genesis?  Is there evidence for mantle overturn events on both bodies?

8:30 AM: Composition of Volcanic Rocks on Mercury:  Ann Sprague

9:00 AM: Perspectives on Mercury Crustal Composition from High-Temperature Laboratory Experiments and Mixing Models:  Joern Helbert

9:30 AM: Update on Status of Lunar Spectroscopy and Implications for Mercury Science: Carle Pieters

10:00 AM: Spectroscopy and Crustal Composition on Mercury: Preliminary Results from MESSENGER MASCS Instrument: Greg Holsclaw

10:30 AM: Is There Any Exposed Primary Crust on Mercury or Is It All Volcanic?: Dave Rothery

Linkage of Volcanism to Planetary Evolution Trends: What is the relationship of magma ascent, eruption and flux to planetary thermal evolution and the state of stress in the lithosphere?  What are the predictions of thermal evolution models for Mercury and the Moon and how do they compare with observations?

11:00 AM: Why Can't Mercury Be More Like the Moon:  A Discussion: Sean Solomon

The Present and Future:
11:30 AM: MESSENGER's Third Flyby of Mercury and the Orbital Mission:  The MESSENGER Team

11:45 AM: The BepiColombo Mission to Mercury: Dave Rothery

12:00 PM: Adjourn