|Lunar and Planetary Institute|
|Allan H. Treiman
Lunar and Planetary Institute
|Christopher D. K. Herd|
Lunar and Planetary Institute
|John Jones, NASA Johnson Space Center|
David Mittlefehldt, NASA Johnson Space Center
A workshop on Unmixing the SNCs will be held on October 1113, 2002, at the Lunar and Planetary Institute (LPI). The LPI is housed in the Center for Advanced Space Studies, 3600 Bay Area Boulevard, Houston, Texas.
Martian meteorites, despite being all basalts or their derivatives, show an enormous range of chemical and isotopic compositions. In some respects this breadth is greater than that of all basaltic rocks on Earth. Much of the compositional variability can be modeled as mixtures of chemical and isotopic components, and some components have been assigned to specific geological/chemical reservoirs: mantle, crust, atmosphere, regolith, and hydrosphere. If mixing components in the SNCs can be characterized, we will gain insight into hidden aspects of martian geology and geochemistry hitherto unsampled rock types and/or poorly characterized processes and geological environments.
But just what are the components that make up the martian meteorites? What are their chemical and isotopic properties? Do they represent recognizable source rocks, reservoirs, or geochemical processes? Are physical traces of them, mineral grains, or xenoliths recognizable in the meteorites? And how have they come to be mixed?
- Among the shergottites, many seemingly unrelated chemical and isotopic parameters are strongly correlated: e.g., oxygen fugacity, initial Sr and Nd isotope ratios, and La/Yb ratio. These correlations suggest that the martian basalts are mixtures of distinct chemical/isotopic components (rock types or chemical reservoirs), the end members of which may not be represented among the meteorites themselves. Do these components represent mantle sources, crustal contaminants, metasomatic influxes, or what?
- More than 10 years ago, it was shown that some radioisotope parameters in the shergottites could be represented as mixtures from several reservoirs, one of which is consistent with the source material of the nakhlites. Can other radioisotope systems be explained by these same components, are different components required, or are additional components required?
- The heavy noble gases in the martian meteorites are interpretable as mixtures of discrete components, including atmosphere, primitive mantle, and fractionated atmosphere. Are these noble gas components associated with components defined by other chemical and isotopic systems (e.g., an atmospheric signature of high D/H and high D17O)?
- The bulk chemical compositions of some shergottite basalts are represented well as mixtures of lherzolites and other shergottites. Could this relationship imply that these shergottites are impact melts?
- Shock melts in the shergottites can contain the high concentrations of a surface component the martian atmosphere. Are other surface components detectable in the shock melts or elsewhere in the meteorites? For instance, it has been proposed that that shock melts contain traces of regolith or dust. Can this be confirmed or extended? How else might the martian meteorites retain clues to the nature of martian regolith?
If these many proposed mixing components can be characterized, we will gain insight into hidden aspects of martian geology and geochemistry hitherto unsampled rock types and/or poorly characterized processes and geological environments. While important to the petrologist and geochemist, this knowledge could be useful in interpreting spacecraft data about Mars. For instance, if mantle components can be defined, they will help in interpreting geophysical data on the martian interior (as from the MOLA and magnetometer instruments on MGS) by constraining the chemical and thermal states of the mantle. If crustal and regolith components can be recognized, they may be critical in interpreting chemical and mineralogical data for the martian surface, as from the TES instrument on MGS and the Gamma-Ray Spectrometer on Mars Odyssey, or data obtained in situ at the surface by rovers such as MER. In this way, unmixing the martian meteorites can strengthen the ties between sample science and remote sensing science, and further demonstrate the importance of laboratory sample analyses to our deeper understanding of the solar system.
Through this LPI workshop, we seek to assemble experts and researchers in martian geochemistry and petrology to share and diversify their knowledge of martian meteorites and of Mars. Among the questions we will consider are:
- How many chemical/isotopic components can be recognized, and are some meteorites purely a single component?
- What are the chemical and isotopic characteristics that define the different components?
- Do these components correspond to recognizable rock types or processes?
- Do their chemical/isotopic characteristics suggest specific geologic or tectonic settings?
- Are these components predicted by (or consistent with) postulated events in Mars' history, like a magma ocean, a warm wet epoch, or mantle plumes?
The intent of the workshop is to bring new and existing results on chemical and isotopic components of the martian basalts to a single forum through oral and poster presentations. We envision a few invited talks, and many contributed talks with time scheduled for minimally moderated discussion. Poster presentations will have high visibility through short summary presentations and scheduled time for viewing and discussion.
Abstracts are welcome from all disciplines related to the chemical, isotopic, or petrologic characteristics of martian basalts and their precursor components. Studies related to martian meteorites are expected to dominate, but we welcome contributions based on remote sensing data or in situ investigations.
Contingent on review, accepted abstracts will be published in a referenceable abstract volume that will be distributed to workshop participants. Given sufficient interest, the organizers will arrange for a collection of papers derived from the workshop to be published together in a peer-reviewed journal. The workshop abstracts and preliminary program will also be available in electronic format and will be posted on the meeting Web site on or before September 6, 2002. These files will be in PDF format, viewable with version 4.0 or higher of Adobe Acrobat Reader.
The deadline for electronic submission of abstracts will be August 22, 2002.
Abstracts should not exceed two pages (including text, figures, and tables). Abstracts should be submitted using the electronic submission form by 5:00 p.m. August 22, 2002, U.S. Central Daylight Time. Abstracts can be submitted in a variety of formats. Templates and detailed instructions for formatting and submitting your abstract are provided.
Note that electronic submission of files is not always instantaneous; gateways can be shut down temporarily, local routers can fail, network traffic can be heavy, etc. Because your file must be received at the LPI by 5:00 p.m. CDT, it is in your best interest to submit early to allow for possible technical problems or delays in transmission. Please DO NOT wait until the last minute to access the system; access to the Web form will terminate at 5:00 p.m. CDT.
A registration fee of $50.00 ($25.00 for students) is required of each participant to cover catering and related costs. The registration fee does not include meals, travel, lodging, etc. You must register and pay by September 3, 2002, to avoid a late fee of $15.
To preregister, please return the downloadable preregistration form with your payment by September 3, 2002, or you may use the electronic preregistration form if paying by credit card. Non-U.S. participants who state on the preregistration form that they have a currency exchange problem may pay in cash at the meeting and avoid the late fee.
Participants are responsible for making their own travel and hotel reservations. For your convenience, we have provided a list of local hotels and a local area map showing their locations.
For more information regarding the scientific objectives of this workshop, contact one of the organizers listed at the top of this announcement. For information regarding logistics, contact the LPI meeting coordinator, Paula Walley (phone: 281-486-2144; e-mail: firstname.lastname@example.org). For more information regarding abstracts, contact the LPI abstract coordinator, Reneé Dotson (phone: 281-486-2188; e-mail: email@example.com).
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