Jeff Nettles, Ph.D.Candidate

Ph. D. Research Area

TITLE : Petrology of Chondrule Precursors and Accretion of Particles in Ordinary Chondrites

My PhD research deals with two processes that were at work in the nebula that formed our solar system: the formation of chondrules, and aerodynamic sorting of nebular particles, such as metal grains. My studies of both these processes should give us some new clues about the way in which the solar system formed.

Chondrules are small, generally-round "balls" that are the dominant constituent of chondrite meteorites. While the formation of chondrules is still largely unknown, we do know that heating of the material in the nebula was involved. Something else we know is that chondrules were not quite the first materials to have formed in our solar system. We know this because chondrules can be found to contain "relict grains" - little bits of crystals whose composition and/or texture don't fit with the other crystals in the chondrule that are "left-overs" from the chondrule-forming process. So, if we know that there were materials that existed before chondrules, what were they? That's what I'm trying to answer with my research. It turns out that the materials that became chondrules were heated to varying degrees - some completely melted, some experienced quite a bit of partial melting, and others experienced only slight partial melting. Since the ones that were only slightly melted look most like the chondrule precursors, I'm studying them to develop an inventory of materials that were the precursors to chondrules. That's the first part of my research.

The second part of my research has to do with sorting of nebular particles in the nebula. It's been shown that the distribution of sizes of chondrules in one meteorite differs from the distribution of chondrule sizes in another meteorite, and this is one of the observations that have led to the idea that there was some sort of sorting mechanism in the nebula. Previous work has shown that the sorting is probably occurring aerodynamically rather than by mass, so my goal is to see how much the shape of a nebular particle (primarily metal grains and chondrules) affected its sorting. To do this, I'm employing X-ray tomography (more commonly known as "cat-scans?), though at much higher resolution that the scans that hospitals use. This way we can get highly-detailed, 3D measurements of the meteorites without having to destroy them. And again, this should give us some exciting new details about the way our solar system formed.

• Nettles, J.W., G.E. Lofgren, and H.Y. McSween, Jr. (2001) Chondrule Precursors In Lew86134 Inferred From Partially Melted Aggregate Chondrules. In Meteoritics and Planetary Science, in press.
  
  
• Nettles, J.W., G.E. Lofgren, and H.Y. McSween, Jr. (2001) Partially-Melted Aggregate Chondrules In Lew86134: Preliminary Analysis Of Textural And Chemical Trends. In Lunar and Planetary Science XXXII, Abstract #1651, Lunar and Planetary Institute, Houston (CD-ROM).
  
  
• Nettles, J.W. , C.R. Coombs, and C. A. Evans (1999) Use of Space Shuttle Imagery to analyze mudflow patterns at Mount Pinatubo, Phillipines. In Lunar and Planetary Science XXX, Abstract #1520, Lunar and Planetary Institute, Houston (CD-ROM).
  
  
• Nettles, J.W., E.L. Dobson, and S.V. Stearns (2000) Use of Fractals in the Spectral Analysis of Hyperspectral Data. In Proceedings of the Sixth International Conference on Remote Sensing for Marine and Coastal Environments, Charleston, SC, p. I-287.
  
  
• Nettles, J.W., J.L. Kennedy, and C.R. Coombs (2000) The South Carolina Underwater Remote Vehicle: An ROV designed for Marine Research in South Carolina. In Proceedings of the Sixth International Conference on Remote Sensing for Marine and Coastal Environments, Charleston, SC, p. II-179.
  
  
• Nettles, J.W, S.V. Stearns, and S.D. Oakley (1999) Using Noise Removal Algorithms For Improved Spectral Analysis Of ATREM-Corrected AVIRIS Data. In Proceedings of the 13th International Conference and Workshops on Applied Geologic Remote Sensing, Vancouver, BC, p. 438-442.
  
  
• C.R. Coombs; J.L. Meisburger, J.W. Nettles (1998) Another Look at Taurus Littrow: An Interactive GIS Database. New Views of the Moon, LPI, Houston, TX, September 1998.
  
  
• Nusbaum, R.L., J.W. Nettles, and S.V. Stearns, (1997) Imaging Spectroscopy Used For Geologic Mapping Of The Tintic Mining District, Utah, USA. In Proceedings of the 12th International Conference and Workshops on Applied Geologic Remote Sensing, Denver, CO, p. 438-442.

Return to the Top of the Page.

Return to Current Research Page

Return to PGI Homepage