SEMINAR - Gary Peterson

The Cryogenic World of Triton
Dr. Gary Peterson
Department of Geological Sciences
San Diego State University
Wednesday, October 3rd CSL 422, 1pm

Triton is a large satellite in retrograde orbit around Neptune, the most distant (40AU) of the giant gaseous planets. Surface temperatures average about 40K and are cold enough to condense all of the heavier gases, including nitrogen. A pronounced tilting of Triton's spin axis gives rise to a strongly seasonal climate and the available imagery indicates a deteriorating south polar cap made of nitrogen. Evidently the released nitrogen is being transferred to the north pole and condensing there during the long winter season. Distant though the sun is, it evidently supplies enough energy to provide seasonal transfer of nitrogen much in the same manner that water alternately collects and melts at the earth's poles with the seasons. Triton has been resurfaced and shows little evidence of cratering. Probably the satellite has been heated, evaporating the surface ices and then the released gases have recondensed to provide a new surface. The energy source for the heating would appear to be tidal friction following capture by Neptune. The retrograde orbit of Triton would indicate capture and the lack of surface craters would suggest that the capture was a fairly recent event. Numerous irregular surface textures indicate repeated expansion and contraction and are compared with somewhat similar features on earth. Although the Earth/Triton surface features resemble one another, they would be composed of totally different material.

The Independent Planetologist - Lecture Service

The United States and Russia have long-term Solar System exploration programs. These undertakings have provided us with detailed imaging at a variety of scales of all planets and major satellites except Pluto/Charon. Many more NASA projects are currently underway. Landings on Venus (Russia), Mars (U. S.) and the Moon (Russia and U. S.) greatly enriched the available imagery with rock samples and/or analyses.

How is this voluminous information to be interpreted? The only way to comprehend most of it is to place it within the context of our understanding of the Earth. That field of endeavor is Planetary Geology. The persons most adept at interpreting features of other planets and satellites would be those who are most adept at interpreting similar features on the Earth.

Gary enjoys public speaking and consider it a service to the university and community. Planetary Geology has become a passion and he enjoys sharing that passion. Gary likes meeting people with similar interests and exchanging observations and ideas. Offering public lectures is an excellent way of accomplishing those goals.

Go to the Indepentent Planetologist Web Site for more information....

New Publication - Jared Morrow

Physical and chemical evidence of the 1850 Ma Sudbury impact event in the Baraga Group, Michigan

Peir K. Pufahl*,1, Eric E. Hiatt2, Clifford R. Stanley3, Jared R. Morrow4, Gabriel J. Nelson5 and Cole T. Edwards6

1 Department of Earth and Environmental Science, Acadia University, Wolfville, Nova Scotia B4P 2R6, Canada
2 Department of Geology, University of Wisconsin, Oshkosh, Wisconsin 54901, USA
3 Department of Earth and Environmental Science, Acadia University, Wolfville, Nova Scotia B4P 2R6, Canada
4 Department of Geological Sciences, San Diego State University, San Diego, California 92182-1020, USA
5 Department of Earth and Environmental Science, Acadia University, Wolfville, Nova Scotia B4P 2R6, Canada
6 Department of Geology, University of Wisconsin, Oshkosh, Wisconsin 54901, USA

ABSTRACT

An ejecta layer produced by the Sudbury impact event ca. 1850 Ma occurs within the Baraga Group of northern Michigan and provides an excellent record of impact-related depositional processes. This newly discovered, 2–4-m-thick horizon accumulated in a peritidal environment during a minor sea-level lowstand that punctuated a period of marine transgression. Common ejecta clasts include shock-metamorphosed quartz grains, splash-form melt spherules and tektites, accretionary lapilli, and glassy shards, suggesting sedimentation near the terminus of the continuous ejecta blanket. Sedimentologic and geochemical data indicate that primary fallout from a turbulent ejecta cloud was reworked to varying degrees by an impact-generated tsunami wave train. Observed platinum group element anomalies (Ir, Rh, and Ru) within the Sudbury ejecta horizon are sufficient to suggest that the impactor was a meteorite. Documenting and interpreting the detailed characteristics of the Sudbury ejecta horizon in Michigan have yielded a fingerprint to identify this chronostratigraphic marker in other Paleoproterozoic basins. For the first time a foundation exists to assess the consequences of the Sudbury impact on Precambrian ocean chemistry and early life.

Geology; September 2007; v. 35; no. 9; p. 827-830; DOI: 10.1130/G23751A.1

SEMINAR - Avinoam Rabinovitch

Abstract

We have thoroughly studied the properties of electromagnetic radiation (EMR) emitted from fracturing materials. A model was suggested to explain these phenomena, which helped us relate EMR measured parameters with crack sizes and velocities.

Since EMR appears when fracturing only starts it might be useful as a tool to predict earthquakes in their latent period.

Avinoam's seminar title:
"Properties of electromagnetic radiation from fractures and the possibility of its use for earthquake forecast";
Wednesday the 19th of September 2007


Author of the
Tensile Fracturing in Rocks: Tectonofractographic and Electromagnetic Radiation Methods
Dov Bahat, Avinoam Rabinovitch, Vladimir Frid
Understanding tensile fracture in rocks provides an important key for the interpretation of many problems in structural geology. This book presents a multidisciplinary approach to tensile fracture in rocks (faulting is briefly addressed), starting with an introduction to fracture physics and progressing through tectonofractographic features, characterized both in experimental settings and in geological outcrops. Four examples of sedimentary rocks and two of granites have been chosen to demonstrate the principles and problems in fracture geology. Principles of fracture mechanics and rock mechanics are applied throughout the book, which also explores current understanding about electromagnetic radiation induced by fractures and how such radiation can be used to monitor and predict earthquakes and hazardous collapses in mines. The monograph serves not only as a manual on how to handle specific problems and their solutions in fractual geology but also as a starting point for researchers and graduate students interested in the field of rock fracturing.