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David L. Hogenboom, Lafayette’s Marshall R. Metzgar Professor Emeritus of Physics, will speak on “Europa’s Crust and Ocean: Hot Science on a Cool Moon” at noon Friday, April 6, in Hugel Science Center room 100.

Sponsored by the Physics Club, the talk is free and open to the public. Pizza and soft drinks will be provided at no cost.

Hogenboom will give an illustrated tour of the surface of the Jovian moon Europa, explaining how various features may have formed and showing how experiments that he has conducted with Megan Daly, a junior physics major from Ballston Lake, N.Y., are helping put constraints on the possible composition and temperature of the ocean.

Daly is one of 11 Lafayette students with whom Hogenboom has worked under Lafayette’s distinctive EXCEL Scholars program, in which students collaborate closely with faculty on research projects while earning a stipend. “I’m more proud of my students and what they’ve done than of my own research,” Hogenboom said in a feature article in The Morning Call in November.

“Recent data from the Galileo spacecraft have convinced many planetary scientists that Europa is covered with an outer layer of H2O, comprising a surface crust of ice and an underlying ocean of water containing salts, sulfuric acid, or both,” he says. “The thickness and nature of the ice crust is hotly debated, however.”

For several years, Hogenboom has been engaged in an experimental program of research on basic physical properties of chemical solutions that are believed to be important elements of the satellites of the outer solar system, and possibly of Mars, as well.

“The most important property I have studied is the density of the solutions in both liquid and frozen phases at the high pressures and low temperatures that pertain to the interiors of these satellites,” says Hogenboom. “Measurements of the absolute densities of these substances and the change in density that accompanies melting and freezing establish constraints on models that others develop for the thermal evolution of the body, for certain tectonic processes that have shaped the surfaces of these moons, and for cryovolcanic resurfacing processes.”

The work has been done in collaboration with Dr. Jeffrey S. Kargel of the U. S. Geological Survey, Flagstaff, Ariz., and has been funded by NASA with a succession of grants. Results have been published in “Magnesium Sulfate-Water to 400 MPa Using a Novel Piezometer: Densities, Phase Equilibria, and Planetological Implications,” ICARUS 115, 258-277 (1995), and “The Ammonia-Water System and the Chemical Differentiation of Icy Satellites,” ICARUS 128, 171-180 (1997).

Hogenboom retired from full-time instruction last spring. He continues to teach a course in planetary astronomy in the fall semester and maintains his research in the physics department.

Hogenboom joined the Lafayette faculty in 1965. He holds doctoral and master’s degrees in physics from Penn State and a bachelor’s degree from the College of Wooster. He has been a visiting senior research fellow at the University of Kent in Canterbury, England; a visiting scientist at the Lunar and Planetary Laboratory at the University of Arizona; and a visiting scientist at the United States Geological Survey, Menlo Park, Calif.

He is a recipient of Lafayette’s Thomas Roy and Lura Forrest Jones Faculty Lecture Award in recognition of excellence in teaching and scholarship and was the first recipient, in 1990, of the Daniel L. Golden ’34 Alumni Association Faculty Service Award recognizing distinguished service to Lafayette through the Alumni Association and alumni activities.

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