[Baps] Torrence Johnson @ MIT; The 26th Wallace Lecture, Thursday 11/08, 4pm 4-370

[Jason Soderblom]

[cid:82dd7603-76d4-4fbe-b92b-77cb184e10a4 at exchange.mit.edu]



[cid:c4884359-672b-4ea6-a39a-25955f0d21d1 at exchange.mit.edu]








Oceans in the Solar System – and Beyond



Thursday, November 8, 2018, 4:00pm, Room 4-370



Dr. Torrence V. Johnson



The origin of the elements through nucleosynthesis inevitably results in the most common solid planet-forming materials available around most stars being iron-bearing silicates and water (in ice form in the outer, colder, regions of the system), with approximately 50/50 proportions.  The last 50 years of exploration of our solar system with telescopes and spacecraft has revealed that a remarkable number of these worlds in the outer solar system, primarily icy satellites, are not merely “frozen ice balls”, but have global-scale water oceans beneath their icy shells, maintained by combinations of radiogenic heating and tidal energy.  Around Jupiter, Europa, Ganymede and Callisto show evidence for global subsurface liquid water oceans, with Europa’s being the most accessible.  At Saturn, tiny Enceladus has a geyser field at its south pole erupting water more or less continuously.  Several of the larger satellites may have subsurface water oceans similar to the Galilean satellites at Jupiter.  In addition to possible subsurface water, Saturn’s largest moon, Titan also has surface lakes and seas of liquid hydrocarbons, primarily methane.

Dr. Johnson will review the history and some of the key findings from the Voyager, Galileo and Cassini missions for the satellites of Jupiter and Saturn and discuss future missions.




[cid:6844b167-0c94-4160-8879-2f655e259aeb at exchange.mit.edu]



Torrence Johnson is one of the world’s leading experts on the natural satellites of the outer solar system.  After earning his undergraduate degree in physics from Washington University in St. Louis, he studied planetary science at Caltech, receiving his Ph.D. in 1970.  His dissertation dealt with telescopic observations of Jupiter’s Galilean satellites.  Since then he has worked in many areas of modern planetary research, including ground based telescopic observations, laboratory and theoretical studies, and planetary spacecraft missions.  Following postdoctoral work at MIT, he joined the staff at Caltech’s Jet Propulsion Laboratory in 1973 and has been heavily involved with JPL’s planetary exploration program. On the Voyager mission, he played a major role as a member of the camera team, planning and analyzing observations of satellites at Jupiter, Saturn, Uranus, and Neptune.  In 1977 he was named Project Scientist for the Galileo mission, and directed the activities of the Galileo science teams through the entire course of the mission, which spectacularly achieved its primary goals in the Jupiter system and continued with extended studies of Europa and Io.  He is currently involved in ongoing research into the properties of giant planet satellites as a team member of the Cassini camera team.   He also served as Chief Scientist for the Solar System Exploration Programs Directorate at JPL from 2002 to 2012 and is currently a Senior Research Scientist in the Planetary Science Section.   In the course of his career he has received numerous awards, including two medals for scientific achievement from NASA and one for outstanding leadership.  He is a member of the American Academy of Arts and Sciences, and an elected Fellow of the American Association for the Advancement of Science, the Explorers Club and the American Geophysical Union.  In 1997 he received an honorary degree in astronomy from the University of Padua, where Galileo made his original observations of the satellites of Jupiter in 1610.







Organizer: Nicholas Makris ( makris at mit.edu<mailto:makris at mit.edu> )



Coordinator: Geoff Fox ( x3‐9344, gfox at mit.edu<mailto:gfox at mit.edu> )

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