May

14

2017

Prof. Kevin McKeegan

The Great American Eclipse of 2017

Location: Geology 3656
Time: 2:30PM

On Monday, August 21, 2017, a total eclipse of the Sun will be visible in the continental United States for the first time in almost 40 years. During a total eclipse the Sun is completely hidden by the Moon, the sky becomes dark, and the faint atmosphere (corona) becomes visible - looking like a beautiful halo. The eclipse will be total along a track stretching from Oregon to South Carolina. In Los Angeles the eclipse will be only partial with 2/3 of the Sun being eclipsed. Kevin will discuss a few historically important eclipses, some general eclipse phenomena, and where and how to view the total eclipse. Photo credit: NASA

May

9

2017

Prof. John Wasson

It Fell From The Sky!

Location: Fowler Auditorium
Time: 6PM

On April 3, 1916, the 139-pound Treysa iron meteorite fell in Germany. Witnesses reported hearing a thunder-like detonation and seeing a cloud of smoke as a result of the fall. Alfred Wegener, a pioneering geophysicist who hypothesized continental drift, used eyewitness reports to calculate where the meteorite came down. After a suspenseful year-long search, the meteorite was extracted about half a mile from the predicted location. Meteorite falls are spectacular and captivating. Fragments that can be found in our backyards connect us all to far-off worlds and the origins of the solar system. Come and hear more about their impact throughout history and today. The event is free and open to the public. Reserve your seat today at meteorites.eventbrite.com!

Apr

23

2017

Dr. Steve Chesley

The Osiris Rex sample-return mission to the asteroid Bennu, a probable source of carbonaceous chondrites

Location: Geology 3656
Time: 2:30PM

The Osiris Rex mission was launched in September 2016. It will rendezvous with Asteroid Bennu in 2018 and spend 1.5 years mapping the surface. It will then sample the surface and return 60-2000 g to the Earth in 2023. It is the first US asteroid sampling mission.

Mar

12

2017

Post-doctoral fellow Roger Fu

The water-rich interior of dwarf planet Ceres

Location: Geology 3656
Time: 2:30PM

By convention, solid solar system bodies are often classified as rocky (e.g., the Earth, the Moon, and Mars) or icy (e.g., Pluto and most satellites of the gas giants). However, new data from the NASA Dawn spacecraft has revealed that the dwarf planet Ceres, the largest object in the asteroid belt at 940 km diameter, does not fall neatly into these categories. He will talk about how the morphology and spectroscopy of the surface point to a composition of less than 30% water ice with the remaining >70% consisting of rock and salts. Even so, intriguing features observed on Ceres suggest localized regions enriched in sub-surface ice and, possibly, the existence of an ancient global ocean during its early history. Picture credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Feb

26

2017

Emeritus Prof. John Wasson

Formation of tektites in thermal plumes: no craters required

Location: Geology 3656
Time: 2:30PM

Tektites are glassy samples with interesting shapes (e.g., teardrops) and compositions similar to soils and shales that formed as a result of weathering the continental crust. Since 1960 the consensus view has been that tektites are crater ejecta. However, high concentrations of 10Be (half-life of 1.5 My) show that tektites are made from soils from the upper 50 centimeters of the crust. The best model seems to be thermal plumes resulting from accreting asteroids or comets that disintegrated and deposited their entire energy in the atmosphere, similar to the 1908 Tunguska event. Figure: Thermal plume after Glasstone and Nolan