Aug

26

2018

Dr. Candace Kohl

Collection of Meteorites from Antarctic Ice Fields

Location: Geology 3656
Time: 2:30PM

Many very important meteorites have been collected from the “cold storage” of the Antarctic ice sheet. This continent-wide glacier is gradually moving towards the ocean; in some areas erosion by winds exposes meteorites on the surface. Candace will tell us about her experiences as a member of a collection team in Antarctica and also about participation on a team that collected a long core of Greenland ice to analyze for variations in cosmic-ray produced isotopes.

Jul

15

2018

Jean Pierre Williams

Mysterious Cold Spots on the Moon: A New Class of Impact Craters

Location: Geology 3656
Time: 2:30PM

Mapping by the Lunar Reconnaissance Orbiter revealed areas having unusually low temperatures called “cold spots”; regions associated with recently formed impact craters. The cold spots identify the recently formed impact craters. Studying them improves our ability to use impact chronology to date planetary surfaces. The larger cold spot craters are candidate source craters for lunar meteorites; their formation ages are a few hundred thousand to a million years, similar to ejection ages of most lunar meteorites.

Jun

10

2018

Dr. Paul Warren and Prof. John Wasson

Ureilites, diamonds and meteorites from bodies the size of Mercury

Location: Geology 3656
Time: 2:30PM

They will discuss and critique a recent Nature article about diamonds found in a ureilite that fell in the Sudan in 2008. Although the diamonds are relatively small, it is inferred that they originally reached sizes of 100 micrometers; they contain some tiny Fe3(P,S) minerals which have compositions that require pressures only obtained at a depth of >2000 km in a planet the size of Mercury or Mars. These would be the first confirmed evidence of such high static pressures in meteorites. Picture: A colorized scanning transmission electron microscope image showing diamond (blue), inclusions (yellow), and graphite in the Almahata Sitta meteorite. (F. Nabiei, E. Oveisi, C. Hébert/EPFL, Switzerland)

May

20

2018

Dr. Alan Rubin

Searching for links between Asteroids and Meteorites

Location: Geology 3656
Time: 2:30PM

Meteorites are fragmental breccias consistent with the high abundance of impact craters on asteroids and old formation ages of meteorites indicate that they formed on small bodies that cooled within a few million years. Compositional links are provided by spectral reflectivities that match those of asteroids, and densities that indicate the presence of appreciable metal. LL-chondrite samples were returned to Earth from Asteroid 25143 Itokawa; other spacecraft missions will return more samples during the next decade.

Apr

29

2018

Prof. Ed Young

Rocks beyond our solar system - evidence from dead stars

Location: Geology 3656
Time: 2:30PM

White dwarf stars are the stellar cores left behind by Sun-like stars after they have exhausted their nuclear fuel. Some of these dead stars still have rocky bodies orbiting them that are similar to our asteroids. These orbiting objects sometimes fall into the stellar atmosphere and vaporize, releasing their elements which then contribute to the spectral lines visible with telescopes. The chemical similarities between rocks in our solar system and the rock-forming elements floating in the atmospheres of white dwarf stars provide good evidence that rocky planets elsewhere in the Milky Way Galaxy are similar to the rocky planets in our solar system. This, in turn, suggests that Earth-like planets are not unusual.