Sep

28

2014

Paul Warren

Major Messages of Moon Meteorites

Location: Slichter 3853
Time: 2:30PM

This lecture will briefly cover how we recognize lunar meteorites, what they add to our knowledge of the Moon, and why for many purposes the Apollo lunar samples are still supremely important. This lecture will briefly cover how we recognize lunar meteorites, what they add to our knowledge of the Moon, and why for many purposes the Apollo lunar samples are still supremely important.

Aug

24

2014

Frank Kyte

The most meteorite-rich place on Earth...

Location: Slichter 3853
Time: 2:30PM

Where is it? Unfortunately in one of the most poorly explored places on earth, and on the bottom of the ocean too. But 2.5 million years ago an asteroid deposited more than one kilogram per square meter of meteorite over thousands of square kilometers of the ocean floor near Antarctica.

Jul

20

2014

Kevin McKeegan

Meteorites too small to see: collecting micrometeorites and comet dust

Location: Slichter 3853
Time: 2:30PM

Almost all of the meteorites on display in museums are pebble-sized or larger rocks that come from asteroids. However, most of the extraterrestrial matter coming to the Earth every day is in the form of microscopic cosmic dust, which includes both samples of asteroids and of comets. For decades, NASA has collected this dust high in the Earth's atmosphere using re-purposed U2 spy planes and in 2004 has also collected bonafide comet dust by flying the Stardust spacecraft through the tail of Jupiter-family comet P/Wild2 and returning the sample to the Earth for detailed study. I will discuss these collections, what the cosmic dust looks like, and how its properties compare to those of meteorites.

Jun

29

2014

Alan Rubin

Hot Meteorites

Location: Slichter 3853
Time: 2:30PM

The vast majority of meteorites have experienced relatively high temperatures, ranging from about 600ºC to 1200ºC. As a consequence, these samples have been metamorphosed or melted. Metamorphism involves textural recrystallization, homogenization of mineral chemistry, loss of volatiles, and the formation and growth of new mineral phases. Melting can be partial or total. Among the most important questions in Cosmochemistry is the nature of the mechanism mainly responsible for heating meteorites. One of the top two contenders is heating via the decay of short-lived radioactive isotopes such as 26-Al (aluminum atoms with 13 protons and 13 neutrons) which has a half-life of 730,000 years. The other leading mechanism is collisional heating caused by hypervelocity impacts of projectiles onto asteroidal surfaces. In this lecture, we will discuss the petrologic effects of heating and evaluate the evidence for the leading mechanisms that produced hot meteorites.