ES 492: Science in the movies

Lecture 5: Geology of Meteorites

Presented by: Kourtney Crutcher

University of South Alabama

TODAY’S AGENDA Geology of Meteorites

• 1. Meteorites: Comets and Asteroids • 2. Geology of “Small Bodies” • 3. Isotopic Impacts • 4. K-T Extinction: A brief introduction

Figure: www.shewalkssoftly.com

METEORITES: COMETS & ASTEROIDS

Comet Asteroid

A comet is a conglomerate of gasses, dust and ice.

An asteroid is an inactive body of rock material

A meteorite is a portion (meteoroid) of a comet or asteroid that has successfully entered into the Earth’s atmosphere.

The largest “small body” that we have recorded today is the asteroid Ceres. Ceres has a diameter of roughly 1000 km that’s approximately the distance from San Diego, Ca to El Paso, Tx! A small body, is a material with a much lower escape velocity than that of a “large body” such as the Earth. This is the main distinguishing factor (Vereka, 1985).

How small is “small?”

Small Body Defined

Figure: www.usps.com

The minimum amount of speed needed for an object to leave a body’s gravitational pull is known as escape velocity.

Escape Velocity

In Physics...

Figure: http://spiff.rit.edu/classes/phys301/lectures/black_hole/black_hole.html

Small bodies are majorly composed of comets. Some asteroids are thought to be the remnants of some comets that have lost their ice over time. The sun can vaporize the ice associated with comets and cause venting if the nucleus is reached. The manner in which the ice is contained is similar to permafrost. Permafrost is soil that remains at freezing temperatures for at least two years (Vereka, 1985).

Geology of Small Bodies Permafrost

Figure: Buried basal ice from the Laurentide Ice Sheet preserved as massive ice and icy sediments in permafrost, NW Canada. (photo: Julian Murton)

Buried basal ice from the Laurentide Ice Sheet preserved as massive ice and icy sediments in permafrost, NW Canada. (photo: Julian Murton)

Figure: (Vereka, 1985)

Permafrost Outcrop

Just east of Flagstaff, Arizona this crater lies two thirds of a mile in length and approximately 50 feet in depth. The strata has been overturned from the impact that occurred (approximately) 50,000 years ago. Sandstone, limestone, dolomite and mudstone make up the sites stratigraphy (Earth Impact Database, 2016).

Largest Impact Site in the US

Barringer Arizona

Barringer Crater in Arizona, pictured, is the largest impact crater in the United States. It is 0.737 miles (1.186 kilometres) across and is believed to be about 50,000 years old. It is thought to have been formed by a meteorite about 165 feet (50 metres) in diameter. Photograph: Charles/O’Rear/CORBIS

Research suggests that an overlap in the dating of lava flows, meteorite impacts and mass extinctions has made Isotopic data problematic. However, Isotope concentrations are significantly different in meteors than that of the Earth’s crust as seen in the K-T boundary layer (Glikson, 2005).

Isotopic Impacts

An Overview

Figure: (Glikson, 2005)

Figure: http://theodoregray.com/

Geologic Time Scale

Figure: greenforecast.com Artist: Ray Troll

The K-T Extinction More accurately known as the Cretaceous-Paleogene extinction, this event has been widely been accepted to be due to a meteorite impact. This boundary marks the extinction of nearly 75% of the earth’s plants and animals; Most notably, the dinosaurs. Iridium-bearing clay is characteristic of the K-T boundary (only boundary rocks) regardless of location. Because meteorites have a much higher concentration of Iridium than that of Earth, we believe that the mass extinction event is largely due to an asteroid approximately 10 km in diameter (Cowen, 1994).

"Barringer". Earth Impact Database. University of New Brunswick. Retrieved 2016-1-24. Cowen, R. 1994. History of Life. 2nd edition. 460 pp. Blackwell Scientific Publications, Cambridge, Massachusetts. This is

a freshman-level textbook published by Blackwell Science. Copyright Richard Cowen 1994. Available from Blackwell Science, 238 Main Street, Cambridge, Massachusetts 02142, telephone 800-215-1000

Glikson, Andrew. "Asteroid/comet impact clusters, flood basalts and mass extinctions: significance of isotopic age overlaps." Earth and Planetary Science Letters 236, no. 3 (2005): 933-937.

Veverka, Joseph. Planetary Geology in the 1980s. Washington, D.C.: Scientific and Technical Information Branch, National Aeronautics and Space Administration, 1985. Accessed January 24, 2016. http://history.nasa.gov/SP-467/ch7.htm.

References

Deep Impact (1998) MOVIE DISCUSSION Think about the geology of meteorites, their histories and geologic relationship with the earth.

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