Center for Meteorite Studies

BJohnsonThe ASU Center for Meteorite Studies is pleased to announce that Brandon Johnson, a graduate student at Purdue University, is the recipient of the 2012 Nininger Meteorite Award!

Brandon's paper, “Impact spherules as a record of an ancient heavy bombardment of Earth”, demonstrates a method to estimate the size and velocity of objects impacting Earth that create a spherule layer, based on the layer thickness and the average spherule size within the layer.

Asteroids hitting the Earth typically vaporize a mass of target rock comparable to the projectile's mass. As this vapor expands in a large plume or fireball, it cools and condenses into molten droplets. For asteroids larger than ~10 kilometers in diameter, these spherules are deposited in a global layer. Spherule layers preserved in the geologic record accordingly provide information about an impact even when a source crater cannot be found.

On Earth, impact craters can be quickly obscured or destroyed by surface weathering and tectonic processes. Thus, Earth's impact history is inferred from estimates of the current day impactor flux or the incomplete impact chronology of the moon. However, using geologic observations of spherule layers, and their method to determine the sizes of the projectiles that created the layers, Brandon and co-author Jay Melosh make the first direct estimates of the Earth's bombardment history. These estimates imply that the impactor flux was significantly higher 2.5 to 3.5 billion years ago than it is today. This conclusion is consistent with a steady decline in the post Late Heavy Bombardment impactor flux and can help constrain dynamical models of the solar system.

Brandon’s research was conducted under the advisement of Dr. H. Jay Melosh.

Each submission was reviewed by a panel of experts from a broad array of fields in meteoritical science.

Category: CMS News

Comments are closed.

Sign Up for Center Updates!

Be the first to learn about CMS events and news; sign up for email updates here!


Upcoming Events

September 2016
Sunday Monday Tuesday Wednesday Thursday Friday Saturday
August 28, 2016 August 29, 2016 August 30, 2016 August 31, 2016 September 1, 2016 September 2, 2016 September 3, 2016
September 4, 2016 September 5, 2016 September 6, 2016 September 7, 2016 September 8, 2016 September 9, 2016 September 10, 2016
September 11, 2016 September 12, 2016 September 13, 2016 September 14, 2016 September 15, 2016 September 16, 2016 September 17, 2016
September 18, 2016 September 19, 2016 September 20, 2016 September 21, 2016 September 22, 2016 September 23, 2016

Earth & Space Open House

September 24, 2016
September 25, 2016 September 26, 2016 September 27, 2016 September 28, 2016 September 29, 2016 September 30, 2016 October 1, 2016

Frequently Asked Questions

Click here to find the answers to the most common questions asked of the Center for Meteorite Studies!

Graduate Student Spotlight - Prajkta Mane

Prajkta Mane received her B.Sc. in Geology from the University of Mumbai (St. Xavier’s College) in 2008, followed by her M.Sc. in Applied Geology from the Indian Institute of Technology …

Meteorite of the Month


September's meteorite of the month is Carancas, an (H4-5) ordinary chondrite that fell in Peru, the afternoon of September 15, 2007. To date, over 340g of material have been recovered. …

CMS News

Catch up on all the latest news from the Center for Meteorite Studies!