Heavy Metal
Summer 2016聽| By聽Eric Michael ’96
In the study of physics, some of the best lessons fall from the sky. To help his students better comprehend the composition of asteroids, planets and other celestial bodies, Professor Daniel Britt began building a collection of meteorites in 2003 with the help of Guy Consolmagno, curator of the Vatican鈥檚 meteorite collection.
鈥淢eteorites tell us about the mineralogy of asteroids 鈥� how they鈥檙e put together, how strong they are and how they鈥檒l react to shock,鈥� says Britt, who has worked for NASA on Mars missions, including Pathfinder, the Spirit rover and the Phoenix lander, and was named to Pluto鈥檚 New Horizons mission team.
The current collection of 15 meteorites, which all date from the formation of the solar system 4.6 billion years ago, come primarily from northern Africa and China, and represent a diversity of ancient cosmic materials that are valuable for study.
鈥淲hen you 鈥榮ee鈥� the oldest thing in the solar system, it鈥檚 more concrete, more tactile,鈥� Britt says. 鈥淭here are lots of things we don鈥檛 understand yet, but that鈥檚 what science is about.鈥�
Here鈥檚 what Britt teaches his students about meteorites:
Pallasite
Intense radiation liquefies the internal materials of some asteroids and reorganizes them based on density. This cross section of a pallasite shows what Britt describes as 鈥渁 framework of metal surrounding a bunch of olivine crystals.鈥� As a result of impact, 鈥淲hat you鈥檙e looking at is the boundary between the core and the mantle [of an asteroid].鈥�
Fusion crust
As a meteorite hurtles through space and slams into the Earth鈥檚 atmosphere, friction strips away approximately 90 percent of its mass. 鈥淭he rock literally boils off,鈥� Britt explains, leaving a millimeter-thick 鈥渓ayer of glassy melted stuff.鈥� He says, 鈥淭hat鈥檚 one of the ways you can identify a meteorite 鈥� if it has fusion crust.鈥�
Chondrite
Constructed of many different types of materials drawn together by gravity, these are some of the most common meteorites found on Earth. 鈥淥rdinary chondrites are kind of the sand of the solar system,鈥� Britt says. 鈥淚t鈥檚 basically what all the planets are made of, the stuff that鈥檚 the original material of the solar system.鈥�
Gibeon
Discovered in Namibia in 1836, the Gibeon iron meteorite field is one of the largest on Earth. Iron meteorites are thought to be the remnants of asteroids that had cosmic impacts that stripped off the crust and mantle. 鈥淭he fact that you鈥檝e got a piece of the core in your hand means that the asteroid no longer exists,鈥� Britt explains.
Howardite
Essentially a piece of the melted external crust of an asteroid, howardite is composed of fragments of lighter rocks fused together. According to Britt, this example, found in the Sahara Desert, is likely from the asteroid Vesta, which is one of the largest objects in the asteroid belt between Mars and Jupiter.