Scientists Target Meteorites at NASA Gun Range

Professor Melissa Strait and Alma undergraduates measure what happens to a meteorite when it is struck by something.

Melissa Strait (back row, center) with Alma students Emma Patmore ’15 and Angie Clayton ’14 (...Melissa Strait (back row, center) with Alma students Emma Patmore ’15 and Angie Clayton ’14 (front row) and researchers at the NASA Ames Vertical Gun Range in California (2013).

When asteroids collide, what happens?

That’s a question of interest for Alma College Chemistry Professor Melissa Strait, who has been involved in NASA-funded planetary research for 15 years.

During her recent sabbatical to the NASA Ames Vertical Gun Range in California, Strait and a team of researchers worked to measure what happens to a meteorite when it is struck by something. The team included Strait, George Flynn from SUNY Plattsburgh, Dan Durda from the Southwest Research Institute and Alma undergraduates.

<em>Alma junior Mason Molesky (right) assists in the vacuum chamber (2015).</em>Alma junior Mason Molesky (right) assists in the vacuum chamber (2015).The set-up isn’t sophisticated: The team suspends meteorites from paperclips and fishing line in a vacuum chamber. Strait cuts aluminum foil into small squares with a rotary blade typically used for quilting — “it pays to be skilled in women’s arts!” she says. The team places the foil squares — “aluminum foil passive detectors” — in four places around the circle of the vacuum chamber. They shoot the meteorite with a gun, and it shatters, puncturing the foil. Cameras record video of the impact, taking up to 250,000 frames per second.

The foils and particles are collected and returned to Alma College for analysis. Students count the tiny holes in the foil — all 10,000 of them — most of which are smaller than the thickness of a pin. A student mounts the aluminum foil and feeds it into a scanner. The resulting scanned images are processed to count the holes and measure their sizes in micro-millimeters in a matter of seconds.

Strait devoted her research sabbatical validating the idea that the pieces don’t shatter outward — they shatter inward in a cone-shape back toward the gun. Strait spent the winter in the Olympic National Park in Washington cutting up the punctured pieces of aluminum foil, scanning them and doing the measurements.

“The scenery out the window helped me keep my sanity,” says Strait.

The team has found that different materials behave differently. For example, pumice, which is so porous that it can float on water, doesn’t shatter; it is just punctured. And it takes more energy to go through thicker foil.

<em>2014 graduate Angie Clayton, in the vacuum chamber.</em>2014 graduate Angie Clayton, in the vacuum chamber.The team started with Earth materials and then began using meteorites. Because it’s hard to find certain kinds of meteorites, they make fake rocks that simulate meteorites. They do this by taking particles of one kind of meteorite, putting them in a “bomb” — basically, a metal container that pressurizes them — and baking them in an oven for several weeks at 150 degrees Celsius (302 degrees Fahrenheit). The result is another type of meteorite.

“It is amusing to see students’ recipes for rocks posted on the wall in the lab,” says Strait.

One of the researchers suspects that when the meteorite is impacted, it’s possible that different compositions travel at different speeds after the impact. The Alma students are working to design an experiment to test this theory. If supported, it could mean that many asteroid samples collected by spacecraft include only certain types of materials, and that the dense centers have yet to be collected and studied.

The team recently secured grant funding from NASA for another three years. The grant provides funding for students to present at conferences, for Strait and her students to travel to California to work with the NASA Ames Vertical Gun Range, and for a paid research position for an Alma student to process the data during the summer.

<em>Emma Patmore secures a meteorite.</em>Emma Patmore secures a meteorite.“Alma College students have an opportunity to participate in research at a fundamental level,” says Strait. “They work on a collaborative project between institutions in a professional lab, and they have the opportunity to present their work at an international meteorite conference. They get the usual benefits of doing research, which is learning to be independent and to create and develop their own ideas.”

Her students joke that the purpose of their research is to help save Earth from an Armageddon-style threat of a large meteor strike — and that blowing it up first is not a good idea. But the applications of her work go beyond that and can help researchers understand how asteroids behave when they strike other asteroids. Others can dream up the applications — and if Strait and her team can figure out the science behind it, they’ll be able to advise those who might need that knowledge for future space missions.


Story published on July 21, 2015