Researchers at Arizona State University's Tempe campus will unveil a rock Saturday that was collected by Apollo 15 astronauts, one of six missions in which crews brought samples of the moon back to Earth.

The golf-ball-size rock will be unveiled at 11 a.m. as part of the university's Earth and Space Exploration Day, featuring space-related exhibits, laboratory tours, lectures and other activities.

The rock on display at ASU is part of a larger piece known as "Great Scott," after astronaut Dave Scott, who collected the sample in 1971.

During the Apollo moon missions of the late 1960s and early 1970s, astronauts brought back 842 pounds of lunar rocks, pebbles and sand. Most of the materials are stored at NASA's Johnson Space Center in Houston. But each year, NASA loans out some samples for research or education to universities and museums.

Mark Robinson, a professor in ASU's School of Earth and Space Exploration, wrote the proposal to NASA for the loan.

Robinson is the principal investigator for the Lunar Reconnaissance Orbiter Camera, which is attached to an unmanned spacecraft that has been circling the moon for more than two years. The camera system has captured the sharpest images ever taken from orbit of some of the Apollo landing sites.

The 3.3 billion-year-old moon rock loaned to ASU will be displayed near the lunar camera's science-operations center in the Interdisciplinary A building, a place where people can see researchers working and can view images of the moon.

Robinson said visitors walk out of the center excited after seeing the images. He said he expects the addition of the moon rock to add to their positive feelings about the moon.

Bullet-proof glass surrounds the moon rock. A spotlight is planned to highlight the rock's gray and black-flecked surface. The display is designed to rotate slowly, allowing people to view the piece from various sides.

"It should be a very unique display," said Samuel Lawrence, a planetary scientist at ASU.

The moon rock is on loan from NASA for five years with an option for renewal.

Reach the reporter at anne.ryman@arizonarepublic.com or 602-444-8072.