Fresh Look at Apollo Moon Rocks Reveals Solar System Secrets

"At some point in the coming year, curators at NASA’s Johnson Space Center in Houston, Texas, will don protective suits and gloves, enter the high-tech laboratory that houses the United States’s trove of Moon rocks, and open a long metal tube that has been sealed since 1972," writes Alexandra Witze, a graduate of EAPS from the Grove group, for Nature. "That’s when Apollo 17 astronauts pounded it into the ground in the Moon’s Taurus-Littrow Valley to collect rocks. It will be the first time in decades that anyone has opened a pristine Apollo sample."

In the meantime, scientists from EAPS and other institutions have been analyzing samples of Moon rock gathered during the Apollo missions between 1969 and 1972, "and using insights from historical and modern Apollo studies to decide the next set of sites to explore on the lunar surface." The timing could not have been better as NASA plans to revisit moon research sometime next year and will be better equipped to gather as much information as possible.

Members of the Grove group recently reported on their work with such samples at the Lunar and Planetary Science Conference (LPSC), which brings together international specialists in petrology, geochemistry, geophysics, geology, and astronomy to present the latest results of research in planetary science. Tim Grove, EAPS Robert R. Shrock Professor of Earth and Planetary Sciences, is a veteran of these conferences, contributing insights and helping to shape future research. He studies chemical differentiation in planets by melting various types of rocks or analogs of them that are prepared in the lab for high temperature and high pressure experiments, with a current focus on lunar mare volcanism. 

Glassy beads in some of the Apollo Moon rocks — which formed during volcanic eruptions — are also yielding discoveries. Megan Guenther, an undergraduate student at the Massachusetts Institute of Technology in Cambridge, has tried to replicate the chemical conditions under which the black glass beads in Apollo 14 rocks probably arose. She found that the beads could have formed at up to 900 kilometres deep, which is much deeper than scientists had suspected.

Guenther, working with Grove, has has been "doing experiments on the most bizarre of the lunar volcanic glass beads that were formed by fire fountain eruptions into lunar vacuum during the time of mare volcanism," says Grove. "They are the Apollo 14 Black Glasses and they contain 16.4 wt. % TiO₂. Most Earth rocks have 1-2 wt. % TiO_2. Also they were erupted super hot, around 1450 degrees ^oC." These samples represent very high temperature and pressure melting, and In the lab, Megan has melted and crystallized samples at pressures up to 4 GPa, equating to depths of about 900 km in the Moon. 

Harry Brodsky, an undergraduate student from Northeastern interning in the Grove lab, followed up on Guenther's work, reporting on a similar moon problem of remelting the deep interior magma ocean cumulates to make mare basalts at LPSC. EAPS graduate student Max Collinet reported on melting of chondrite planetesimals to make the second most abundant chondrite meteorite group in existence -- over 500 unique individual samples of these ureilites have fallen out of the sky.

While these Moon rocks have kept the Grove group busy, they'll soon enough have a fresh sample and new data to build on their work.

The eastern margin of Mare Serenitatis imaged by Apollo 17 in 1972. (Credit: NASA)