Science has come a long way since NASA launched the Apollo 17 mission. Over the last 50 years, researchers have developed advanced technologies and techniques that far surpass those available in 1972.
This progress is exactly what NASA was hoping for when the Apollo 17 astronauts—the last humans to set foot on the Moon—returned to Earth with more than 2,000 samples of lunar rock and dust. Some were squirreled away in the hopes that one day, better-equipped scientists could study the samples and make new discoveries.
And that’s what a team of researchers led by James W. Dottin III, an assistant professor of Earth, environmental, and planetary sciences at Brown University, just did. Dottin and his colleagues analyzed the composition of samples taken from the Moon’s Taurus-Littrow valley. The findings, published last month in the journal JGR Planets, indicate that volcanic material in the samples contain sulfur compounds that are starkly different from those found on our planet.
“Before this, it was thought that the lunar mantle had the same sulfur isotope composition as Earth,” Dottin said in a press release. “That’s what I expected to see when analyzing these samples, but instead we saw values that are very different from anything we find on Earth.”
A discovery 50 years in the making
After the Apollo 17 astronauts landed in the Taurus-Littrow valley, they extracted a 2-foot-long core sample from the lunar surface using a hollow metal instrument called a double drive tube. Once returned to Earth, this sample and many others like it remained sealed inside their tubes under the protection of NASA’s Apollo Next Generation Sample Analysis (ANGSA) program.
In the last few years, NASA has begun accepting new research proposals to study the ANGSA samples. Dottin proposed analyzing sulfur isotopes using secondary ion mass spectrometry, a high-precision technique that wasn’t available when the samples were first returned to Earth.
Researchers can use this technique to measure the ratios of different isotopes in a sample. These ratios serve as a distinctive “fingerprint” that points to the sample’s origin. Thus, two samples with the same isotopic fingerprint likely came from the same source.
Previous research has shown that oxygen isotopes in lunar samples are nearly identical between Moon and Earth rocks, so Dottin assumed the same would be true for sulfur isotopes. His findings tell a very different story.
Two distinct isotopic fingerprints
... continue reading