Signals from seismic sensors left on the lunar surface by Apollo astronauts in the 1970s have revealed new insight into the moon's core, thanks to a fresh analysis using 21st century computing power.
The new study provides the first confirmation of layering of the moon's core and suggests that the moon, like Earth, has a solid inner core surrounded by a molten outer core, researchers said. But the moon's interior also has another layer of partially melted material – a ring of magma – around its outer core, the study found.
The findings come from data collected by four seismometers deployed on the moon by NASA astronauts between 1969 and 1972 during the space agency's six manned Apollo lunar landings. The seismometers kept working until 1977.
"The data itself has been in continual use since the Apollo era," said the study's lead author Renee Weber of NASA's Marshall Space Flight Center in Huntsville, Ala.
Most information about the composition of the center of the moon has been inferred from things such as its rotation, tidal distortion and magnetic field. However, there has been little hard data to draw on, researchers said. [10 Coolest New Moon Discoveries]
"The moon's deepest interior, especially whether or not it has a core, has been a blind spot for seismologists," explained Ed Garnero, a professor at the School of Earth and Space Exploration at Arizona State University, who also participated in the study. "The seismic data from the old Apollo missions were too noisy to image the moon with any confidence."
Weber, Garnero and their colleagues took advantage of an innovative new technique — originally developed to analyze earthquake observations on Earth — to provide the first direct information about the moon's core.
In addition to the lunar interior's layering, the study also suggests that the moon's iron-rich inner core contains less than 6 percent of light elements such as sulfur, researchers said.
The new research is detailed in the Jan. 7 issue of the journal Science.