SOUTH KINGSTOWN – A University of Rhode Island scientist has used a series of experiments to determine the temperature inside the moon, providing crucial information about a scientific area that researchers know little about.
Experiments by Ananya Mallik, URI assistant professor of geosciences, indicate that the temperature at the boundary between the moon’s core and mantle to be between 1,300 and 1,470 degrees Celsius, or about 2,370 to 2,680 degrees Fahrenheit.
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The temperature at the moon’s surface is about minus 20 C, or about minus 4 F.
“In order to understand the interior structure of the moon today, we needed to nail down the thermal state better,” said Mallik, who joined the URI faculty last December. “Now we have the two anchor points – the core-mantle boundary and the surface temperature measured by [the Apollo missions] – and that will help us create a temperature profile through the moon. We need that temperature profile to determine the internal state, structure and composition of the moon.”
Mallik said the moon has an iron core, much like Earth, and previous research using seismic data had found that between 5 and 30 percent of the material at the boundary of the core and mantle was in a liquid or molten state.
“The big question is, why would we have some melt present in the moon at that depth?” Mallik said.
She conducted a series of experiments in 2016 at the Bavarian Research Institute of Experimental Geochemistry and Geophysics in Germany using a multi-anvil device that can exert the high pressures found deep inside the moon. Using a tiny sample of material similar to that found on the moon, she squeezed it in the device at 45,000 times the Earth’s atmospheric pressure, which is the pressure believed to exist at the moon’s core-mantle boundary. She then used a graphite heater to raise the temperature of the sample until it partially melted.
“The goal was to determine what temperature range would produce a 5 to 30 percent melt, which would tell us the temperature range of the core-mantle boundary,” she said.
With Mallik’s data, scientists can begin to develop a more precise temperature profile of the moon and proceed to determine a profile of the minerals inside the moon.
“It’s important that we know the composition of the moon to better understand why it has evolved as it has,” Mallik said. “The histories of the Earth and moon have been intertwined since the beginning. In fact, both are the product of a great collision between proto-Earth and an approximately Mars-sized body that occurred over 4.5 billion years ago. So, to understand our Earth better, we have to know our nearest neighbor because we all had a common start.”
William Hamilton is a PBN staff writer and the special projects editor. You can follow him on Twitter @waham or email him at hamilton@pbn.com.
