A team of scientists at National Aeronautics and Space Administration (NASA) have found that the moon has a core similar to Earth's.
The data sheds light on the evolution of a lunar dynamo -- a natural process by which our moon may have generated and maintained its own strong magnetic field.
Researchers previously had inferred the existence of a core, based on indirect estimates of the moon's interior properties, but many disagreed about its radius, state and composition.
The team's findings suggest the moon possesses a solid, iron-rich inner core with a radius of nearly 150 miles and a fluid, primarily liquid-iron outer core with a radius of roughly 205 miles.
The research indicates the core contains a small percentage of light elements such as sulfur, echoing new seismology research on Earth that suggests the presence of light elements -- such as sulfur and oxygen -- in a layer around our own core.
Where it differs from Earth is a partially molten boundary layer around the core estimated to have a radius of nearly 300 miles.
We applied tried and true methodologies from terrestrial seismology to this legacy data set to present the first-ever direct detection of the moon's core, said Renee Weber, lead researcher and space scientist at NASA's Marshall Space Flight Center.
Although sophisticated satellite imaging missions to the moon made significant contributions to the study of its history and topography, the deep interior of Earth's sole natural satellite remained a subject of speculation and conjecture since the Apollo era.
Future NASA missions are expected to gather more detailed data. The Gravity Recovery and Interior Laboratory, or GRAIL, is a NASA Discovery-class mission set to launch this year. The mission consists of twin spacecraft that will enter tandem orbits around the moon for several months to measure the gravity field in unprecedented detail.
The mission also will answer longstanding questions about Earth's moon and provide scientists a better understanding of the satellite from crust to core, revealing subsurface structures and, indirectly, its thermal history.
The Moon is Earth's only natural satellite and the fifth largest satellite in the Solar System. It is the largest natural satellite in the Solar System relative to the size of its planet, a quarter the diameter of Earth and 1/81 its mass.
The Moon is also the second densest satellite after Io and is in synchronous rotation with Earth, always showing the same face; the near side is marked with dark volcanic maria among the bright ancient crustal highlands and prominent impact craters.