Lunar Gravity Uncovers Moon’s Interior Differences
WASHINGTON – A detailed study of lunar gravity using data from two NASA robotic spacecraft sheds light on why the moon’s two faces—the one always visible from Earth and the one hidden away—look so different. The analysis of gravity data reveals the moon’s deep interior has an uneven structure shaped by intense volcanic activity on its near side billions of years ago.
The Gravity Recovery and Interior Laboratory (GRAIL) mission’s findings show that the moon’s near side flexes slightly more than the far side as it orbits Earth. This process, called tidal deformation, is caused by Earth’s gravitational pull and points to variations within the moon’s mantle, the thick geological layer beneath its crust.
Heat Differences in Lunar Mantle Explained by Lunar Gravity
According to the study, the moon’s interior is not uniform. The near side, facing Earth, is warmer and more geologically active deep inside than the far side. Vast plains called maria cover the near side, formed from ancient molten lava, while the far side features rugged highlands with few such plains.
Scientists have long suspected that volcanic activity concentrated radioactive, heat-producing elements like thorium and titanium on the near side’s mantle, driving these surface differences. The new gravity data offer strong support for this idea. Researchers estimate that the near side’s mantle is approximately 100 to 200 degrees Celsius hotter than the far side, likely maintained by radioactive decay.
Understanding Lunar Gravity and Its Role in Surface Features
The moon’s diameter is about 3,475 kilometers, roughly a quarter of Earth’s size. Beneath its crust lies the mantle, a layer 35 to 1,400 kilometers deep that accounts for almost 80% of the moon’s volume. Composed mainly of minerals like olivine and pyroxene, it resembles Earth’s mantle.
The detected asymmetry in the mantle matches the pattern of surface geology, particularly the abundance of volcanic rock known as mare basalt, which is about 3 to 4 billion years old. This suggests that the processes behind ancient volcanic activity still influence the moon’s interior today.
Gravity Data Advances Lunar Exploration and Science
The GRAIL mission’s Ebb and Flow spacecraft collected data over a year, producing the most precise gravity map of the moon to date. This enhanced lunar gravity map is essential for developing positioning, navigation, and timing systems crucial for upcoming lunar missions. These systems will help ensure safer and more reliable operations both in orbit and on the surface.
The methods used to study lunar gravity could also be applied to other celestial bodies, such as Saturn’s moon Enceladus and Jupiter’s moon Ganymede, which are key targets in the search for life beyond Earth.
Lunar Gravity Deepens Understanding of Earth’s Nearest Neighbor
The moon plays a critical role in stabilizing Earth’s rotation and generating ocean tides that affect natural cycles and daily life. While human and robotic missions have expanded our knowledge of the moon’s surface and interior, many mysteries about its deep structure and history remain.
As our closest celestial neighbor, the moon continues to be an important subject of scientific exploration, with lunar gravity studies providing new insights into its complex interior and geological evolution.
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