Why in the News?

Scientists now believe the Moon’s near side looks different from its far side due to its internal structure and volcanic past, revealed by NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission.

About the GRAIL Mission:

• Launch: NASA launched the GRAIL mission in 2011 to study the moon’s internal structure.
• Spacecraft Used: It used two spacecraft, Ebb and Flow, flying in tandem to detect gravity variations.
• Objectives: The mission measured tiny changes in distance between the two spacecraft caused by differences in the moon’s gravitational field.
• Scientific Outcome: The data revealed important details about the moon’s crust thickness, interior composition, and subsurface features.

Key Findings: Reasons for the Moon’s Asymmetry

• Tidal Deformation: The nearside bends more than the farside due to Earth’s gravity, a process called tidal deformation.
• Internal Activity: The nearside is geologically warmer and more active, suggesting internal structural differences.
• Volcanic History: Ancient volcanic activity on the nearside formed large basaltic plains, while the farside remained rugged and less active.
• Heat Distribution: Elements like thorium and titanium accumulated on the nearside, making it 100–200°C hotter than the farside.
• Crust Thickness: The nearside has a thinner crust, allowing magma to escape, while the farside’s thicker crust trapped heat and blocked eruptions.
• Thermal Contrast: The thinner crust also allowed more heat-producing elements to concentrate, increasing the temperature gap between the two sides.

Why do these findings matter?

• Support for Lunar Missions: Insights from GRAIL help design better navigation and timing systems for future lunar operations.
• Applications: GRAIL’s method can be applied to other moons like Enceladus and Ganymede, which may hold potential for life.

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