NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission has revealed why the Moon’s nearside and farside look so different. The findings, published in Nature, provide most detailed understanding yet of the Moon’s internal structure, heat distribution, and volcanic history.
Why Is Moon Asymmetric?
- Nearside: Faces Earth; dominated by smooth, dark volcanic plains (called “mare”)
- Farside: Rugged, mountainous, and heavily cratered
- This hemispheric asymmetry has long puzzled scientists.
About NASA’s GRAIL Mission
- Launched: 2011
- Spacecrafts: Ebb and Flow
- Objective: To create the most detailed gravitational map of the Moon
- Method: Measured minute variations in the distance between the two orbiting spacecraft to detect changes in lunar gravity
- Key Discovery:
- The Moon’s crust is thinner and more porous than previously thought
- Detected linear features called “dikes”, evidence of early expansion of the Moon’s surface
Key Scientific Findings
1. Tidal Deformation and Gravitational Influence
- The Moon’s nearside flexes more than its farside due to Earth’s gravitational pull
- This tidal deformation results in gravitational asymmetry, affecting the Moon’s internal structure
2. Volcanic Activity and Heat Distribution
- The nearside experienced more volcanic activity in the past
- Radioactive, heat-producing elements like thorium and titanium accumulated in the nearside mantle
- Result: The nearside is 100–200°C hotter than the farside, creating a thermal imbalance
3. Crustal Thickness Differences
- Nearside crust is significantly thinner, allowing magma to rise easily, forming vast lava plains
- Farside crust is thicker, leading to rugged, heavily cratered terrain
- Thinner crust also trapped radioactive elements, enhancing the long-term thermal difference
Significance of Findings
Future Lunar Missions:
- Understanding internal structure is vital for navigation, positioning, and timing systems (PNT) on the Moon
Exploration Potential:
- Findings can be applied to other celestial bodies like Enceladus (Saturn) and Ganymede (Jupiter), both candidates in the search for extraterrestrial life
Scientific Impact:
- Offers insight into the Moon’s geological history and evolution
- Helps us understand Earth-Moon dynamics and early solar system processes
Strategic Role of Moon:
- Influences Earth’s tides, stabilizes rotation, and impacts life on Earth