1. A recent study in 2025, based on NASA’s GRAIL (Gravity Recovery and Interior Laboratory) mission has found that the Moon’s nearside and farside are significantly different in terms of internal composition, temperature, and volcanic history.
2. The findings explain why the Moon’s Earth-facing side has vast dark plains, while the hidden side is mountainous.

KEY FINDINGS OF THE STUDY

 

A. Surface Differences
 

1. Nearsides: The side of the Moon facing Earth, known for its large, dark plains called “mare,” formed by cooled volcanic rock.
   • The nearside has thinner crust compared to the far side, allowing magma to rise more easily and form the flat plains of the mare.
2. Farsides: The farside is rugged, mountainous, and heavily cratered, with very few lava plains.
   • The far side has a thicker crust, which inhibited volcanic activity, leading to a more rugged, cratered surface.

 

B. Heat and Radioactivity
 

1. The nearside is warmer and geologically more active beneath the surface than the far side.
2. The presence of large volcanic plains on the nearside suggests that volcanic activity was more intense on this side billions of years ago.
3. Thorium and titanium, which generate heat through radioactive decay, are concentrated on the nearside.
4. This accounts for the higher temperature of the nearside mantle, which is about 100-200°C hotter than the far side.

 

How These Differences Are Explained:
 

1. Heat Distribution:
   1. The Moon's mantle, located between its crust and core, is responsible for around 80% of its mass.
   2. The presence of radioactive elements like thorium and titanium in the nearside mantle is the likely cause of its higher heat compared to the far side.
2. Tidal Deformation:
   1. The gravitational pull of the Earth on the Moon causes tidal deformation, a stretching of the Moon’s shape.
   2. This phenomenon occurs more on the nearside because Earth’s gravity pulls harder on this side, leading to the observed geological differences.

COMPARISON: NEARSIDE vs FARSIDE OF THE MOON : PRELIMS FACTS

 

Parameter	Nearside	Farside
Surface	Flat plains (mare)	Rugged and mountainous
Crust	Thinner	Thicker
Volcanic Activity	High (in the past)	Low
Radioactive Elements	High (Thorium, Titanium)	Low
Mantle Temperature	100–200°C hotter	Cooler
Tidal Deformation	Greater	Lesser

ABOUT THE GRAIL MISSION :

 

Full Form	Gravity Recovery and Interior Laboratory
Launched	2011
Launch Vehicle	Delta II rocket
Conducted By	NASA Jet Propulsion Laboratory (JPL), with MIT
Spacecraft	2 identical probes: Ebb and Flow
Objective	Create a high-resolution map of the Moon’s gravitational field
Methodology	Measured minute distance changes between the two probes to detect gravitational anomalies
Mission End	Concluded with a controlled impact on the Moon’s surface in 2012

SIGNIFICANCE OF THE STUDY
 

1. Confirms the role of radioactive heat and volcanic activity in shaping the nearside.
2. Reveals the asymmetric internal structure of the Moon.
3. Offers insights into thermal and geological evolution of the Moon.
4. Gravity maps will support the development of lunar navigation systems (like GPS).
5. Aids future lunar missions under programs like NASA’s Artemis and international collaborations.
6. The GRAIL methodology can be applied to explore other moons such as:
   1. Enceladus (Saturn): suspected to have a subsurface ocean.
   2. Ganymede (Jupiter): largest moon, potential for life.
7. The Moon helps stabilize Earth's axial tilt, crucial for climate stability.
8. It causes ocean tides, impacting marine and coastal systems.
9. Understanding the Moon helps understand Earth’s early history and habitability.

 

Also Read
FREE NIOS Books	UPSC Daily Current Affairs
UPSC Monthly Magazine	Previous Year Interview Questions
Free MCQs for UPSC Prelims	UPSC Test Series
ENSURE IAS NOTES	Our Booklist