Chandrayaan-4 Lunar Sample Return: ISRO Finalizes 'Mons Mouton MM-4' Landing Site at Moon's South Pole for 2028 Launch

BENGALURU — Following the historic success of Chandrayaan-3’s soft touchdown at Shiv Shakti Point, the Indian Space Research Organisation (ISRO) has taken the next decisive leap in lunar exploration by finalizing the primary landing site and mission architecture for Chandrayaan-4—India’s first sovereign robotic lunar sample-return mission, slated for launch in 2028.

Following an exhaustive, two-year geomorphological and slope-stability evaluation utilizing ultra-high-resolution optical imagery and polarimetric Synthetic Aperture Radar (SAR) data from the Chandrayaan-2 orbiter, ISRO scientists have formally selected the Mons Mouton plateau (designated site MM-4) in the lunar South Pole region as the touchdown zone.

Chandrayaan-4 will attempt a complex, multi-stage engineering feat never before undertaken by the Indian space agency: drilling and collecting subterranean lunar regolith samples, launching an ascender rocket off the lunar surface, performing autonomous docking in lunar orbit, and returning the pristine samples safely through Earth's atmosphere.

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1. Why Mons Mouton MM-4? The Science Behind the Landing Site

Mons Mouton is a prominent, flat-topped lunar mountain rising several kilometers above the surrounding ancient impact terrain near the Moon's South Pole:

+-----------------------------------------------------------------------------+
|                 MONS MOUTON MM-4 LANDING SITE SPECIFICATIONS                |
+-----------------------------------------------------------------------------+
| Latitude / Longitude     | ~84.5° South / High Lunar Polar Region           |
| Surface Morphology       | Elevated plateau with low slope gradients (< 8°) |
| Solar Illumination       | Long periods of persistent sunlight for solar ops|
| Volatiles & Water-Ice    | Proximity to Permanently Shadowed Regions (PSRs) |
| Scientific Value         | Ancient South Pole-Aitken (SPA) basin regolith   |
| Hazard Distribution      | Minimal boulder fields and micro-crater density  |
+-----------------------------------------------------------------------------+

Because Mons Mouton borders ancient permanently shadowed craters containing subsurface water-ice deposits, the regolith samples gathered by Chandrayaan-4 will provide invaluable insights into the primordial composition of the Moon, the bombardment history of the early solar system, and the availability of in-situ resources for future human habitats.

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2. The Five-Module Architecture: A Masterclass in Space Engineering

Unlike Chandrayaan-3, which was a one-way landing mission, Chandrayaan-4 requires a sophisticated five-module stack, launched using two separate heavy-lift LVM3 rockets that will assemble in orbit:

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|                     CHANDRAYAAN-4 FIVE-MODULE STACK ARCHITECTURE            |
+-----------------------------------------------------------------------------+
| 1. Propulsion Module (PM) | Transfers the stack from Earth orbit to Lunar orbit|
| 2. Descender Module (DM)  | Performs powered descent and soft lunar landing |
| 3. Ascender Module (AM)   | Launches sample container from Moon back to orbit|
| 4. Transfer Module (TM)   | Captures Ascender, transfers sample container    |
| 5. Re-entry Module (RM)   | Heat-shielded capsule that enters Earth atmosphere|
+-----------------------------------------------------------------------------+

[ Dual LVM3 Earth Launches ] ──► [ Orbital Assembly ] ──► [ Trans-Lunar Injection ]
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[ Earth Splashdown / Recovery ] ◄── [ Lunar Orbit Docking ] ◄── [ Moon Touchdown & Drill ]

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3. The Drilling and Return Sequence

Once safely on the surface at Mons Mouton MM-4:

1. Robotic Drilling: A specialized core drill will penetrate 2 to 3 meters beneath the surface, extracting undisturbed stratified soil samples and sealing them in a hermetic vacuum container.
2. Lunar Surface Lift-Off: The Ascender Module will ignite its throttleable liquid engines, using the Descender Module as a launchpad to enter a 100-km lunar orbit.
3. Autonomous Orbit Rendezvous: In lunar orbit, the Transfer Module will perform autonomous optical docking with the Ascender, transferring the sample canister into the Re-entry Module.
4. Trans-Earth Injection: The Return stack will fire its engines to escape lunar gravity, trajectorying back to Earth for a parachute-assisted recovery in the Thar Desert or Bay of Bengal.

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4. Global Scientific Impact

Returning pristine lunar polar samples to Earth will allow Indian research laboratories, universities, and international space agencies to perform atomic-level mass spectrometry, isotopic dating, and mineralogical scanning that cannot be conducted by micro-instruments aboard rovers.

This mission cements India’s standing alongside NASA and China's Chang'e program as a tier-1 leader in deep-space planetary exploration.