🗞️ Why in News ISRO identified Mons Mouton-4 (MM-4) — located at 84.289°S, 32.808°E near the Moon’s south pole — as the primary candidate landing site for Chandrayaan-4, India’s first lunar sample-return mission, using imagery from the Chandrayaan-2 Orbiter’s High Resolution Camera (OHRC).

What Is Chandrayaan-4?

Chandrayaan-4 is India’s fourth lunar mission, representing a qualitative leap from previous missions: it aims to land on the Moon, collect soil/rock samples (regolith), and return them to Earth — making India only the fourth country in the world to achieve a lunar sample-return (after the USA, Soviet Union, and China).

Mission profile (planned):

  • Land near the lunar south pole — a region of high scientific interest due to confirmed water-ice deposits in permanently shadowed craters
  • Collect ~3 kg of surface regolith samples
  • Return samples to Earth via an ascent vehicle docking with an orbiting return module
  • Total mission complexity: requires mastery of six critical technologies India has not yet demonstrated in combination: precision landing, sample collection, ascent from the Moon, rendezvous and docking in lunar orbit, re-entry, and Earth recovery

The Landing Site — Mons Mouton-4

Mons Mouton is a plateau formation (mons = mountain/highland in lunar nomenclature) located in the Moon’s south polar region. The MM-4 site at 84.289°S, 32.808°E was selected after analysis of:

  • OHRC (Orbiter High Resolution Camera) imagery from Chandrayaan-2 — which has been orbiting the Moon since 2019 and continues to produce data despite the Vikram lander’s crash
  • Terrain assessment by Space Applications Centre (SAC), ISRO, Ahmedabad — India’s primary remote sensing and space applications institution
  • Criteria: slope gradient (<15°), boulder density, sunlight availability for solar power, proximity to water-ice deposits

Why the south pole?

  • Permanently Shadowed Regions (PSRs) at the south pole contain water-ice — confirmed by Chandrayaan-1’s Moon Mineralogy Mapper (M³) instrument in 2008 and by ISRO’s ShadowCam analysis from LRO data
  • Water ice = potential in-situ resource for future crewed missions (drinking water, oxygen, hydrogen fuel via electrolysis)
  • Temperature in PSRs: ~40 Kelvin (–233°C) — among the coldest places in the solar system
  • Chandrayaan-3’s Vikram lander successfully landed at ~69°S on August 23, 2023 — Chandrayaan-4 targets a more challenging, higher-latitude site

The Chandrayaan Programme Progression

Mission Year Outcome
Chandrayaan-1 2008 Lunar orbiter; discovered water molecules on Moon via M³ instrument
Chandrayaan-2 2019 Orbiter (operational); Vikram lander crash-landed; Pragyan rover lost
Chandrayaan-3 2023 Successful landing at ~69°S; Vikram lander + Pragyan rover; first soft landing near south pole globally
Chandrayaan-4 Planned ~2028 Sample-return; first Indian sample-return mission

The Global Sample-Return Race

Chandrayaan-4 enters a competitive global landscape for lunar sample-return:

USA:

  • Apollo missions (1969–1972): Brought back 382 kg of lunar samples — still the benchmark for lunar science
  • Artemis programme: NASA targeting crewed return to Moon, including south polar landing

Soviet Union:

  • Luna 16 (1970), Luna 20 (1972), Luna 24 (1976): Three robotic sample-return missions; total ~300 grams returned

China:

  • Chang’e 5 (2020): Returned 1.731 kg of lunar samples from Mons Rümker (near equatorial region) — the first new lunar samples in 44 years; confirmed ~2-billion-year-old volcanic activity
  • Chang’e 6 (2024): First-ever sample return from the lunar far side (South Pole-Aitken Basin); returned ~1.9 kg

India’s challenge: Chandrayaan-4 will need to demonstrate rendezvous and docking capability in lunar orbit — a technology India is also testing with the SPADEX mission (Space Docking Experiment).

Key Technologies — SPADEX Docking Demonstration

The SPADEX (Space Docking Experiment) mission, launched December 2024, is India’s precursor technology demonstrator:

  • Two small spacecraft (SDX01 Chaser and SDX02 Target) launched together
  • Demonstrated autonomous rendezvous and docking in Earth orbit
  • Critical for Chandrayaan-4: the ascent vehicle leaving the Moon must dock with the orbiting return module to transfer samples

ISRO has confirmed that SPADEX’s success is a prerequisite for Chandrayaan-4 proceeding to full development.

UPSC Relevance

Prelims: Chandrayaan-4 (India’s first lunar sample-return mission), Mons Mouton-4 (84.289°S, 32.808°E), OHRC (Orbiter High Resolution Camera from Chandrayaan-2), Space Applications Centre (SAC), SPADEX (Space Docking Experiment), Chang’e 5 (China, 2020), Chang’e 6 (2024 — lunar far side), Apollo programme (382 kg), M³ instrument (Chandrayaan-1, water molecules 2008), Chandrayaan-3 landing date August 23, 2023.

Mains GS-3: Space technology — ISRO missions; lunar exploration; India’s space programme milestones; dual-use space technologies.

📌 Facts Corner — Knowledgepedia

Chandrayaan-4:

  • Mission type: India’s first lunar sample-return mission
  • Target landing site: Mons Mouton-4 (MM-4) — 84.289°S, 32.808°E
  • Site identification tool: OHRC (Orbiter High Resolution Camera) from Chandrayaan-2
  • Site assessment: Space Applications Centre (SAC), ISRO, Ahmedabad
  • Sample target: ~3 kg of lunar regolith
  • Planned year: ~2028
  • Prerequisite: SPADEX docking demonstration

Chandrayaan Programme:

  • Chandrayaan-1 (2008): Discovered water molecules via M³ instrument (Moon Mineralogy Mapper)
  • Chandrayaan-2 (2019): Orbiter (operational); Vikram crash-landed
  • Chandrayaan-3 (2023): Soft landing at ~69°S, August 23, 2023 — world’s first near-south-pole landing

SPADEX Mission:

  • Launched: December 2024
  • Purpose: Space docking demonstration in Earth orbit
  • Two spacecraft: SDX01 Chaser + SDX02 Target
  • Critical technology for Chandrayaan-4 lunar orbit rendezvous

Global Sample-Return Comparison:

  • USA Apollo: 382 kg returned (1969–1972)
  • China Chang’e 5 (2020): 1.731 kg from Mons Rümker
  • China Chang’e 6 (2024): ~1.9 kg — first from lunar far side (South Pole-Aitken Basin)
  • USSR: ~300 g (Luna 16, 20, 24 — 1970–1976)

Lunar South Pole Science:

  • Permanently Shadowed Regions (PSRs): Temperature ~40 Kelvin (–233°C)
  • Water-ice confirmed: Chandrayaan-1 M³ (2008); NASA LRO/ShadowCam
  • Water ice applications: drinking water, O₂ (breathable), H₂ fuel (electrolysis)

Other Relevant Facts:

  • ISRO headquarters: Bengaluru, Karnataka; founded 1969; Chairman (current): V. Narayanan
  • Artemis programme (NASA): crewed Moon return; Artemis III (first crewed landing, planned 2026)
  • India’s 4th country to achieve lunar orbit, 4th to soft-land on Moon (Chandrayaan-3), targeting 4th for sample-return
  • HLPST (High-Level Panel on Space Science and Technology): ISRO advisory body for mission prioritization

Sources: AffairsCloud, Drishti IAS