What Happened
- Chandrayaan-3's Vikram lander performed a controlled "hop" experiment during the final phase of its mission on the lunar surface, reigniting its engines to lift off approximately 40 cm and relocate laterally by a similar distance before landing safely at a new spot.
- Before the hop, Vikram retracted its two deployed scientific instruments — ChaSTE (Chandra's Surface Thermophysical Experiment) and ILSA (Instrument for Lunar Seismic Activity) — along with the rover deployer ramp.
- After the hop and safe re-landing, all instruments were successfully redeployed and functioned as expected, demonstrating the feasibility of relaunching from the lunar surface.
- The hop experiment provided a second insertion point for ChaSTE, enabling a fresh set of thermal conductivity measurements at a new location within the landing zone.
- A new study published in Scientific Reports (2025) details the first in-situ thermal conductivity measurements of high-latitude lunar regolith using ChaSTE data from both before and after the hop.
Static Topic Bridges
Chandrayaan-3 Mission
Chandrayaan-3 was India's third lunar mission and the country's first successful soft landing on the Moon. It was launched by ISRO on 14 July 2023 and achieved a soft landing on 23 August 2023 near the lunar south polar region — making India the first nation to land near the Moon's south pole and only the fourth country overall to achieve a soft landing on the Moon.
- Launch vehicle: LVM3-M4 (Launch Vehicle Mark-3)
- Landing site: Near Shiv Shakti Point, ~69° south latitude, lunar south polar region
- Mission configuration: Propulsion module, Vikram lander, Pragyan rover
- Pragyan rover operated for approximately 14 days (one lunar day)
- Mission objectives: Safe and soft landing demonstration; rover roving on the Moon; in-situ scientific experiments
Connection to this news: The hop experiment was conducted after the primary mission objectives were complete, using Vikram's remaining fuel to demonstrate relaunching capability and collect an additional data point for surface characterisation.
ChaSTE — Chandra's Surface Thermophysical Experiment
ChaSTE is one of four scientific payloads on the Vikram lander. It consists of a thermal probe with ten temperature sensors placed at uneven intervals within a 10 cm depth range, designed to measure the temperature profile and thermal conductivity of the lunar regolith.
- ChaSTE measured thermal conductivity of lunar regolith at the landing site: approximately 0.0115 ± 0.0008 W m⁻¹ K⁻¹ (pre-hop) and 0.0124 ± 0.0009 W m⁻¹ K⁻¹ (post-hop)
- These are the first direct in-situ thermal conductivity measurements from the Moon's high-latitude southern region
- The very low thermal conductivity (comparable to loose, dry sand on Earth) confirms the highly porous, loosely packed nature of lunar regolith
- Active heating was performed at a depth of 80 mm to derive conductivity values
Connection to this news: The hop relocated ChaSTE to a new spot, providing a second independent measurement that corroborated the first, strengthening confidence in the data and revealing subtle spatial variability in surface properties.
Lunar Regolith
Lunar regolith is the layer of fragmented, unconsolidated material covering the Moon's bedrock, formed over billions of years by meteorite impacts, solar wind bombardment, and micrometeorite erosion. Its thermal and mechanical properties are critical for planning future crewed and robotic lunar missions.
- Typical regolith depth: 4–5 metres in mare regions, up to 10–15 metres in older highland areas
- Regolith at the south polar region is of particular scientific interest due to the possibility of water-ice in permanently shadowed craters
- Vikram's hop disturbed the top layer of regolith ("controlled excavation"), exposing the sub-surface structure and revealing a layered composition beneath the surface dust
- ISRO confirmed detection of sulphur (S) in the south polar regolith via the Laser-Induced Breakdown Spectroscopy (LIBS) instrument on Pragyan rover — the first such in-situ confirmation
Connection to this news: The hop's engine plume blew away the loose topmost regolith, exposing sub-surface layers and allowing scientists to compare the undisturbed surface with the freshly exposed material at the new landing point.
Sample Return and Future Lunar Missions
The hop experiment's primary technological demonstration — relaunching from the lunar surface with precision landing — is a critical capability for future sample return missions. Lunar sample return involves a lander collecting surface material, then a small ascent vehicle launching off the Moon to rendezvous with an orbiter for return to Earth.
- China's Chang'e-5 (2020) achieved the first robotic lunar sample return in 44 years, bringing back 1.731 kg of material
- NASA's Artemis programme aims to return humans to the Moon; crewed landers must be capable of ascent from the surface
- ISRO's Chandrayaan-4 mission (proposed) includes a sample return component, making the hop demonstration directly relevant to future mission planning
Connection to this news: By successfully reigniting engines and relocating on the lunar surface, Vikram proved that a lander can function as an ascent platform — a building block for India's own future sample return or crewed missions.
Key Facts & Data
- Chandrayaan-3 landing date: 23 August 2023; landing site: ~69°S latitude, near the lunar south pole
- Vikram hop height: ~40 cm; lateral displacement: ~40 cm
- ChaSTE thermal conductivity measurement: 0.0115–0.0124 W m⁻¹ K⁻¹ (extremely low, confirming porous regolith)
- Payloads on Vikram lander: ChaSTE, ILSA, RAMBHA-LP (Radio Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere), Shape (Spectro-polarimetry of HAbitable Planet Earth — passive NASA retroreflector)
- Payload on Pragyan rover: APXS (Alpha Particle X-ray Spectrometer), LIBS (Laser-Induced Breakdown Spectroscopy)
- Elements confirmed in south polar regolith by LIBS: Al, Ca, Fe, Cr, Ti, Mn, Si, O, S
- India is the 4th country to soft-land on the Moon (after USSR, USA, China) and the 1st to land near the south pole
- Chandrayaan-4 (proposed): sample return mission; LUPEX (Lunar Polar Exploration Mission) is a joint ISRO-JAXA mission planned for the south pole