Chandrayaan-3 "Hop" Experiment reveals hidden lunar secrets as scientists uncover Regolith Heterogeneity at Moon’s South Pole

Chandrayaan-3 "Hop" Experiment reveals hidden lunar secrets as scientists uncover Regolith Heterogeneity at Moon’s South Pole

Chennai, May 19 (UNI) Proving a critial skill for future missions to bring unar samples back to earth, India's third Lunar Mission Chandrayaan-3's Vikram Lander performed 'Hop" Experiment that revealed hidden lunar secrets with the scientists uncovering

Regolith Heterogeneity at Moon’s South Pole.

These findings provide more insight for surface operations in the lunar southern polar region as understanding the local-scale heterogeneity (high diversity in surface characteristics within a short distance) is essential for future lunar exploration plans, especially for constructing scientific bases on the Moon.

This study marks the first of such class of unique measurements.

The Vikram lander of Chandrayaan-3 soft-landed on Moon’s surface on August 23, 2023. After having conducted experiments on the lunar surface, near-surface plasma, as well as ground vibrations for a period of around 10 Earth-days, the lander reignited its engines on September 02, 2023, to perform a "hop" by utilising the residual propellant.

This 'hop' proved a critical skill for future missions that will bring lunar samples back to Earth.To be scientifically accurate, it is note worthy that while we often call it 'lunar soil', the more apt term is the ‘lunar regolith’, which is actually 'shattered rock'- tiny, jagged

glass - like shards that are incredibly abrasive and cling to everything like static electricity, the Indian Space Research Organisation (ISRO) said on Tuesday.

Stating that uUnderstanding the thermal and physical (together referred to as ‘thermophysical’) properties of lunar regolith is important from both the scientific and technological perspectives, it said the ‘thermophysical characteristics’ of the regolith hold the clues to the question, how Moon manages the solar heat input; how much does it absorb, and how much is radiated back to space?

This is exactly what Chandra’s Surface Thermophysical Experiment (ChaSTE) did on the Moon. ChaSTE was a sharp-tip, rod-shaped probe, with temperature sensors mounted along its length, and a heater mounted at its tip, onboard the Vikram lander to penetrate the lunar regolith. The hop maneuver of the lander allowed ChaSTE to analyze a different location, observing how the engine plume eroded the lunar surface. This also helped acquiring measurements during the lunar twilight period (a person on the Moon would feel it is approximately 4:25 - 5:30 PM, seeing the relative position of the Sun with respect to the horizon; it is called the ‘local time’).

It is to be noted that a single day-night cycle on Moon lasts nearly a month on the Earth. This means 'twilight' on Earth is not a few-minutes-long sunset that we are habituated to see on Earth; it is, rather, a slow transition that lasts for hours, offering scientists an opportunity to watch the ground cool down in slow motion.

This opportunity enabled Physical Research Laboratory (PRL) scientists to derive the thermophysical, geotechnical characteristics and unique thermal response of the upper layer of the lunar regolith, at the high-latitude highland, where the Chandrayaan-3 landed, the Space Agency said.

The measurements by ChaSTE, particularly its penetration force and temperature profiles,indicated that the re-ignition of the lander engines resulted in erosion of the upper few centimetres of the regolith layer. This disruption led to the removal of the topmost “fluff” layer; a change that was directly captured in ChaSTE measurements, which was otherwise not observable.

Furthermore, the 3-D model simulations (software simulation to mimic the physical phenomena)supporting ChaSTE measurement using Chandrayaan-2’s OHRC high-resolution data, highlighted the complex structure of regolith with unique geo-technical and thermophysical properties. The top 2 to 6 cm regolith is found to be highly cohesive or ‘sticky’ and hyper-porous, which can act as

a thermal blanket. This layer is crucial in the storage of water-ice molecules in the subsurface, and in selecting the sites for future scientific base and habitat construction on the Moon.

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