Moon's upper surface has two distinct layers within centimetres, reveals Chandrayaan-3 'hop' experiment

📌 Summary:

• Scientists from the Physical Research Laboratory (PRL), Ahmedabad, using data from Chandrayaan-3's 'hop' experiment, found the Moon's upper surface (regolith) is not uniform — a loose, porous top layer gives way to a denser, compact layer just 2-6 cm below

• The findings, published in the Astrophysical Journal, are based on the ChaSTE (Chandra's Surface Thermophysical Experiment) instrument; even at 6-9 cm depth the surface showed two distinct layers — a 'cake-like' structure

• On September 4, 2023, before hibernation, the Chandrayaan-3 lander fired its engines, lifted ~40 cm and landed again; the new study revises the 'hop' distance to about 50 cm (earlier estimate 30-40 cm)

• The rocket plume during the hop blew away ~3 cm of the top layer, exposing the layer beneath to ChaSTE, a temperature-sensor probe deployed for 57 minutes during the long lunar twilight

• The data is the first-of-its-kind thermal, density and layering profile of the Moon at twilight — useful for planning moon-walks, lunar bases and engine-firing close to the surface during return missions

• ChaSTE has yielded three major papers: earlier findings showed possible water-ice beyond the polar regions and a sharp temperature drop (~60°C cooler at just 10 cm depth), aiding plans for temperature-controlled lunar habitats

🎯 UPSC Relevance: GS3 — India's space science achievements, ISRO's scientific return from Chandrayaan-3 and the foundations being laid for future crewed and sample-return lunar missions.

📝 Prelims Facts:

• ChaSTE (Chandra's Surface Thermophysical Experiment) is one of four instruments on the Chandrayaan-3 lander (Vikram)

• Chandrayaan-3 soft-landed near the lunar south pole on August 23, 2023; the landing site is named 'Shiv Shakti Point'

• 'Regolith' is the layer of loose dust and broken rock covering solid bedrock on the Moon

• The findings were published in the Astrophysical Journal by the Physical Research Laboratory (PRL), Ahmedabad

🔑 Key Term: Lunar regolith — the unconsolidated layer of fine dust, soil and rock fragments produced by meteorite impacts that blankets the Moon's solid surface.