Context: A payload onboard the Pragyaan Rover of Chadrayaan-3 mission has shared groundbreaking data on the Temperature profile of the south pole of the moon. 

Chandrayaan-3 

Chandrayaan-3 is a mission to demonstrate end-to-end capability in safe landing and roving on the Lunar surface. It consists of an indigenous Lander module (LM), Propulsion module (PM) and a Rover with an objective of developing and demonstrating new technologies required for Inter planetary missions.

• It consists of Lander and Rover configuration. 
• It will be launched by LVM3. 
• The propulsion module will carry the lander and rover configuration till 100 km lunar orbit. 
• The propulsion module has Spectro-polarimetry of Habitable Planet Earth (SHAPE) payload to study the spectral and Polarimetric measurements of Earth from the lunar orbit.

Lander Payloads

• Chandra’s Surface Thermophysical Experiment (ChaSTE) to measure the thermal conductivity and temperature.
• Instrument for Lunar Seismic Activity (ILSA) for measuring the seismicity around the landing site.
• Rambha Langmuir Probe (LP) to estimate the plasma density and its variations. 
• A passive Laser Retroreflector Array from NASA is accommodated for lunar laser ranging studies. 

Rover Payloads 

• Alpha Particle X-ray Spectrometer (APXS) and Laser Induced Breakdown Spectroscope (LIBS) for deriving the elemental composition in the vicinity of landing site.

ChaSTE (Chandra’s Surface Thermophysical Experiment)

ChaSTE is to study the heat conductivity of the Moon’s surface and measure the differences in temperatures at different points on and below the surface, with the overall objective of creating a thermal profile of the Moon.

• ChaSTE  has a temperature probe equipped with a controlled penetration mechanism capable of reaching a depth of 10 cm beneath the surface.
• The temperature probe is fitted with 10 individual thermal sensors.

Data Released

The graph released by ISRO illustrates the temperature variations of the lunar surface/near-surface at various depths, as recorded during the probe’s penetration.

• The first set of data released by ISRO showed a very sharp difference in temperatures just above and below the surface of the Moon.
• A graphical plot put out by ISRO showed that while temperatures on the surface were over 50 degree Celsius, they dropped to nearly -10 degree Celsius just a few millimetres below the surface.

• The measurements suggested that the topsoil of the lunar surface did not conduct heat very well, and insulated the sub-surface from heat.
• There were many indirect measurements done to know about the thermal profile of the Moon.
  • It was generally believed that the temperature on the moon’s surface was between 20 degree Celsius to 30 degree Celsius.
• ChaSTE is the first direct measurement of temperatures of the topsoil and the subsoil near the South Pole of the Moon.

Known Facts About Moon

• High Diurnal Range: The temperature on the moon can vary drastically between lunar days when the temperatures reach 120 degrees Celsius and reach -130 degrees Celsius during nighttime.
• Positioning of Sun: At the lunar South Pole, the Sun hovers below or just above the horizon, creating temperatures of 54 degrees Celsius during the sunlit period. 
• Deep Carter: Even during the day, the entire south pole is not lit by sunlight as the soaring mountains cast dark shadows and deep craters protect perpetual darkness inside the craters.
• Lack of Atmosphere: The reason behind the variation of day and night temperatures is the lack of atmosphere which does not block the Sun’s rays and leads to large variation in day and night temperature. 
• Change in Landforms: The lack of lunar atmosphere also means that craters and other landmarks do not erode like on Earth, leaving perpetual pockets of darkness near the moon’s poles that have the most frigid temperatures.

Benefits of Soil temperature Profiling of Moon’s south pole 

• Human Habitation: Help in understanding the moon’s composition, surroundings and direct search for water ice on the moon, which could support human habitation on the Moon in future.
• Human landing: Give an understanding of what kind of material can be used in varying temperature conditions and pave the way for future human landing.
• Selection of Material: Give insight into what material can be used on the lunar surface as the temperature gradient is very high that may lead to appreciable thermal expansion or contraction in materials and affect experimental set-up and other infrastructure.
• Material and associated exploration: Help in understanding the elemental composition of the moon, relative abundance of different materials and chemicals, the levels of radiation, and seismic activities.
• Identification of Rocky Areas: Reveals information about the lunar rocks as it takes longer to heat up and cool down than lunar soil, which could then allow scientists to identify rocky areas.
• Finding of Water Ice: Understanding the nature of the low-lying areas, that remain permanently shrouded in shadow and an ideal spot to maintain water ice.
• Habitation in Low Temperature Regions: Some craters remain permanently shadowed and haven’t seen sunlight in billions of years and experience temperatures as low as -203 degrees Celsius. In view of this, the ChaSTE has interesting facts to offer about the unexplored side of the lunar surface.

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