Context: In a recent study, the research team has reported finding the presence of a rock type called ferroan anorthosite in the lunar soil. The findings are backed by the research from the Alpha Particle X-ray Spectrometer (APXS) placed in the Pragyaan rover.
Key facts about the Chandrayaan-3 Mission
- Chandrayaan-3 is a lunar exploration mission by ISRO which successfully demonstrated ISRO’s end-to-end capability in safe landing and roving on the Moon's surface.
- The follow-on mission to Chandrayaan-2 consisted of an indigenous propulsion system, lander module (Vikram) and a rover (Pragyan).
- On August 23rd, 2023, Vikram Lander made its historic touchdown on Moon and subsequently Pragyan rover was deployed.
- Landing spot: Vikram’s landing spot, named as Statio Shiv Shakti by the International Astronomical Union (IAU), is about 300 km from the largest impact crater (South Pole-Aitken Basin) in the solar system. It is around 8 km deep and 2,500 km wide.
- Major objectives:
- Demonstrate a safe and soft landing on the surface of the Moon
- Conduct rover operations on the Moon
- Conduct on-site experiments on the Lunar surface.
- Duration: Rover operated for one lunar day (roughly equals 14 Earth days). The lander and the rover have scientific payloads to collect samples of the moon and do in-situ experiments. The Vikram lander would transmit data back to Earth for comprehensive analysis by scientists.
- The Virtual Launch Control Centre at the Vikram Sarabhai Space Centre played a vital role in continuous real-time monitoring of the launch activities from SHAR.
- With the success of the mission, India joined the countries, the United States, Russia, and China to successfully land on the Moon.
Advanced instruments in Chandrayaan-3
Propulsion module:
- Spectro-polarimetry of Habitable Planet Earth (SHAPE) to gather data on the polarisation of light reflected by Earth to assist with exoplanet searches.
Lander payloads:
- Chandra's Surface Thermophysical Experiment (ChaSTE) to measure thermal conductivity and temperature on the surface.
- Instrument for Lunar Seismic Activity (ILSA) to detect Moonquakes.
- Radio Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere (RAMBHA) to measure the density of near-surface plasma, encompassing ions, and electrons, and monitor its temporal variations.
- Langmuir Probe to estimate the density and variation of plasma, or superheated gas, in the Moon's environment.
- Laser Retroreflector Array (from NASA) to measure distances using laser ranging to understand the dynamics of the Moon system.
Rover payloads:
The Pragyaan Rover was equipped with two primary scientific payloads designed to study the lunar surface in detail.
Alpha Particle X-ray Spectrometer (APXS):
- Function: To analyse the elemental composition of the lunar soil and rocks.
- Working:
- APXS emitted alpha particles towards the lunar surface which it produced from a radioactive mass of Curium.
- When these alpha particles interacted with the surface, they caused the atoms in the lunar material to emit X-rays. The energy of these X-rays is characteristic of the elements from which they originate.
- By detecting and analysing these X-rays, APXS determines the presence and abundance of various elements in the lunar soil, including light elements like magnesium and aluminium, as well as heavier elements like iron and titanium.
Laser Induced Breakdown Spectroscope (LIBS):
- Function: To examine the chemical and elemental composition of the lunar surface.
- Working:
- LIBS fires a high-energy laser pulse at the lunar surface. This laser pulse ablates (vaporises) a small amount of material from the surface, creating a plasma.
- The plasma emits light as it cools, and this light is analysed by the spectroscope. The specific wavelengths of light emitted correspond to the elements present in the material.
- By analysing the emitted spectra, LIBS identifies the elements present in the lunar soil, such as sulphur, aluminium, calcium, iron etc. This information is crucial for understanding the moon’s composition and geological history.
Key findings by the Pragyaan rover:
- Discovery of Sulphur: Pragyaan identified the presence of sulphur on the lunar surface. This finding is crucial because sulphur was not detected in this region by previous missions.
- Other Elements detected: Along with sulphur, the rover detected elements like aluminium, calcium, iron, chromium, titanium, manganese, silicon, and oxygen. These elements provide insights into the moon’s geological history.
- Presence of ferroan anorthosite: It reported the presence of a rock type called ferroan anorthosite in the lunar soil. The consensus among scientists is that these anorthosite rocks could be the remains of an ancient ocean of magma that blanketed the moon’s surface around four billion years ago. It also sheds the light on the moon’s origin.
- Ferroan anorthosite is a type of igneous rock that is composed primarily of plagioclase feldspar with a higher iron content.
The moon’s origins:
- The moon was born from the remains of a headlong collision between the early earth and some rogue planetary body aeons ago.
- The moon’s rocky surface was initially molten. The minerals in there slowly crystallised as the lava cooled to form rocks of various kinds, including ferroan anorthosite.
As the moon has a very thin atmosphere, all the meteorites raining down on the moon reach the surface and beat these rocks down to fine dust over many centuries.