Chandrayaan-3: ISRO’s walk in uncharted territory of the Moon
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The Indian Space Research Organisation (ISRO) created history as Chandrayaan-3 spacecraft made a soft landing on the surface of the Moon on 23 Aug 2023 evening. The Vikram lander made the soft landing at 6.04 PM (IST), ending the disappointment over the crash-landing of the Chandrayaan-2 lander four years ago.
With the mission’s success, India has become the first country to land a spacecraft in uncharted territory near the lunar south pole. In fact, India is only the fourth country in history to complete a soft landing on the Moon after the United States, the Soviet Union and China.
According to ISRO, the mission’s three objectives are to demonstrate a safe and soft landing on the lunar surface, to demonstrate a Rover roving on the Moon and to conduct in-situ scientific experiments.
Soft landing simply means landing at a gentle, controlled speed to not sustain damage to a spacecraft. Amitabha Ghosh, a scientist for NASA’s Rover mission to Mars, explained it : “Imagine a spacecraft hurtling through space, at 10 times the speed of an airplane, having to nearly come to a standstill in order to land gently on the Earth — all in a matter of a few minutes and, more importantly, without any human intervention. This, in a nutshell, is a soft landing.”
Prime Minister Narendra Modi had announced from Bengaluru that the point where the Vikram lander touched down on the lunar surface would be named “Shiv Shakti” and the crash site of the failed Chandrayaan-2 mission in 2019 as Tiranga point.
Shortly after the Vikram lander landed and its health was assessed by the space agency, the dust settled on the lunar surface and the Pragyan rover rolled out of the lander. With this, the Chandrayaan-3 mission’s 14 days of science observations has begun. ISRO chief S Somanath added that ISRO will be working on a robotic path planning exercise that could aid future exploration of the Moon.
Why do scientists want to explore the lunar south pole?
Due to their rugged environment, the polar regions of the Moon have remained unexplored. But several Orbiter missions have provided evidence that these regions could be very interesting to explore. There are indications of the presence of ice molecules in substantial amounts in the deep craters in this region — India’s 2008 Chandrayaan-1 mission indicated the presence of water on the lunar surface with the help of its two instruments onboard.
In addition, the extremely cold temperatures here mean that anything trapped in the region would remain frozen in time, without undergoing much change. The rocks and soil in Moon’s north and south poles could therefore provide clues to the early Solar System.
Why hasn’t any spacecraft ever landed near the lunar south pole?
There is a very good reason why all the landings on the Moon so far have happened in the equatorial region. Even China’s Chang’e 4, which became the first spacecraft to land on the far side of the moon — the side that does not face the earth — landed near the 45-degree latitude.
It is easier and safer to land near the equator. The terrain and temperature are more hospitable and conducive for a long and sustained operation of instruments. The surface here is even and smooth, very steep slopes are almost absent, and there are fewer hills or craters. Sunlight is present in abundance, at least on the side facing the earth, thus offering a regular supply of energy to solar-powered instruments.
The polar regions of the Moon, however, are a very different, and difficult, terrain. Many parts lie in a completely dark region where sunlight never reaches, and temperatures can go below 230 degrees Celsius. Lack of sunlight and extremely low temperatures create difficulty in the operation of instruments. In addition, there are large craters all over the place, ranging from a few centimetres in size to those extending to several thousands of kilometres.
Why don’t some parts of the lunar polar regions receive any sunlight?
Unlike the Earth, whose spin axis is tilted with respect to the plane of the Earth’s solar orbit by 23.5 degrees, the Moon’s axis tilts only 1.5 degrees. Because of this unique geometry, sunlight never shines on the floors of a number of craters near the lunar north and south poles. These areas are known as Permanently Shadowed Regions, or PSRs.
In a 2019 report, NASA said, “Water that happens to find its way into PSRs may remain there for long periods of time. Data from the Diviner instrument onboard LRO (Lunar Reconnaissance Orbiter, robotic spacecraft currently orbiting the Moon) which measures temperatures across the Moon, including PSRs, indicate that some surfaces are cold enough so that water is stable at the surface.”
The Indian Space Research Organisation (ISRO) created history as Chandrayaan-3 spacecraft made a soft landing on the surface of the Moon on 23 Aug 2023 evening. The Vikram lander made the soft landing at 6.04 PM (IST), ending the disappointment over the crash-landing of the Chandrayaan-2 lander four years ago.
The Indian Space Research Organisation (ISRO) created history as Chandrayaan-3 spacecraft made a soft landing on the surface of the Moon on 23 Aug 2023 evening. The Vikram lander made the soft landing at 6.04 PM (IST), ending the disappointment over the crash-landing of the Chandrayaan-2 lander four years ago.