Chandrayaan-3: Why did Chandrayaan-2 lander fail? Why is it so difficult to land on Moon?

All eyes are set for the Chandrayaan-3 lunar mission on Friday, the Indian Space Research Organisation's (ISRO) high-profile launch of the year, aimed at achieving a soft landing on the Moon's surface. If successful, the ambitious endeavour will make India, the only fourth nation to have accomplished the challenging task after the United States, the former Soviet Union and China.

The mission comes four years after the ambitious Chandrayaan-2, which failed to achieve the desired soft landing in September 2019. It was meant to exhibit a range of capabilities, including reaching the moon’s orbit, making a soft landing over its south pole using a lander and subsequently, a rover studying the surface. (Chandrayaan-3 mission LIVE updates)

Also Read: Chandrayaan-3: A timeline of India's lunar exploration

Why did Chandrayaan-2 lander fail?

The ISRO’s ₹978 crore unmanned mission failed its objective after the lander ceased communication to the ground stations at an altitude of 2.1 km from the surface of the Moon. Soft landings, described by former ISRO chairman K Sivan, are “15 minutes of terror” which present a challenge due to the precise timing required for the rocket engine to fire. The firing attempts to “lower the lander carrying the rover down on the Moon, which has no atmosphere". This is why only 37% soft landings so far have been successful.

Why is it so difficult to land on the Moon?

Compared to the Earth, Moon’s reduced gravity, very little atmosphere and lots of dust pose difficulties in landing. The lunar south pole is an area of interest for humans due to the presence of water molecules. However, the surface also has hazards like rocks and craters, which can make it difficult to identify safe landing sites within shadowed and dark surface regions.

Also Read: ISRO's Chandrayaan-3 launch today: Streaming and timeline details

The ISRO explained that deep-space communication is also another challenge as the large distance from the Earth and the limited on-board and radio signals are weak with heavy background noises that need to be picked up by large antennas. Additionally, as the Moon’s location is continuously changing due to its orbital motion, the intersection of its path and Chandrayaan-3 have to be predicted sufficiently in advance with a high level of accuracy. Not only, the Moon’s reduced gravity a challenge, it is also ‘lumpy’ due to uneven mass distribution under its surface, making the attempt to orbit around the Moon a tough task, ISRO said.

During a soft landing, the variation in gravity has to be accounted for while charting the descent trajectory. The ISRO also said the lunar dust, which is negatively charged, sticks to most surfaces, causing challenges such as disruption in the solar pane and sensors’ performance. Temperature variations also make lunar environments hostile for lander and rover operations.