- By Geeta Pandey
- BBC News, Delhi
Photo of the Vikram lander taken by the Pragyaan rover
Last month, India made history when it became the first country to land a lunar mission near the South Pole of the Moon.
The Chandrayaan-3 lander and rover – called Vikram and Pragyaan – spent about 10 days in the area collecting data and images to be sent back to Earth for analysis.
Earlier this month, scientists put them to bed as the sun began to set on the moon – the lander needs sunlight to charge its batteries in order to function. The country’s space research agency Isro said it hopes to reawaken “around September 22”, when the next lunar day will occur.
Isro provides regular updates on their movements and findings and shares the images they have taken.
The updates excited many Indians, but others questioned the significance of the discoveries.
The BBC asked Mila Mitra, former NASA scientist and co-founder of Stem and Space, a Delhi-based space education company, to pick out some of the key findings of Chandrayaan-3 and explain their significance.
Distance covered – and craters avoided
Hours before the rover was put to bed on September 2, Isro said Pragyaan had “traveled more than 100 m (328 ft) and is continuing”.
That’s quite a long way for a six-wheeled rover traveling at 1cm per second.
What’s also important, Ms Mitra says, is that it was able to stay safe and avoid falling into the craters that cover the little-explored region of the moon’s south pole.
The rover, he says, has a special wheel mechanism – a so-called rocker bogie – which means all its wheels don’t move together, which helps it move up and down, but if it falls into deep terrain, it may not be able to climb out. crater. So it’s important to make it go around the craters or even go back. And that, Ms. Mitra adds, is being done by scientists at the command center who are “watching the moon through the eyes of the rover.”
“The rover is not automated and its movements are controlled from a control center that operates on the basis of transmitted images.
“There’s a little delay before they reach the command center because they’re taking a detour – Pragyaan sends them to the lander, which sends them to the orbiter to deliver them to Earth.
Isro released a graphic of the path traveled by the lunar rover
So by the time the command reaches the rover, it is a few steps closer to the threat.
But the fact that he managed to navigate safely past the two craters shows that he is able to communicate with the command center really quickly, Ms Mitra adds.
Hot and cold blowing
The first set of data collected from the lunar topsoil and down to a depth of 10 cm (4 in) below the surface from a probe aboard the Vikram lander showed a sharp temperature difference just above and below the surface.
While the temperature at the surface was nearly 60 °C, it dropped sharply below the surface, dropping to -10 °C at a depth of 80 mm (about 3 in) underground.
The moon is known for extreme temperatures – according to NASA, daytime temperatures near the lunar equator reach a boiling 120 °C (250 °F), while nighttime temperatures can drop as low as -130 °C (-208 °F). And temperatures of -250C (-410F) have been recorded in craters that never receive any sunlight and remain permanently in shadow.
But Ms Mitra says this big change in temperature is significant because it shows that the lunar soil – called lunar regolith – is a very good insulator.
“This could mean it could be used to build space colonies to keep heat, cold and radiation out. This would make it a natural insulator for habitats,” he says.
It could also be an indicator of the presence of water ice below the surface.
A clue to the evolution of the moon
When the laser detector mounted on the rover measured the chemicals present on the lunar surface near the south pole, it found a variety of chemicals such as aluminum, calcium, iron, chromium, titanium, manganese, silicon and oxygen.
But the most important of the findings, according to the scientists, concerns sulfur. “The first-ever in-situ measurement” by the instrument “unequivocally confirms” the presence of sulfur, Isro said.
The presence of sulfur on the moon has been known since the 1970s, but the fact that the rover measured sulfur on the lunar surface itself – and not inside a mineral or as part of a crystal – makes it a “tremendous achievement”, according to scientists.
Ms Mitra says the presence of sulfur in the soil is significant in many ways.
“Sulfur usually comes from volcanoes, so this will add to our knowledge of how the Moon formed, how it evolved and its geography.
“This also indicates the presence of water ice on the lunar surface, and since sulfur is a good fertilizer, this is good news because it can help grow plants if there is a habitable surface on the moon.”
Was it really a moonquake?
The Vikram lander carries an instrument that measures vibrations based on his own studies and experiments, as well as vibrations from the rover and its activities.
Isro said that while the Lunar Seismic Activity Instrument (Ilsa) had its ear on the ground, it also detected an “event that appears to be natural” and is investigating its source.
Isro said the lander recorded an event that “appears to be natural”
This event had a much larger amplitude, meaning it was much stronger, Ms Mitra says, adding that there could be several explanations for this.
“It could be some kind of space debris — like a meteorite or asteroid — hitting the surface. Or it could be seismic, which would make it the first lunar earthquake recorded since the 1970s. In that case, it could lead to an explanation of what is beneath the surface of the Moon and its geography.”
What is lunar plasma?
When Isro posted on X (formerly Twitter) that a lander probe had made the “first-ever measurement of the near-surface environment of lunar plasma” in the south polar region and found it to be “relatively sparse,” many wondered what that meant.
Ms Mitra explains that plasma refers to the presence of charged particles in the atmosphere that could interfere with the radio communications used by Chandrayaan-3.
“The fact that it’s very sparse or thin is good news because it means it will interfere much less with radio communications.”
When the lander jumped
The last thing the Vikram lander did before it was put to bed in early September was what Isro called a “hop experiment”.
The agency said the lander was “commanded to ignite its engines, rose about 40 cm (16 inches) and landed at a distance of 30-40 cm”.
This “successful experiment” means the spacecraft could be used to transport samples back to Earth or for human missions in the future, he added.
Could this short jump be a giant leap for India’s future space plans?
Ms Mitra says that “hop tested restarting the engine after landing on the moon to make sure it was still working well”.
It also demonstrated that the craft has “the capacity to take off in the lunar soil environment, as so far testing and actual takeoff has only been from Earth,” he adds.
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