In an exciting milestone for lunar scientists around the globe, India’s Chandrayaan-3 lander touched down 600 km from the south pole of the moon on August 23, 2023.

In just under 14 Earth days, Chandrayaan-3 provided scientists with valuable new data and further inspiration to explore the moon. And the Indian Space Research Organisation has shared these initial results with the world.

While the data from Chandrayaan-3’s rover, named Pragyan, or “wisdom” in Sanskrit, showed the lunar soil contains expected elements such as iron, titanium, aluminum and calcium, it also showed an unexpected surprise – sulphur.

Planetary scientists like me have known that sulphur exists in lunar rocks and soils, but only at a very low concentration. These new measurements imply there may be a higher sulphur concentration than anticipated.

Pragyan has two instruments that analyse the elemental composition of the soil – an alpha particle X-ray spectrometer and a laser-induced breakdown spectrometer, or LIBS for short. Both of these instruments measured sulphur in the soil near the landing site.

Sulphur in soils near the moon’s poles might help astronauts live off the land one day, making these measurements an example of science that enables exploration.

Geology of the moon

There are two main rock types on the moon’s surface – dark volcanic rock and the brighter highland rock. The brightness difference between these two materials forms the familiar “man in the moon” face or “rabbit picking rice” image to the naked eye.

Scientists measuring lunar rock and soil compositions in labs on Earth have found that materials from the dark volcanic plains tend to have more sulphur than the brighter highlands material.

Sulphur mainly comes from volcanic activity. Rocks deep in the moon contain sulphur, and when these rocks melt, the sulfphur becomes part of the magma. When the melted rock nears the surface, most of the sulphur in the magma becomes a gas that is released along with water vapor and carbon dioxide.

Some of the sulphur does stay in the magma and is retained within the rock after it cools. This process explains why sulphur is primarily associated with the moon’s dark volcanic rocks.

Chandrayaan-3’s measurements of sulphur in soils are the first to occur on the moon. The exact amount of sulphur cannot be determined until the data calibration is completed.

The uncalibrated data collected by the LIBS instrument on Pragyan suggests that the moon’s highland soils near the poles might have a higher sulphur concentration than highland soils from the equator and possibly even higher than the dark volcanic soils.

These initial results give planetary scientists like me who study the moon new insights into how it works as a geologic system. But we’ll still have to wait and see if the fully calibrated data from the Chandrayaan-3 team confirms an elevated sulphur concentration.

Atmospheric sulphur formation

The measurement of sulphur is interesting to scientists for at least two reasons. First, these findings indicate that the highland soils at the lunar poles could have fundamentally different compositions, compared with highland soils at the lunar equatorial regions. This compositional difference likely comes from the different environmental conditions between the two regions – the poles get less direct sunlight.

Second, these results suggest that there’s somehow more sulphur in the polar regions. Sulphur concentrated here could have formed from the exceedingly thin lunar atmosphere.

The polar regions of the moon receive less direct sunlight and, as a result, experience extremely low temperatures compared with the rest of the moon. If the surface temperature falls, below -73 degrees C, then sulphur from the lunar atmosphere could collect on the surface in solid form – like frost on a window.

Sulphur at the poles could also have originated from ancient volcanic eruptions occurring on the lunar surface, or from meteorites containing sulphur that struck the surface and vaporised on impact.

Lunar sulphur as a resource

For long-lasting space missions, many agencies have thought about building some sort of base on the moon. Astronauts and robots could travel from the south pole base to collect, process, store and use naturally occurring materials like sulphur on the moon – a concept called in-situ resource utilisation.

In-situ resource utilisation means fewer trips back to Earth to get supplies and more time and energy spent exploring. Using sulphur as a resource, astronauts could build solar cells and batteries that use sulphur, mix up sulphur-based fertiliser and make sulphur-based concrete for construction.

Sulphur-based concrete actually has several benefits compared with the concrete normally used in building projects on Earth.

For one, sulphur-based concrete hardens and becomes strong within hours rather than weeks, and it’s more resistant to wear. It also doesn’t require water in the mixture, so astronauts could save their valuable water for drinking, crafting breathable oxygen and making rocket fuel.

While seven missions are currently operating on or around the moon, the lunar south pole region hasn’t been studied from the surface before, so Pragyan’s new measurements will help planetary scientists understand the geologic history of the moon. It’ll also allow lunar scientists like me to ask new questions about how the moon formed and evolved.

For now, the scientists at Indian Space Research Organisation are busy processing and calibrating the data. On the lunar surface, Chandrayaan-3 is hibernating through the two-week-long lunar night, where temperatures will drop to -120 degrees C. The night will last until September 22.

There’s no guarantee that the lander component of Chandrayaan-3, called Vikram, or Pragyan will survive the extremely low temperatures, but should Pragyan awaken, scientists can expect more valuable measurements.

Jeffrey Gillis-Davis is research professor of physics, Arts & Sciences at Washington University in St. Louis. This article is republished from The Conversation.

New Delhi:

What was known in theory has now been confirmed twice. The Chandrayaan-3 mission has authenticated the presence of sulphur on the lunar south pole region after on site tests, a historical first that could provide clues to the origins of the Moon and also have profound significance for space exploration, say scientists.

On Thursday, India’s space agency ISRO said the Alpha Particle X-ray Spectroscope (APXS) instrument onboard the Pragyan rover confirmed the presence of sulphur and some other elements in the lunar south. Before that, on Tuesday, ISRO announced that another instrument, the Laser-Induced Breakdown Spectroscope (LIBS), found sulphur in the region.

Also Read | ISRO’s Latest Video On Rover Roaming On Moon Has A “Chandamama” Reference

In line with expectations, ISRO also reported the LIBS instrument had detected aluminium, calcium, iron, chromium, titanium, manganese, silicon and oxygen.

“The elements found on the Moon are not merely isolated compounds. They are time capsules carrying the whispers of cosmic history. Such findings not only reshape our comprehension of lunar formations but also offer potential prospects for lunar exploration and habitation,” Akash Sinha, who was involved in developing software for the Pragyan rover, told PTI.

“One prevailing theory is that the sulphur may be trapped within water ice, implying that we might be on the brink of a monumental discovery: the physical presence of water ice on the moon,” the professor of practice at Shiv Nadar Institution of Eminence in Delhi-NCR added.

An old undated document from the US space agency NASA suggested the potential utilisation of sulphur for making lunar bricks or concrete using it with moon soil. Interestingly, China’s reported plans to test printing bricks from lunar soil this decade for constructing a permanent moon base align with this idea.

The revelation of sulphur’s presence might hold clues to the Moon’s composition and its volcanic past, scientists said.

“Surface sulphur comes from volcanic activity, indicating heavy volcanism at some point in the Moon’s history. However, the detection is from only one spot, so we need more data to gain a clearer picture,” said T V Venkateswaran, a scientist at Vigyaan Prasar, an autonomous organisation under the Department of Science and Technology (DST).

Sinha added that the discovery of sulphur represents a significant breakthrough in the understanding of lunar geology.

“The presence of sulphur, especially in an area where volcanic activity-a common source of sulphur-is notably absent opens up intriguing possibilities about the origins of the Moon,” he said.

According to astrophysicist Sandip Chakrabarti, the in-situ measurements definitively confirm sulphur’s presence in the region, a feat beyond the capabilities of the instruments on the previous Chandrayaan 1 and 2 orbiters.

“The compositions show abundant lighter metals such as aluminium and also abundant sulphur and iron. Sulphur could come from lunar volcanoes. Only traces of heavy metals such as titanium, and chromium, were found. These are along the expected lines,” Chakrabarti, director of the Indian Center for Space Physics in Kolkata, told PTI.

These elements, he explained, aren’t in their pure form and would need processing for future extraction.

“The discoveries made by Chandrayaan-3 hold vast implications for lunar exploration. Beyond the allure of space travel, the presence of these elements paints a vivid picture of the Moon’s character,” Chakrabarti reflected.

Experts also believe that aluminium’s lightweight strength could become a resource for future missions, potentially transforming the Moon into a launchpad for further space exploration. Calcium’s critical role in biological processes could fuel discussions about the Moon’s potential as a scientific research hub.

Chakrabarti expressed his enthusiasm for Pragyan’s contribution. “It is indeed heartening that Pragyan is actually sending the composition of the topsoil of the landing area, namely, Shiv-Shakti point.” He also highlighted the need for helium, hydrogen and water for future space travel, survival and power generation.

“Right now, we are concentrating on survival on the Moon and not getting richer,” he added.

ISRO has initiated a thorough investigation into the presence of hydrogen.

Venkateswaran, who is also a member of the outreach committee of the Astronomical Society of India, emphasised the rover’s role in confirming a finding from Chandrayaan-1 about hydrogen particles reflected by the Moon’s surface in 2008.

“We do need to see water in any of its forms and hydrogen. That would be a genuine achievement,” Chakrabarti added.

Chandrayaan-3 touched down on the lunar south pole on August 23, making India the first country to land on the uncharted surface.

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