Chandrayaan-3 detects ‘unexpected’ levels of sulfur on Moon: ScienceAlert

In an exciting milestone for lunar scientists around the world, India’s Chandrayaan-3 lander touched down 375 miles (600 km) below the moon’s south pole on August 23, 2023.

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

While data from Chandrayaan-3’s rover, called “Pragyan” or “knowledge” in Sanskrit, showed that lunar soil contains expected elements like iron, titanium, aluminum and calcium, it also revealed an unexpected surprise. – Sulphur.

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Planetary scientists like me know that sulfur exists in lunar rocks and soil, but only in very low concentrations. These new measurements suggest that sulfur concentrations may be higher than estimated.

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

Sulfur in the soil near the Moon’s poles could one day help astronauts stay away from the ground, making these measurements an example of science that enables exploration.

Geology of the Moon

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

The moon, with dark areas outlined in red, shows a face consisting of two ovals for eyes and two shapes for a nose and mouth.
The dark areas of the Moon have deep volcanic soil, while the bright areas have highland soil. (Everand6/Wikimedia Commons, CC BY-SA)

Scientists measuring the composition of the moon’s rock and soil in laboratories on Earth have found that the material in the darker volcanic plains contains more sulfur than the material in the brighter highlands.

Sulfur comes mainly from volcanic activity. The rocks present in the depths of the Moon contain sulfur and when these rocks melt, sulfur becomes part of the magma. When the molten rock comes close to the surface, much of the sulfur in the magma becomes a gas that escapes along with water vapor and carbon dioxide.

Some sulfur remains in the magma and remains within the rock after it cools. This process explains why sulfur is primarily associated with the deep volcanic rocks of the Moon.

Chandrayaan-3’s measurement of sulfur in soil is the first such measurement on the Moon. The exact amount of sulfur cannot be determined until data calibration is completed.

Uncalibrated data collected by the LIBS instrument on Pragyan suggests that the Moon’s highland soils near the poles may have higher sulfur concentrations than highland soils from the equator and possibly even higher than deep volcanic soils.

These preliminary results give planetary scientists like me who study the Moon new insights into how it works as a geologic system. But we still have to wait and see if the Chandrayaan-3 team’s fully calibrated data confirms the increased sulfur concentrations.

atmospheric sulfur formation

Measurements of sulfur are of interest to scientists for at least two reasons. First, these findings indicate that highland soils at the lunar poles may have fundamentally different compositions than highland soils in lunar equatorial regions. This compositional difference probably comes from different environmental conditions between the two regions – the poles receive less direct sunlight.

Second, these results suggest that there is somehow more sulfur in the polar regions. The concentrated sulfur here may have formed from the extremely thin lunar atmosphere.

The polar regions of the Moon receive less direct sunlight and, as a result, experience extremely low temperatures compared to the rest of the Moon. If the surface temperature falls below −73 °C (−99 °F), sulfur from the lunar atmosphere may collect into solid form on the surface – like ice on a window.

Sulfur at the poles may also originate from ancient volcanic eruptions on the Moon’s surface or from sulfur-rich meteorites that struck the surface and vaporized upon impact.

Lunar sulfur as a resource

Many agencies have thought about building some kind of base on the Moon for long-term space missions. Astronauts and robots could travel from the South Pole base to collect, process, store and use naturally occurring materials such as sulfur on the Moon – a concept called in-situ resource utilization.

In-situ resource utilization means fewer trips to Earth to obtain supplies and more time and energy spent searching. By using sulfur as a resource, astronauts can make solar cells and batteries that use sulfur, mix sulfur-based fertilizer, and make sulfur-based concrete for construction.

Sulfur-based concrete has several advantages over concrete commonly used in construction projects on Earth.

For one, sulfur-based concrete hardens and strengthens within hours rather than weeks, and it is more resistant to wear. It also doesn’t require water in the mix, so astronauts can save their precious water for drinking, creating breathable oxygen and making rocket fuel.

The Moon's gray surface is visible from above, with a box in the center indicating the rover's location.
Chandrayaan-3 lander, depicted as a bright white spot in the center of the box. The box is 1,108 feet (338 m) wide. (NASA/GSFC/Arizona State University)

While seven missions are currently operating on or near the Moon, the Moon’s south pole region has not been studied from the surface before, so Prajna’s new measurements will help planetary scientists understand the Moon’s geologic history. It will also allow lunar scientists like me to ask new questions about the formation and evolution of the Moon.

At the moment, scientists at the Indian Space Research Organization are busy processing and calibrating the data. On the lunar surface, Chandrayaan-3 hibernates during the two-week-long lunar night, where temperatures will drop to −184 °F (−120 °C). This night will continue till 22 September.

There is no guarantee that Chandrayaan-3’s lander component, called Vikram or Pragyan, will survive the extremely low temperatures, but if Pragyan wakes up, scientists can expect more valuable measurements.Conversation

Jeffrey Gillis-Davis, Research Professor of Physics, Arts and Sciences at Washington University in St. Louis

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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