India's Chandrayaan-3 unveils lunar secrets: Did the Moon once host a magma ocean?

India’s Chandrayaan-3 mission helmed by the Indian Space Research Organisation (ISRO) has unveiled groundbreaking insights about the Moon, shedding new light on its origins and geological history, particularly in the unexplored lunar south pole region.

The mission, which successfully placed the Pragyan rover on the Moon’s surface, has provided crucial data that has not only met but exceeded the scientific community’s expectations.

How was this find possible?

On August 23, 2023, India’s Chandrayaan-3 mission made history as its Vikram lander softly touched down on the Moon, specifically at 69.37°S latitude and 32.35°E longitude, a location now named Statio Shiv Shakti.

Soon after, the Pragyan rover, equipped with state-of-the-art scientific instruments, rolled out and began its exploration. Over the next ten days, Pragyan traversed approximately 103 metres of lunar terrain, methodically analysing the lunar soil at 23 different locations within a 50-metre radius of the landing site.

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The rover was equipped with the Alpha Particle X-ray Spectrometer (APXS) and the Laser-Induced Breakdown Spectroscope (LIBS), two instruments designed to measure the elemental composition of the lunar soil.

The APXS, developed by the Physical Research Laboratory (PRL) in Ahmedabad, used X-ray fluorescence spectroscopy and particle-induced X-ray emission to detect and quantify various elements in the soil.

By firing X-rays and alpha particles at the lunar surface, APXS recorded the characteristic X-ray lines of elements such as silicon (Si), magnesium (Mg), aluminum (Al), iron (Fe), calcium (Ca), and several minor elements, including sulphur (S), chromium (Cr), and titanium (Ti).

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The meticulous process of data collection involved stopping the rover at strategic points to allow the APXS to gather sufficient readings. The observation time at each location varied from 20 minutes to up to three hours, depending on mission requirements.

Over the course of the mission, APXS recorded a total of 31 hours of data, providing a comprehensive picture of the lunar soil’s composition near the south pole.

Did the Moon once house a magma ocean?

One of the most significant findings from Chandrayaan-3’s data is the strong support it provides for the Lunar Magma Ocean (LMO) hypothesis. This theory posits that the Moon was once entirely covered by a vast ocean of molten rock.

As this magma ocean cooled, it led to the formation of different layers within the Moon, including the crust, mantle, and core.

According to this hypothesis, the Moon’s crust is predominantly made of a rock type called ferroan anorthosite (FAN), which is rich in the mineral plagioclase. FAN is believed to have formed as the less dense plagioclase minerals floated to the surface of the cooling magma ocean, solidifying into the Moon’s outermost layer.

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Chandrayaan-3’s Pragyan rover detected significant amounts of FAN in the lunar soil near the south pole, a finding that aligns with previous missions like NASA’s Apollo and the Soviet Union’s Luna, which observed similar compositions in the equatorial and mid-latitude regions of the Moon.

The discovery of FAN in the south pole region is particularly crucial because it extends the validity of the LMO hypothesis to a new and previously unexplored area of the Moon. It confirms that the Moon’s crust, even in geographically distant regions, has a consistent composition, supporting the idea that the Moon’s surface was once a homogeneous ocean of magma.

Is this theory full proof?

While the detection of FAN reinforces the LMO hypothesis, Chandrayaan-3’s data also revealed the presence of magnesium-rich minerals in the lunar soil.

This finding introduces a little complexity to the LMO hypothesis, as it suggests that the lunar crust near the south pole is not composed solely of FAN but is instead a mixture of materials, including those from deeper within the Moon.

The presence of these magnesium-rich minerals is particularly intriguing because it implies that material from the Moon’s upper mantle may have been brought to the surface. This could have occurred during the formation of the South Pole-Aitken (SPA) Basin, the largest known impact crater in the solar system.

The SPA Basin, which is approximately 2,500 kilometres wide and 8 kilometres deep, is believed to have been formed by a massive asteroid impact around 4.2 to 4.3 billion years ago. This impact would have excavated material from deep within the Moon, potentially mixing it with the surface material and creating the diverse composition observed by Pragyan.

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The detection of magnesium suggests that the lunar soil at Statio Shiv Shakti is not just a simple remnant of the early lunar crust but also contains material from deeper layers, offering direct insight into the Moon’s internal structure and its evolutionary history.

This blending of materials from different depths could explain why the lunar soil near the south pole has a more complex composition than previously observed regions.

Why is this find by ISRO significant?

The findings from Chandrayaan-3 have significant implications for our understanding of the Moon’s geological history and its formation.

The data supports the idea that the Moon’s crust was formed from a global magma ocean, but it also suggests that subsequent events, such as the formation of large impact basins, have played a crucial role in reshaping the lunar surface and mixing materials from different depths.

This insight is critical for future lunar exploration, as it provides a more nuanced understanding of the Moon’s geological processes. The uniform composition of the soil observed by Pragyan also offers a valuable baseline for future remote sensing missions.

This consistency across different regions of the Moon suggests that the processes that shaped the lunar crust were global in nature, reinforcing the LMO hypothesis on a broader scale.

India’s Chandrayaan-3 mission has not only advanced our understanding of the Moon but has also positioned India as a key player in the global space exploration community. The mission’s success has been celebrated across the country, with Prime Minister Narendra Modi designating August 23 as India’s new ‘National Space Day,’ marking the day of the historic lunar landing.

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With inputs from agencies