Moon's Titanium Mystery Solved? IIT-Kharagpur Study Reveals Lunar Basalt Origins

Top Summary

• What happened: IIT-Kharagpur and PRL Ahmedabad researchers have offered an experimental explanation for the high titanium content in lunar basalts.
• Why it matters: The findings could inform the selection of landing sites for ISRO's Chandrayaan-4 mission in 2028.
• What changes: The study provides a deeper understanding of the moon's interior and volcanic history.
• Who is affected: Planetary scientists, ISRO, and future lunar missions will benefit from this research.

Unlocking Lunar Secrets: The Titanium Puzzle

The moon's surface is covered in ancient lava flows, distinctly different from Earth's. Lunar basalts contain unusually high levels of titanium dioxide (TiO₂), sometimes up to 18%, a long-standing scientific enigma.

A new study published in Geochimica et Cosmochimica Acta by researchers from IIT-Kharagpur and PRL Ahmedabad offers a compelling explanation.

Chandrayaan-4 Implications

ISRO's planned Chandrayaan-4 mission in 2028 aims to collect lunar rock samples for return to Earth. Selecting the optimal landing site is crucial for mission success.

 

"Regions near the lunar south pole, such as those being evaluated for Chandrayaan-4, including areas near Shiv Shakti region, have been studied in detail using data from Chandrayaan-2, NASA's Lunar Reconnaissance Orbiter, and other missions. What our work adds is a deep interior perspective." - Prof. Ghosh, IIT-Kharagpur

 

Himela Moitra, the study's first author, suggests that high-resolution cameras on landers can identify minerals. She also mentioned that instruments like X-ray fluorescence and X-ray diffraction can determine their chemical composition.

Tamalkanti Mukherjee added spectroscopic tools like Raman spectroscopy can further confirm mineral phases, similar to Mars missions.

The Ilmenite-Bearing Cumulate (IBC) Layer

Roughly 4.3 billion years ago, the moon was cooling from a molten state. The last layer to crystallize was the dense, iron- and titanium-rich ilmenite-bearing cumulate (IBC) layer.

The IBC layer sank into the lunar mantle and began to melt, creating titanium-rich partial melts, the suspected source of lunar basalts.

Recreating Lunar Conditions in the Lab

The researchers used a piston-cylinder apparatus at IIT Kharagpur, capable of pressures up to 3 GPa and temperatures of 1,500 °C.

They designed two experiments, one mimicking the IBC layer contacting the mantle, and another simulating chemical interaction during descent/ascent.

Reactions and Mixing

The tests indicated that high-titanium basalts resulted from complex reactions and mixing. The first experiment generated melts high in titanium but low in magnesium.

The mixed experiments produced basalts too high in magnesium and too low in titanium.

The team then simulated these processes on a computer. Some molten rocks could have directly erupted with moderate titanium levels. The titanium-rich rocks could have been trapped deep inside.

Two-Stage Model

The team's two-stage model reproduced the magnesium, titanium, silicon, and iron contents of high-titanium basalts. However, it underestimated aluminium and calcium oxide.

This model also explains prolonged volcanic activity by suggesting a repository of titanium-rich melts existed for billions of years.

 

"Indian laboratories, including those at IIT Kharagpur, PRL Ahmedabad, and other ISRO centres, have made significant progress in recent years...Our study demonstrates that high-pressure experimental work relevant to planetary interiors can now be carried out entirely within India, marking an important step toward building indigenous capability in planetary science." - Prof. Ghosh, IIT-Kharagpur

 

What to Watch Next

Future research will likely focus on refining the model to better account for aluminium and calcium oxide levels. Scientists will also analyze data from upcoming lunar missions like the European Space Agency's Lunar Volatile and Mineralogy Mapping Orbiter mission in 2028 to further validate the findings.