The moon’s floor is covered by ancient lava flows which are usually completely different from these discovered on the earth. While volcanic rocks on the earth not often include greater than 2% titanium dioxide (TiO2), some lunar basalts — widespread volcanic rocks — carry as much as 18%, a undeniable fact that planetary scientists have struggled to clarify for many years.
A brand new examine by researchers from IIT-Kharagpur and the Physical Research Laboratory (PRL), Ahmedabad, printed in Geochimica et Cosmochimica Acta, has now provided an experimental account of how these titanium-rich basalts might have fashioned.
The examine’s authors had been Himela Moitra, Sujoy Ghosh, Tamalkanti Mukherjee, Saibal Gupta, and Kuljeet Kaur Marhas.
Cameras on landers
The Chandrayaan-4 mission, which the Indian Space Research Organisation (ISRO) has deliberate for 2028, goals to gather rock samples from the moon and return them to the earth, making the selection of touchdown website essential. The examine’s findings might assist inform that call.
Prof. Ghosh, one of the lead authors and affiliate professor at IIT-Kharagpur, stated, “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.”
According to the examine’s first creator Himela Moitra, “High-resolution microscopic cameras on landers can help identify minerals in lunar rocks, while instruments such as X-ray fluorescence and X-ray diffraction can determine their chemical composition before collection.”
“Spectroscopic tools such as Raman and visible-near infrared spectroscopy can help confirm the mineral phases in rocks before they are collected. Similar instruments have already been successfully used in Mars missions,” Tamalkanti Mukherjee, a PhD pupil at IIT Kharagpur and co-author of the examine, added.
The European Space Agency can be planning to launch its Lunar Volatile and Mineralogy Mapping Orbiter mission in 2028 to map the distribution of water and ilmenite on the moon.
Too excessive or too low
Roughly 4.3 billion years in the past, the moon was nonetheless cooling from a worldwide ocean of molten rock. In the method, olivine and orthopyroxene crystallised first, then plagioclase, which floated as much as type the moon’s pale crust. The final to crystallise was a dense, iron- and titanium-rich layer containing minerals referred to as clinopyroxene, ilmenite, and fayalitic olivine. Scientists name this the ilmenite-bearing cumulate (IBC) layer.
The IBC layer was too dense to remain put. Gravity pulled it downwards by means of the much less dense, magnesium-rich mantle in a course of referred to as cumulate overturn. As it sank into the warmer areas of the lunar inside, the IBC layer started to soften. The titanium-rich partial melts it produced are broadly considered the supply of the moon’s titanium-rich basalts — however the actual mechanism has remained contested.
When researchers beforehand tried to soften IBC rocks within the lab, the ensuing liquids didn’t match the basalts on the moon’s floor: they both didn’t have sufficient magnesium or had been too dense to rise and erupt as lava. The authors of the brand new examine got down to discover the lacking hyperlink.
They used a piston-cylinder equipment at IIT Kharagpur, succesful of exerting pressures as much as 3 gigapascals (GPa) of stress — equal to that beneath 700 km deep contained in the moon — and temperatures of 1,500 °C.
The team designed two units of experiments. In one set, they positioned a skinny layer of an artificial IBC layer above a layer of San Carlos olivine, a mineral on the earth that may be a good proxy for the moon’s magnesium-rich mantle, inside a capsule and subjected it to pressures of 1-3 GPa and temperatures of 1,075-1,500 °C. This setup mimicked the place the place a sinking IBC layer is available in contact with the mantle. In the opposite form of experiments, the team blended the 2 supplies collectively earlier than subjecting them to related situations, simulating a chemical interplay throughout a gradual descent or ascent.
‘Significant progress’
The outcomes of the checks urged that basalts excessive in titanium had been created in a fancy course of involving each reactions and mixing.
The first form of experiments generated melts containing 9-19% titanium dioxide however they had been stubbornly low in magnesium oxide, which is identical discrepancy older research had run into. The blended experiments produced basalts that had been too excessive in magnesium and too low in titanium, alternatively.
“Indian laboratories, including those at IIT Kharagpur, PRL Ahmedabad, and other ISRO centres, have made significant progress in recent years,” Prof. Ghosh stated. “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.”
When the team simulated a mix of these processes and outcomes on a pc, they discovered that some molten rocks might have risen straight and erupted with average quantities of titanium. Those rocks very wealthy in titanium might have nonetheless grow to be caught deep contained in the moon. Later, recent magma rising from under might have blended with these trapped pockets and the mixed molten mass might have erupted as lava wealthy in titanium.
Repository of melts
Per the examine, this two-stage mannequin might efficiently reproduce the noticed magnesium, titanium, silicon, and iron contents of the moon’s high-titanium basalts, however underestimated aluminium oxide and calcium oxide.
The mannequin might additionally clarify why volcanic exercise excessive in titanium continued all through the moon’s geological historical past quite than being confined to its earliest interval: as a result of the pure satellite tv for pc had a repository of titanium-rich melts in its inside for billions of years, ready for the correct situations to convey them to the floor.
mukunth.v@thehindu.co.in
Published – March 24, 2026 08:10 am IST
