Chandrayaan’s Pragyan rover presents evidence of magma ocean on young moon

A long night awaited the Pragyan rover on the moon as it bid farewell to Indian Space Research Organisation (ISRO) operators for the last time. The sub-zero temperatures proved too much for the suitcase-sized rover. Fourteen days after it landed on the moon as part of India’s historic Chandrayaan-3 mission, the rover went to sleep forever.

But in this window, the machine was already found All expectations of ISRO are fulfilled and accomplished its scientific goals. It spent two weeks studying the lunar soil and sent valuable scientific data back to Earth in anticipation of many discoveries – from recording Presence of Sulfur The presence of some small rock fragments has been confirmed around the crater rims near Shiva Shakti Bindu, the site where the Chandrayaan-3 lander landed.

Today, the Chandrayaan-3 team reported possibly its most important discovery yet, shedding light on the origin of the Moon.

one of Studies published In the journal Nature On August 21, the research team reported the presence of a rock called ferroan anorthosite in the lunar soil. The sighting is significant because it confirms what the US Apollo missions and the then Soviet Union’s Luna missions had seen from the lunar equator in the 1960s; Pragyan had worked in the south pole region of the moon. The consensus among scientists is that these anorthosite rocks could be remnants of an ancient ocean of magma that covered the surface of the moon about four billion years ago. Data obtained from Pragyan builds support for this idea.

Origin of the Moon

“Ferranean anorthosite rocks are very common on Earth,” Santosh Vadavale, principal investigator of Pragyan’s Alpha Particle X-ray Spectrometer (APXS) instrument and first author of the study, told this reporter. “In fact, all the anorthosite found on the Moon today is contributed by Earth.”

As is the consensus, the Moon was born from the remnants of a collision between the early Earth and some rogue planetary body. The Moon’s rocky surface was initially molten. As the lava cooled, the minerals in it slowly crystallized to form a variety of rocks, including ferroan anorthosite.

Meteorites raining down on the moon have reduced these rocks to dust over many centuries. Similar weathering events occur on Earth, but the moon has a much thinner atmosphere and no volcanic activity, so all meteorites that reach the surface are not deposited as new rocks over time.

The Vikram lander of the Chandrayaan-3 mission landed on the moon just after 6 pm Indian time on August 23, 2023. The Pragyan rover came out just a few hours later and remained about 100 meters away from Vikram for the next two weeks. The slow speed ensured that Pragyan did not collide with any stray rock or mountain, threatening the high-stakes mission.

During its journey, the rover occasionally stopped to observe the lunar dust with its instruments – from about 23 locations around the station Shiv Shakti. Its APXS instrument was mounted close to the rover Navigation camerasconfirmed the chemical and mineral composition of the dust by scanning it for X-rays and alpha particles produced by radioactive masses of curium.

Pragyan also paused for periods ranging from a few minutes to almost two hours to scan the soil. This is because dust particles often deflect alpha particles away from the APXS detector. Its pause helped the detector collect enough readings.

In these studies, Dr. Vadavale and his colleagues identified evidence of ferroan anorthosite as well as debris from another ancient debris scattered along the path of Pragyan.

Understanding the meaning of dust

Vikram’s landing spot, Station Shiva Shakti, is about 300 km from the solar system’s largest impact crater: the South Pole-Aitken basin. It is about 8 km deep and 2,500 km wide. Scientists have theorized that a powerful meteorite strike created the depression, causing material from inside the moon – perhaps from the upper mantle – to spread around the surface, possibly as far as Station Shiva Shakti.

Subsequent meteorite strikes on the Moon created a similar mix of this magnesium-rich material and anorthosite dust. Dr Vadavalle said he was relieved when the team found that Pragyaan’s data confirmed the unusually high magnesium content.

“What we’re finding matches very well with what the magma ocean was predicted and what the impact theory was,” he said.

He said such a feat would not have been possible with a normal orbiter mission. Orbiters can only identify the elements in the soil, not their abundance. The close-up view also helps in spotting details that the orbiter might miss simply because a certain part of the surface is not illuminated by the Sun. “In a normal orbiter scenario you don’t have full control over this.”

“So it’s important to actually get down to a surface and do a very detailed analysis there.”

He also said that Pragyan has established “ground truth” around the moon’s south pole, which can be ascertained from data already collected by past instruments, including the Chandrayaan-1 and Chandrayaan-2 missions. This requires some hard data tuning, which, Dr. Vadavale said, has already begun. “All our teams are already working on it, and then we will continue, and perfect it.”

While the rover itself has stopped working, data from its APXS and LIBS instruments still exist and could yield more science. “We hope to get some science from the APXS data itself. I mean, there are still some aspects of it that the teams are working on,” Dr. Vadavale said. “For example, the current paper is based on the overall bulk composition and all the major elements, but we have observations of many minor elementsAnd their concentrations. The expected changes in their concentrations also hold a certain key, so those aspects are still being worked on.