Unraveling the mystery of billion-year-old specimens recovered from Apollo 17.

(Dan Tri Newspaper) - A small sample of the Moon, hidden for over 50 years, turns out to hold a big secret.

A sulfur crystal (Image: mineral vision/iStock/Getty Images Plus).

Shockwave detection

Scientists discovered troolite dust particles (mineral particles) collected by the Apollo 17 spacecraft in 1972. Accordingly, these objects may be as old as, or even older than, the Moon, a 4.5-billion-year-old relic of the early Solar System.

Planetary scientist James Dottin of Brown University (USA) couldn't hide his surprise: "My first thought was, 'Wow, this can't be true.' We had to double-check to make sure everything was correct, and it was. These are truly amazing results."

During the 1960s and early 1970s, NASA's Apollo astronauts brought back a total of 382 kg of lunar material to Earth. However, aware of future technological advancements, scientists sealed some rock samples for preservation, awaiting better study conditions.

One of these preserved specimens was studied by planetary scientist Dottin and his team, using mass spectrometry to determine the source of the sulfur in the sample.

Sulfur is a crucial element for understanding the geological history of an object. It can bind with metals like iron, travel between the core, mantle, and atmosphere of a planet, and retain isotopic traces of the environment in which it formed.

Isotopes are versions of an element with different numbers of neutrons. Their proportions in a material vary depending on how that material is made, a kind of "chemical barcode" that scientists can use to trace the origin, formation mechanism, and age of a sample.

Samples from Apollo 17's probe 73001/2 contained fragments of troilite, a compound of iron and sulfur commonly found in space.

Dottin and his team want to study the isotopic ratios of sulfur in troolites to learn more about the history of the Moon, particularly focusing on particles that appear to be of volcanic origin.

Astronaut Harrison Schmitt on Apollo 17 is using a sample collection instrument on the Moon (Photo: NASA).

Unexpected findings from sulfur-33

Some parts of the sample had slightly higher concentrations of sulfur-33, an isotopic pattern consistent with volcanic gas release, as predicted by Dottin and his team studying lunar volcanic rocks.

However, other parts of the sample showed the opposite: the proportion of sulfur-33 isotopes decreased significantly.

"Previously, it was thought that the lunar mantle had a sulfur isotope composition similar to Earth's," Dottin explained. "That's what I expected when analyzing these samples, but instead, we found values ​​that are very different from any we've found on Earth."

Scientists have never seen a lunar specimen with this isotope ratio, and there are very few ways it could have formed.

This level of sulfur-33 depletion suggests an interaction between sulfur and ultraviolet radiation in a thin atmosphere, raising two intriguing possibilities. Both suggest troilite is an ancient mineral.

Two hypotheses about the origin of ancient sulfur.

The first possibility is that sulfur formed on the Moon itself, around the time studies showed an ocean of magma covering the nascent Moon. As this ocean cooled and crystallized, sulfur-33 may have evaporated from the surface into the Moon's primordial atmosphere, leaving behind heavier isotopes.

The second hypothesis is even more intriguing. The leading hypothesis about the formation of the Moon is that the early Earth was struck by a Mars-sized object called Theia during the chaos of the early Solar System.

Some theories suggest that the resulting fragments remained in Earth's orbit, coalescing to form the Moon, while a portion of Theia disappeared into Earth's interior.

But parts of Theia may also remain on the Moon. And researchers suggest that its peculiar lunar sulfur may also have originated from Theia.

It's impossible to say which scenario is more likely, but we can consider the implications nonetheless. If the sulfur has been photochemically altered, that could be evidence of ancient material exchange from the Moon's surface to the mantle, Dottin said.

"On Earth, we have plate tectonics that do that, but the Moon doesn't," Dottin explained. "So the idea of ​​some kind of exchange mechanism on the early Moon is fascinating."

The presence of unusual sulfur could also refute the hypothesis that the Moon formed from radioactive dust from the Earth-Theia collision. If that were the case, the sulfur would be evenly distributed throughout the lunar mantle.

Planetary scientist James Dottin uses a secondary ion mass spectrometer to analyze lunar samples from Apollo 17 (Image: Brown University).

This is a promising discovery, and it's just a sample stored in a helium chamber since the 1970s. However, unraveling this mystery will likely require more samples from beyond Earth: from the Moon, from Mars, possibly even from asteroids, and we will need considerable time to collect them.

Whatever their origin, these particles hold the most peculiar and oldest trace of sulfur ever found on the Moon, a faint trace that leads us back to the very formation of the Solar System.

Source: https://dantri.com.vn/khoa-hoc/giai-ma-bi-an-mau-vat-hang-ti-nam-tuoi-lay-ve-tu-tau-apollo-17-20251126224829147.htm