The Moon is more colourful than you think. Here’s why
Artemis II crew spot green and brown patches ‘kind of like a piece of pie’
Nasa’s astronauts have reported seeing brown and green patches on the far side of the Moon.
During a lunar flyby on Monday, Nasa’s Artemis II crew saw “green hues” in the Aristarchus crater, and “a number of brown areas”.
The north-west corner of the lunar highlands had a brown tinge, according to the astronauts, something also seen near the Glushko crater and west of the Orientale basin.
Col Jeremy Hansen, one of the two mission specialists, said there was a “huge region” of brown that was shaped “kind of like a piece of pie”.
From Earth, the Moon usually appears a silvery-grey, unless eclipses, pollution, dust clouds or volcanic eruptions make it appear pink, orange or, occasionally, a bluey-green.
But experts said the surface of the Moon was “far more colourful” than commonly realised, because of metals and minerals in the lunar dust.
The green shades suggest the presence of titanium, or of olivine, the mineral that constitutes peridot gemstones. Brown patches are probably caused by iron oxide, also known as rust.
Dr Matthew Genge, of the Department of Earth Science and Engineering at Imperial College, said: “Although we generally see the moon in monochrome, close-up, a myriad of different colours are present.
“Hold a handful of lunar dust and look with a hand lens and there will be brown glass and green sparkling minerals. This kaleidoscope of colour merges together to make the greyed-out face of the Moon we are used to.”
The identification of multicoloured regolith, or lunar soil, on the far side of the Moon is not the first time astronauts have been surprised by the lunar surface.
During the Apollo 17 mission in 1972, Jack Schmitt, the astronaut and geologist, discovered vivid regolith in Shorty Crater in the Taurus-Littrow valley, saying: “There is... wait a minute... I see orange soil!”
Analysis of these colourful regions can lead to scientific breakthroughs. The orange Apollo 17 samples were found to be full of tiny glassy spherules with high iron oxide content that had been produced by some of the last volcanoes to erupt on the Moon around 3.64 billion years ago.
The discovery was critical in proving the Moon once experienced explosive volcanism, before falling silent.
In reports of scientific observations, Col Hansen told Nasa’s Mission Control: “We see a brownish hue and a greenish hue.
“I see those same brownish hues, west of Orientale and that’s a huge region, kind of like a piece of pie, with the point of pie pointing at Orientale then going up towards the northern side of Hertzsprung.”
Experts said observations of the surface made by Apollo astronauts were probably different from those of the Artemis II astronauts because the latter were much further away.
Prof Katherine Joy, of the Department of Earth and Environmental Sciences at the University of Manchester, said: “It gives you an indication that the Moon is far more than just many shades of grey – it’s a geologically complex planetary body.
“Colours on the Moon are controlled by what type of minerals or glass are present within the regolith that sits at the lunar surface, as well as how that area is illuminated in sunlight.
“The presence or absence of different colours could indicate what the local geology is like, or if a type of rock has been introduced to an area by an impact event.”
China’s Chang’e 6 Moon mission identified a “dark, greenish, and glistening” substance which could have been formed by moon dust melting into a green glass following a meteorite strike.
Green could also indicate a high level of titanium.
The next step is for the Artemis II science team to review all the astronauts’ descriptions and pore over the incoming higher-resolution images searching for the different features they have seen.
Dr Greg Brown, an astronomer at the Royal Observatory Greenwich, said: “It’s not surprising that the Artemis astronauts, being closer to the Moon than anyone has been in half a century, are seeing more from their vantage point than most have ever had the chance to.
“While we often think of the Moon as a very grey object as viewed from Earth, it is in reality far more colourful than we perceive it to be.
“Just as we see here on Earth, different rocks on the Moon with different chemical compositions have different colourations, leading lunar astronauts, and savvy astrophotographers, to see more colour than we would normally expect on the Moon.”
Dr Katherine Shirley, an expert in lunar geology and atmospheric physicist at the University of Oxford, said: “The observed browns and greens are likely related to the composition of the rocks on the surface. Brown is often associated with iron in the rocks and green could be attributed to the mineral olivine.
“These are common components of the type of rocks that make up the lunar mare and variations in the type and quantity of mineralogy could be an explanation for the colours. Of course, we will look forward to the official response from the Artemis science team.”
[Source: Daily Telegraph]
