The Moon is rusting (and we have to dust it off)

An electron gun to make moon dust

You have to think of everything before going back to the moon andconsider installing an inhabited base there. How to build buildings and insulate them from extreme temperatures? How to protect yourself from radiation and micrometeorites? How to produce water and oxygen? And most importantly… How to get rid of this awful and unbearable gray dust that sticks everywhere? The astronauts of the Apollo missions often complained about it: the lunar regolith, the rock dust that covers the surface of the star, is very fine, both sticky and abrasive. She clings to the suit without being able to dislodge it, stiffens her joints and damages her boots. It covers the solar panels and the visors of the helmets.

Astronaut Charles Conrad Jr picking up a rock sample, boots stained with dust, during the Apollo 12 mission in November 1969. Photo Nasa

In 2017, an American doctoral student worked for NASA on the design ofa combination that would repel regolith. Today, researchers at the University of Colorado at Boulder have a complementary new idea: what if we cleaned the dust with an electron beam? In a vacuum chamber, they carried out the test with a kind of electron gun on dusty surfaces… and the regolith flies away as if by magic. The negative charge of the electrons builds up on the target area, until the surface and dust “Repel each other” like magnets, explains Xu Wang, co-author of the study published in Astronautics Act.

Read also Colonization of the Moon: the special conquest

When the earth makes the moon rust

Not only is the Moon dusty, it rusts too! University of Hawaii planetologist Shuai Li recently delved into data recorded by the Indian probe Chandrayaan-1, which orbited the Moon for nine months in 2008-2009. And he noticed an interesting thing: in the polar regions, the light reflected from the surface of the Moon seemed to carry the spectral signature of thehematite, an iron oxide. We know that the Moon is full of iron rocks, but by what miracle were they able to oxidize, when there is neither liquid water nor oxygen on our satellite?

Mineralogical map of the Moon produced with the Indian probe Chandrayaan-1.  Areas in blue show water, concentrated (as ice) at the poles.  This is where the hematite was detected.Mineralogical map of the Moon produced with the Indian probe Chandrayaan-1. Areas in blue show water, concentrated (as ice) at the poles. This is where the hematite was detected. Image ISRO/NASA/JPL-Caltech/Brown University/USGS

Shuai Li requested NASA’s assistance to verify his find. “At first, I didn’t believe it, testifies Abigail Fraeman, geophysicist at NASA. It shouldn’t exist, because of the conditions on the moon. ” But after analysis, it confirms the presence of hematite on the Moon. It remained to explain its origin. A hint: there is more hematite on the visible side of the Moon than on its far side. The team led by Shuai Li therefore hypothesizes, this week in Science Advances, that oxygen traveled from Earth’s atmosphere to the Moon, along the tail of Earth’s magnetosphere. But is it recent, or very old? It will be necessary to measure the isotopes of oxygen in the lunar hematite to estimate its age. Oxygen could very well have approached the Moon when it was much closer to the Earth, a few billion years ago.

Tripled stars make tilted planets

Our solar system is simple, flat and well organized: all the planets orbit globally on the same plane. But how does this work in more complex systems, with three stars for example? Well, it’s a mess and the planets are going all over the place!

A team of astronomers described in the magazine Science of the week, the GW Orionis planetary system, which they managed to photograph with the Very Large Telescope in Chile. Located 1300 light years away, GW Orionis is still young. It has three suns and an immense cloud of dust which will gradually aggregate to give birth, in a few million years, to planets. This nursery is called the protoplanetary disc. However, astronomers discovered in the detailed photo of GW Orionis that his disk is twisted, and that it contains a dust ring with a completely different orientation. The proof: this ring casts a shadow on the rest of the disk around it.

On the right, the photo of GW Orionis showing the central ring separated from the protoplanetary disc, on which it casts a shadow.  On the left, artist's impression of the disc and the dust ring in 3D, from the photo.On the right, the photo of GW Orionis where we see the central ring separated from the protoplanetary disc, on which it casts a shadow. On the left, artist’s impression of the disc and the dust ring in 3D, from the photo. ESO / L images. Calçada, Exeter / Kraus et al.

“Any planet formed within the inclined ring will be characterized by a strongly inclined orbit around the star”, predicts researcher Alexander Kreplin from the University of Exeter in the United Kingdom, co-author of the study.

The vast majority of stars have a companion, even two or more. We will therefore not fail to observe other systems with planets orbiting on a very different plane. It only lacks a little technology to successfully observe them, because unlike the protoplanetary disk of GW Orionis, which reflects the light of its stars well, the planets already formed are dark and difficult to spot (we often guess the presence of exoplanets indirectly, by detecting movement or variations in the luminosity of their star). But Alexander Kreplin is confident: “We believe that we will be able to discover in the future many planets in oblique, very distant orbits, as part of planetary imaging campaigns, carried out using in particular the ELT.” L’Extremeley Large Telescope, European, is under construction in Chile and should come into operation around 2025.

Portrait in the sun of Comet Neowise

Comet Neowise passed closest to the Sun on July 3, 2020, at a distance of only 43 million kilometers… and it survived. “Other comets often break into several pieces, due to the thermal and gravitational stress undergone when approaching the Sun, recalls NASA. But this photo taken by Hubble shows that the solid core of Neowise apparently remained intact. ”

After being the star of the summer, parading in the night sky with enough light to be admired with the naked eye, with binoculars, and to be photographed by all the amateurs, the comet Neowise continues to be scrutinized by the professional instruments. The space telescope Hubble shot him the picture on August 8, zooming to the maximum. We cannot distinguish the matter (rock and ice) from the core, but we can distinguish the two jets of dust and gas ejected by the comet, which go in opposite directions. This gas cloud is 18,000 kilometers wide in the photo.

Photo of comet Neowise (C / 2020 F3) taken from the ground on July 16, 2020. In the insert, a Hubble photo taken on August 8, 2020 after the perihelion passage.Photo of comet Neowise (C / 2020 F3) taken from the ground on July 16, 2020. In the inset, Hubble photo taken on August 8, 2020 after the perihelion passage. Images Zoltan G. Levay & NASA, ESA, STScI, Q. Zhang (Caltech)


Camille Gevaudan

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