• 5 months ago
Donc, la Lune rétrécit légèrement, ce qui peut sembler quelque peu alarmant au départ. Mais ne vous inquiézettez pas, la Terre n'est pas en danger à cause de ce rétrécissement lunaire. Ce processus provoque des tremblements de lune et des fissures à la surface, qui sont assez fascinants à étudier. Pensez-y comme à un raisin – à mesure que la Lune se refroidit, elle se ride et se contracte un peu. C'est un processus naturel qui se produit depuis très longtemps. Ces tremblements de lune ne sont nulle part aussi puissants que les séismes que nous ressentons ici sur Terre, donc ils ne représentent pas vraiment une menace. Mais est-ce que cela changera à l'avenir ? Animation créée par Sympa.
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Transcript
00:00Do not worry, but the moon is shrinking and writhing, a bit like a raisin that becomes dry.
00:08This happens because our natural satellite has kept its internal heat for more than 4 billion years.
00:15But its core is gradually cooling down and becoming denser.
00:19Unlike the soft skin of a raisin, the surface of the moon is quite friable.
00:24This fragility leads to the formation of cracks, where different sections of the crust meet against each other,
00:31giving rise to what scientists call moon tremors.
00:36So far, our satellite has shrunk by about 45 meters in circumference.
00:42This change is so minor that it does not affect the appearance of eclipses or phases of the moon.
00:48The tidal cycles will not be affected either, because the mass of the moon has not really changed.
00:55This shrinking process will not affect us directly here on Earth, but that does not mean that everyone is safe.
01:03The moon tremors caused by this shrinking process have been worrying researchers for years.
01:10During the famous Apollo missions, NASA astronauts left seismometers at different points on the moon.
01:17These devices were unable to detect the seismic activity of the lunar surface with exceptional precision.
01:26The equipment worked for several years and managed to record more than 12,000 lunar earthquakes with magnitudes ranging from 2 to 5.
01:36Until 1977, the team was able to identify four distinct types of tremors.
01:42Some, such as those caused by meteorite impacts, were relatively easy to isolate.
01:48However, the cause of superficial lunar earthquakes remains a mystery to scientists,
01:54which could be an obstacle for future lunar missions.
01:58As the name suggests, superficial earthquakes occur relatively close to the surface,
02:04most often from 50 to 220 km below the crust.
02:08Recent research suggests that these tremors would be triggered by the compression of the lunar surface,
02:13leading to the formation of overlapping cracks, where a layer of surface is pushed up and above another.
02:19This study also identified the epicenters of the most powerful earthquakes.
02:23It all started in the region of the South Pole, precisely where we want to settle.
02:29Our interest in the South Pole of the moon reached its peak in 2023,
02:33when the Chandrayaan-3 mission from India managed to land there and deployed a rover to explore the region.
02:40NASA also plans missions in this area, with the ambitious goal of sending astronauts there for the first time.
02:47The Artemis-3 mission, scheduled for 2026, identified 13 sites of potential lunar eclipses in the South Pole, represented here by blue squares.
02:57One of the options is inside a geological formation called Gerlach crater, a strategic area for exploration.
03:05This region could receive ice, because some parts remain permanently in the dark,
03:11while being close enough to the sunny areas, essential for collecting solar energy.
03:16The pink dots on this map indicate the most powerful epicenters of lunar eclipses recorded by the Apollo mission.
03:24This suggests that the clashes in this area could be relatively recent and active, posing a real danger for the Artemis-3 crew.
03:33The astronauts of this mission will stay in lunar orbit for 30 days, and two members will descend to the surface for about a week at the South Pole.
03:42Their exits will be particularly arduous, due to the extreme temperatures in these permanently darkened regions.
03:50The presence of lunar eclipses and potential landslides adds even more risk to this mission,
03:57because these phenomena are much more frightening than our Earthquakes.
04:02The most powerful lunar eclipse ever recorded had a magnitude of 5.7.
04:08This could seem insignificant compared to similar eclipses recorded in 2023 in countries like Chile,
04:15Colombia or Papua New Guinea, which did not cause major damage.
04:20But the situation is different on the Moon.
04:23As gravity is much lower than on Earth, a slight tremor can have much more striking effects,
04:29because you are not as solidly anchored to the lunar surface as you are to the Earth.
04:33Seismic waves can therefore cause larger movements on the surface.
04:40In addition, the duration of lunar eclipses is much longer.
04:43Our Earthquakes usually last between 10 and 30 seconds, some reaching sometimes two minutes.
04:49On the other hand, a lunar eclipse can last much longer.
04:53The Moon, being a solid, rigid and dry sphere, resonates powerfully when it is shaken,
04:59without any natural means of dissipating this energy.
05:02Lunar eclipses can last up to 10 minutes or more, with small shakes that last for hours.
05:10These new discoveries concerning lunar eclipses will not really change Artemis 3's potential landing sites or the duration of the mission.
05:20The reason for this is that precisely determining the frequency of eclipses in a specific region is an extremely complex task.
05:28Scientists know that these shallow eclipses are rare and pose a low risk for short-term missions to the lunar surface.
05:37However, the situation changes considerably when a long-term habitation is envisaged on the Moon,
05:43which could happen sooner than we thought.
05:47The Artemis 3 mission is a crucial step towards space colonization.
05:52China, on the other hand, plans to establish a permanent lunar base in the South Pole by 2040.
05:58Their strategy involves the use of 3D printing and the manufacture of bricks from the lunar soil in order to build this base.
06:06It is a fascinating prospect.
06:08But setting up such an infrastructure involves many challenges,
06:12including the management of intense cosmic radiations, lack of water and, of course, long-term Moon shakes.
06:22Over billions of years, the surface of the Moon has been bombed by asteroids and comets,
06:27causing the constant detachment of pieces and debris.
06:30As a result, the material on the surface is relatively soft and not compacted.
06:35When earthquakes occur, the slopes in these areas can be subject to landslides or the opening of new faults.
06:43Future colonies located too close to these unstable slopes could put their inhabitants at risk.
06:49The lunar dust adds another complication.
06:52Because without erosion or water for smoothing, it can become as hard as glass.
06:58To better understand the impact and risks of Moon shakes on future inhabitants,
07:03space agencies must map and collect new seismic data,
07:07not only in the South Pole, but on our entire satellite.
07:12In 2025, the FSS plans to deploy two of the most precise seismometers ever built in the Schrödinger crater,
07:23located on the hidden side of the Moon.
07:26Studying what is happening on this soil is crucial to understand the complex structure of the Moon and its internal dynamics.
07:34Scientists are still trying to determine whether the absence of seismic activity recorded on the hidden side of the Moon
07:40is due to an inability of current instruments to detect it,
07:44or to interference from fusion materials in the mantle.
07:48Once this question is clarified, it will be easier to understand the superficial shaking of the Moon
07:54and to assess their implications for the future colonies installed on our natural satellite.
08:01You may have heard that the Earth was also shrinking, but this is a different process.
08:06The Moon shrinks mainly because its core cools naturally.
08:10The core of the Earth also cools, but our planet has tectonic plates, unlike the Moon.
08:16Thus, the energy of the Earth's core moves its plates or frees itself through volcanic eruptions.
08:23The Earth also loses mass due to atmospheric loss.
08:27Our planet loses about 45,000 tons of mass per year,
08:31mainly due to our fleeing atmosphere.
08:34Indeed, Earth's gravity is not enough to retain light particles such as hydrogen and helium,
08:40which escape into space.
08:43However, these figures are not alarming,
08:46given that the atmosphere of our planet weighs more than 5 billion billion tons,
08:51or a figure of 15 zeros.
08:53In other words, it would take many times the current age of the universe for it to evaporate completely.
09:00I don't know about you, but I breathe more freely all of a sudden.

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