Les scientifiques disent que l'atmosphère terrestre pourrait "se gonfler" comme un ballon à mesure que la planète se réchauffe ! Lorsque l'air se réchauffe, il se dilate, ce qui signifie que l'atmosphère pourrait s'étendre plus loin dans l'espace. Cela peut sembler intéressant, mais cela pourrait perturber les satellites, les amenant à ralentir ou à dévier de leur trajectoire. Cette inflation se produit déjà en partie à cause du réchauffement climatique, et les experts pensent qu'elle pourrait s'aggraver si les températures continuent d'augmenter. La traînée supplémentaire sur les satellites rendrait les missions spatiales plus difficiles et plus coûteuses. C'est un rappel que même l'espace subit les effets de ce qui se passe sur Terre ! Animation créée par Sympa.
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FunTranscript
00:00About a year ago, an exceptional event took place on Mars.
00:04Its magnetic shield and the surrounding atmosphere expanded,
00:08reaching a size about three times higher than their usual dimension.
00:12The Earth has already witnessed a similar phenomenon,
00:15notably in 1989.
00:17This event has led to a spectacular expansion of our magnetosphere,
00:21reaching up to 100 times its normal size.
00:24Scientists warn that the Earth could once again experience such a situation.
00:29But on an even bigger scale.
00:31And the repercussions could be disastrous.
00:34Let's examine the reasons for this phenomenon
00:37and the consequences it could have.
00:39The space probe MAVEN, developed by NASA,
00:43has been orbiting Mars since 2014.
00:45This unique device is the only one to simultaneously monitor solar activity and that of Mars.
00:50On December 26, 2022,
00:52it witnessed a captivating event taking place on the Red Planet.
00:56The Martian atmosphere and its magnetic shield suddenly took on an unexpected magnitude,
01:01stretching for thousands of kilometers.
01:03According to scientists, such an event is of exceptional intensity and rarity,
01:08and MAVEN was able to capture it every moment.
01:10In trying to understand this anomaly,
01:12researchers have come up with a fascinating link.
01:15This phenomenon was directly related to solar wind.
01:19Solar wind is a flow of particles projected by our star,
01:22composed mainly of protons and electrons from the external atmosphere of our star,
01:27it moves at a dizzying speed,
01:29reaching 800 km per second.
01:32These charged particles propagate throughout the solar system in the form of plasma.
01:37Mars, just like the other planets in our solar system,
01:40is constantly exposed to this solar wind.
01:42Imagine it as a kind of continuous breath coming from our star.
01:47This wind exerts pressure on the Martian magnetic shield,
01:50called the magnetosphere,
01:51and contributes to the progressive erosion of the Martian atmosphere in space.
01:55Researchers have established that the huge expansion observed on Mars
01:59was due to a vacuum,
02:00unusual in the atmosphere.
02:03A fast solar wind caught up with a slower wind,
02:05causing a compression and thus creating a vacuum zone in the Martian atmosphere.
02:10This exceptional configuration triggered a fast and spectacular expansion of the magnetosphere.
02:16The Sun follows a cycle of about 11 years,
02:19alternating between a phase of low activity, called the solar minimum,
02:24and an intense phase of activity,
02:26called the solar maximum,
02:28before returning to its initial state.
02:31This phenomenon was observed in the 18th century,
02:34and we are currently in the 25th century.
02:37This cycle is linked to the magnetic field of the Sun.
02:40At the solar minimum, this field is powerful and structured.
02:43However, it weakens little by little,
02:45until the solar activity suddenly increases.
02:48This intensification generates solar winds,
02:51which project particles jets towards the planets,
02:54including the Earth.
02:55In 1999, the solar wind almost completely disappeared for three days,
03:00an event that could occur again soon.
03:03Scientists estimate this time that it could occur earlier
03:06and with an increased intensity.
03:08The Sun then becomes particularly active,
03:11releasing burning plasma,
03:13forming huge dark spots and emitting powerful radiation.
03:17And alas,
03:19the next solar maximum seems to have taken the scientific community by surprise.
03:23Initially planned for 2025,
03:26this solar storm seems to arrive faster than expected,
03:29taking scientists by surprise.
03:31The number of observed solar spots has far exceeded expectations.
03:34In 2022,
03:36the Sun reached a peak of solar spots over 8 years,
03:39followed, in 2023,
03:41by a doubling of the expected number of these formations.
03:43And that's not all.
03:45Solar eruptions also know a recrudescence.
03:48In March,
03:49a geomagnetic storm illuminated the skies
03:51with spectacular auroras visible in 30 American states,
03:55marking the most intense event of the last six years.
03:58Rare solar phenomena are also becoming more frequent.
04:01Among them,
04:02a huge plasma cascade,
04:04a polar vortex around the north pole of the Sun that lasted for hours,
04:08and a solar tornado extending over three days
04:11and culminating at a height equivalent to 14 times the diameter of the Earth.
04:15These growing solar activities pose risks for our planet.
04:19Solar storms can disrupt communications,
04:22damage electrical systems,
04:24cause power outages,
04:26and directly threaten living beings.
04:28They can also ionize the Earth's atmosphere,
04:31interfering with radio signals and GPS systems.
04:35If these disturbances coincide with natural disasters such as earthquakes or tsunamis,
04:40the consequences could be disastrous.
04:43In addition,
04:44powerful solar storms can generate electric currents
04:48capable of degrading essential infrastructures,
04:50such as electrical networks and railway lines.
04:53Aircraft passengers could be subjected to higher levels of radiation during solar storms.
04:59It is difficult to assess the exact consequences on their health.
05:03However,
05:04astronauts on board spacecraft,
05:06such as the International Space Station,
05:09could run much greater risks.
05:11Future missions will therefore have to integrate solar cycles into their planning.
05:16We are not the only species in danger.
05:18These storms can disrupt animal migrations,
05:21such as gray whales,
05:22sea turtles,
05:23and birds
05:24that rely on the Earth's magnetic field to orient themselves.
05:27And,
05:28cherry on the cake,
05:30the risk of potential collisions between satellites.
05:33Commercial space companies often favor the speed of launch to safety,
05:38thus neglecting the impact of space meteorology.
05:42During solar storms,
05:43the high ionized atmosphere exerts an increased drag on satellites in orbit.
05:48In the event of a problem,
05:49some could deviate from their trajectory and collide,
05:53or even fall back to Earth.
05:55The most impressive known solar storm is the 1859 Carrington event.
06:00This geomagnetic storm of unequal intensity
06:04illuminated the sky with visible auroras from the poles to Cuba and Japan.
06:09In the United States,
06:10their burst was such that gold diggers woke up in the middle of the night,
06:14thinking it was day.
06:15This storm was caused by a major solar eruption.
06:19Although the auroras were a breathtaking spectacle,
06:22their consequences were serious.
06:24The telegraphic systems of Europe and North America were disrupted.
06:29The pylons produced sparks,
06:32operators suffered electrical discharges,
06:35and equipment began to work thanks to the only auroral current,
06:39in the absence of batteries.
06:40Similar storms have occurred at least three times in history,
06:44causing the same devastation.
06:46Today, an event of this magnitude could cost between 600 and 2,600 billion dollars,
06:52just in the United States.
06:53Researchers will continue to analyze past events and data from ice cores,
06:58to better understand and anticipate the impacts of future solar storms.
07:02Although the behavior of our star remains unpredictable,
07:05it emphasizes the importance of deepening its study.
07:08The probability that the next storm will reach the intensity of a Carrington event is low.
07:13However, by taking advantage of this time to prepare,
07:17its effects could go unnoticed.
07:19Preparations generally consist of adjusting the trajectories of satellites,
07:23immobilize planes on the ground and locate sensitive infrastructures.
07:27During this time, we continue our exploration of Mars.
07:30The Martian atmosphere is very different from ours.
07:33On Earth, the air is breathable,
07:35mainly composed of nitrogen, oxygen and various other gases.
07:39However, the atmosphere of Mars contains extremely high levels of carbon dioxide.
07:45While on Earth, carbon dioxide accounts for less than 1%,
07:49on Mars, it accounts for about 96% of the atmosphere.
07:53In addition, the Earth's atmosphere is more than 100 times denser than that of Mars.
07:58Even though Mars is about twice as small as Earth,
08:01its atmosphere is incredibly thin, comparable to a pen compared to our air.
08:06However, it has not always been so.
08:09In the past, Mars could have looked like Earth.
08:12It turned out that it had water,
08:14and it was even possible that it was home to plants.
08:17If we added water to Mars today, plants could grow there.
08:21In the distant past, Mars experienced an intense period of volcanism,
08:25suggesting that it had a thick atmosphere and perhaps even a vast ocean.
08:29Although we do not know what happened to it, some theories exist.
08:33For example, although Mars has a magnetic field,
08:36it is very weak, which would have allowed the solar wind to sweep its atmosphere.
08:41Finally, it became the red, cold and dusty planet that we know today.
08:46NASA's Perseverance rover recently celebrated its 1,000th day on Mars,
08:51making remarkable discoveries.
08:53It crossed an ancient network of rivers and Martian lakes,
08:57collecting 23 precious samples.
08:59The latter will allow us to better understand the history and geology of the planet.
09:04Extreme phenomena, although intimidating,
09:06allow us to deepen our knowledge of the solar system.
09:10Fortunately, thanks to its robust design,
09:13MAVEN is able to resist violent solar storms,
09:16thus offering the opportunity to study Mars when it is deprived of its natural protection.