Vénus, le plus proche semblable de la Terre, possédait autrefois des océans et des lacs semblables à ceux de la Terre, mais c'est maintenant un lieu extrêmement chaud et pressurisé. La raison principale en est que Vénus est plus proche du soleil, recevant plus d'énergie, ce qui a rendu son atmosphère beaucoup plus harsh au fil des milliards d'années. Contrairement à la Terre, Mars a perdu son atmosphère primitive car sa taille plus petite ne pouvait pas la retenir, notamment après que l'activité volcanique se soit ralentie et arrêtée. Vénus, étant si proche du soleil, a vu ses océans s'évaporer, et les volcans ont continué à émettre du dioxyde de carbone, un puissant gaz à effet de serre. Les océans de la Terre aident à contrôler le dioxyde de carbone en l'absorbant et en le transformant en roche, raison pour laquelle il est si important de les protéger. Animation créée par Sympa.
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FunTranscript
00:00Venus and Earth are so different, that a question as absurd as
00:05What is the longest?
00:07A day or a year?
00:09Which would have no meaning on Earth
00:11takes all its meaning on our neighbor
00:13Indeed, a day on Venus is longer than a year
00:17To put this in perspective
00:19a Venusian day is equivalent to 243 Earth days
00:23while a Venusian year lasts only 225 Earth days
00:27It's as if you were celebrating your birthday every day
00:30Venus is often nicknamed the malefic twin of Earth
00:34Their differences are so striking
00:36that one could think they come from totally different galaxies
00:40To give you an idea of their divergence
00:42if the year-day ratio was not enough
00:45the sun rises to the west on Venus and sets to the east
00:48One of the rare similarities between these two planets is their size
00:52However, there was a time when Venus and Earth were knitted like ass and shirt
00:56the best friends since the beginning of the solar system
01:00Venus was once the center of all attention
01:03NASA scientists think it could have sheltered a liquid water ocean
01:07and surface temperatures suitable for life for up to 2 billion years
01:12But the current Venus is quite different
01:14with its extreme temperatures and a dense atmosphere of carbon dioxide
01:19So, what led to this cosmic relooking?
01:22The size, location and latitude
01:25In other words, the distance from the sun and the internal heat of the planet
01:29which played a crucial role in the destinies of Venus and Earth
01:33By the way, it was a time when three planets could potentially shelter life
01:38Venus, Earth and Mars
01:41Imagine three cakes in an oven
01:43Once cooked, it would be time to take them out
01:46One would have been placed in front of an open window in the middle of winter
01:49another carefully placed on a table and covered with a nice clean torch
01:54and the last one would have simply been forgotten in the oven
01:57Mars, Earth and Venus are like these three cakes
02:01Mars has become too cold and inhospitable
02:04Earth has remained pleasant and tempered
02:06well protected from most of the unpleasantness
02:09just like the lucky cake protected by its torch
02:12and Venus has become hot and clean and edible
02:15In terms of development, Earth has followed a slow and regular path
02:20Preserving its oceans, its stable atmosphere and its biodiversity
02:24Venus, on the other hand, has increased its temperature
02:27seen its oceans evaporate
02:29and did not lean on greenhouse gases
02:32As a result, we have a planet where you melt faster than a snowman in July
02:37Mars, on the contrary, would turn you into ice in a few seconds
02:41However, it could have been quite welcoming
02:45Some scientists think that Mars was once covered with rivers and lakes in abundance
02:50and that it certainly did not lack water
02:53Even today, Mars still has the remains of an ocean called Oceanus Borealis
02:59This ocean has lost almost all its water over time
03:02Now, the Martian water sources include the ice caps of the poles
03:06and the minerals present in the rock
03:09According to estimates, only 1% of all this water has evaporated
03:13while 99% are still prisoners of the red planet
03:17The polar ice caps are easy to apprehend since we have the same on Earth
03:22But rocks containing water?
03:24It's simple
03:25There are at least 4 types of hydrated minerals on Mars
03:29There are hydric clay composed of silicon and oxygen
03:33and what is interesting is that they can also contain magnesium and iron
03:38which decline under the form of hydrated sulfates
03:41Do not be offended if you are told that all this releases a strong smell of rotten eggs
03:46but it is typical of hydrogen sulfide and not just sulfur
03:50These minerals directly integrate water into their chemical formula
03:53We also find hydrated silica, whose formula also contains water
03:58Scientists have experimented with plant culture in conditions similar to those of Mars
04:03and have achieved some success with alfalfa
04:05The culture of alfalfa has also helped to accelerate the growth of other plants
04:09such as turnips and lettuce
04:11Although water can be available on the red planet
04:14the air on Mars is mainly composed of carbon dioxide
04:18However, the in-situ experience of Mars oxygen resources
04:23or simply MOXIE, can produce oxygen on Mars
04:26which could be crucial for future missions
04:29Regarding the Martian energy sources
04:31solar, wind and geothermal energies are among the most promising
04:36Solar energy is less effective on Mars due to lower light and frequent sand storms
04:42but wind and geothermal energies could serve as an alternative
04:46With these resources available, humans could potentially thrive on Mars
04:51But let's go back to the comparison of our sister planets
04:55While Mars and Earth have moons, Mars even having two
04:59Venus has none, just like Mercury
05:02Due to its proximity to the Sun and the gravitational attraction of our star
05:07Mercury cannot retain satellites
05:10The probability that a moon orbiting Mercury will collide with the planet
05:15or be attracted to the orbit of the Sun would be high
05:19All this seems pretty obvious
05:21However, the absence of moons around Venus remains an unsolved enigma
05:26Despite the extremely high temperatures of Venus
05:29scientists think that even today
05:32it could not be as hostile to life as we thought it was before
05:36A recent study by MIT discovered 19 amino acids
05:40that survived a whole month in a solution comparable to what we find on Venus
05:45Yes, some people like it when it's spicy
05:48In addition, Rocket Lab and the Massachusetts Institute of Technology
05:52have teamed up to send a non-inhabited spacecraft
05:55the Venus Lifefinder, on an exploration mission
05:58This spacecraft will search for signs of life in the Venusian atmosphere
06:02using a special instrument called a self-fluorescent nephelometer
06:06And no, we're not inventing anything
06:08Initially planned for launch in 2023
06:11the mission was postponed to December 2024
06:14with an arrival in the orbit of Venus planned for May 2025
06:19The objective of the mission is to discover organic compounds
06:22in the atmosphere of the planet
06:24which could indicate the existence of habitable conditions
06:27in its cloud layer
06:29The spacecraft is equipped with a stage of cruises called Photon Explorer
06:33and a compact atmospheric probe equipped with a nephelometer
06:37The probe will descend through the Venusian atmosphere
06:39collecting data on cloud particles and organic compounds
06:44In 2020, scientists announced the discovery of phosphine on Venus
06:48a compound potentially linked to life
06:51They are still working to confirm this discovery
06:54using data from telescopes or even previous missions
06:58It could be that evidence is hidden in the old data
07:01received from Venus by NASA
07:03which could bring more clarity on this discovery
07:07The possible presence of phosphine on Venus
07:09has aroused both enthusiasm and caution among scientists
07:13To confirm this hypothesis
07:15more data from telescopes or new space missions are necessary
07:20If this gas is actually detected
07:22it could indicate the existence of a form of life
07:25producing phosphine in the clouds of Venus
07:28thus marking a big step towards a better understanding of the planet
07:32Some experts estimate that sending probes to Venus
07:35to detect phosphine directly
07:37would be the most reliable method to confirm its presence
07:41It could even be that a NASA mission from the 80s
07:45has already detected this phosphine
07:47but that this discovery was unnoticed at the time
07:51Today, the data is re-evaluated
07:53to identify any negligible evidence of the presence of this gas
07:57This could also indicate that phosphine
07:59has been present in the atmosphere of Venus for decades
08:02raising questions about its origin
08:05However, this interpretation is not unanimous
08:08and a debate has been engaged among scientists
08:11about the real nature of the gases detected
08:13The old data from other missions
08:15could also provide clues
08:17about the presence of phosphine on Venus
08:20While new space machines are about to explore the planet
08:24the key to solving this mystery
08:26could well be found in archives
08:28that are several decades old
08:30To date, 46 space missions have been sent to Venus
08:34some of them taking advantage of the gravitational assistance of the planet
08:37during its flight
08:39The last time a space machine managed to land on Venus
08:42dates back to June 1985
08:44during the Vega 2 mission
08:46Now, we just have to wait
08:48to see what discoveries Venus LifeFinder has in store for us