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13-15 years old: Ice plumes at the south pole of Enceladus

 Author: Malo Robin

Je pense que le choix le plus intéressant pour aboutir à des résultats scientifiques est le satellite Encelade.

En effet, les panaches de glace découvert au pôle sud de ce satellite de Saturne ont permis de détecter et de mettre en évidence les bases indispensables à l’apparition de la vie telle que nous la connaissons. Dès les année 1980, les scientifiques ont remarqués que ce satellite était blanc et lumineux (c’est le corps le plus lumineux du système solaire) ce qui semblait vouloir dire qu’il y avait de la glace sur Encelade, donc potentiellement de l’eau. Quelques temps plus tard la Nasa accompagné de l’ESA a fait la découverte d’eau liquide sous cette fameuse surface de glace. L’anneau  E de Saturne, alimenté essentiellement  par les éjections des geyser d’Encelade, présente des nanoparticules de silice et de silicate. On constate sur Terre que la roche et l’eau ne peuvent agir pour former ce type de particule de silice et de silicate qu’à partir d’au moins 90°C et sous de fortes pressions. Il semble donc cohérent d’imaginer des zones sur Encelade, sous la glace où ces conditions sont ou ont été réunies. Le modèle de structure interne d’Encelade qui semble s’imposer actuellement suppose un océan d’eau liquide sous la couche de glace.

D’autre part, des composés organiques simple ont aussi été détectés dans les panaches de glace du pôle sud d’Encelade. Tous ces éléments font penser la seule chose qui questionne l’humanité : Est-elle la seule vie présente dans l’Univers ?

Sur Terre, la vie telle que nous la concevons, n’est possible qu’en présence d’eau liquide. Nous observons même par endroit des formes de vie qui nécessite chaleur, pression importante, eau liquide et obscurité. Encelade semble réunir tous ces paramètres.

La découverte récente d’exoplanètes orbitant dans la zone dite « habitable » autour de l’étoile Trappist-1 suscite beaucoup de questionnements au sujet de la présence possible de vie extraterrestre. Malheureusement les distances sont telles qu’à l’échelle d’une ou quelques vies humaines nous n’aurons jamais de réponse. Encelade se trouve à une distance raisonnable de la terre, elle est le plus proche « monde » où tout est réuni pour abriter des formes de vie, même bactérienne. Je suis convaincu que c’est là, à une distance raisonnable de la terre, et non pas à des années-lumière de notre planète, que les missions futures donneront des résultats aptes à répondre à la question essentielle pour l’humanité : sommes- nous seul dans l’univers ?

13-15 years old: The lakes of Titan

 Author: Louis Vidon

Until the Cassini–Huygens mission in 2004 that allows the Saturn's Moon Titan to reveal its secrets, we didn't really focus on the second largest moon of our solar system. Among the other planets, it is the only one to have a dense atmosphere, with a liquid cycle and the presence of liquid at its surface. The analysis will therefore center on those remarkable characteristics of the object, then on the possible presence of life and finally on the questions raised by the possible discovery of life.

Firstly Titan's characteristics are very close to the Earth's ones. With surface features similar to those of our planet, including dunes, rivers, lakes and possible volcanoes with a geological activity, the moon of Saturn seems to be a little Earth. What is more, with the methane cycle with rains, winds and a seasonal weather pattern of 7.5 years, it appears as a surprising Earth-like world. Scientists believe that conditions of Titan are similar to those of the Earth a long time ago. So Titan is a natural laboratory to understand the Earth history, particularly for its atmosphere evolution.

Actually, this dense atmosphere, composed mainly of nitrogen and methane , has a complex and rich chemistry, really interesting to study as much for its composition than for the consequences it has on the whole planet. Protecting Titan, the atmosphere lets minor components fall down creating huge liquid methane lakes – the only ones in the solar system – and turning molecules into hydrocarbon with the UV. Titan hosts many chemical reactions, and scientists have proved thanks to simulations the existence of organic components and molecules that may be at the origin of life. So organic processes, leading up to the creation of new molecules would have been possible in the underground. This assertion is enlightened by the presence of an underground ocean of water. That is why I dare say it is the only planet to have such inhabitable environment in our solar system, with a possible presence of life. It may reserve a lot of surprises if further space explorations.

Considering the possible existence of life and the importance to study an Earth like world, we will now focus on the consequences of the assertion life may develop at the surface without water. If so, it would be a huge revolution in Abiogenesis. In Fact, we thought chemical reactions leading up to the creation of complex organic matter, at the origin of life, were just possible in high polarity liquids. (That is to say water like liquids which have both a partial positive charge and a negative's one). But as we might prove life have developed in methane, a low polarity liquid that would, like the relativity of Einstein, completely change the space exploration.

That is why, for its exceptional characteristics, the possible presence of life and this revolutionary thesis is to my mind Titan the following stage of space exploration in order to have further information, especially about the organic processes in the underground.

13-15 years old: The hexagon at Saturn's north pole

Authors: Beltrami Valentine, Brégeon Eva, Dornbierer Astrid

Saturn's hexagon is a persisting hexagonal cloud pattern around the north pole of Saturn, which is located at about 78°N. We have chosen target 3 because we think it is the most interesting subject like Elise Kowalski says in the video.

Target 3 is really interesting and full of mysteries and question to solve. We need answers to all these questions because understanding Saturn's hexagon can help understand the Universe. We notice also that the hexagonal cloud was persisting. Why is it persisting and what makes it persist? This strange cloud is really out of the ordinary as there is one on the North Pole but not on the South Pole. It is another really interesting question that would be nice to solve.

Moreover, Saturn's hexagon has an incredible and really interesting shape. Nowhere else on Milky Way's planets, we can see something like that. We wonder why there is this type of shape and why it is so rare. On Saturn, many storms and hurricanes can be observed. We have the same incredible events on Earth. Those events are fascinating to study. Likewise, it's important to know more about that. We are sure of one thing, on Saturn the hurricane’s eye is about fifty times larger than the average hurricane eye on Earth. Maybe, if we observe those events with a bigger scale, we would learn new things about it. We might also discover how this phenomenon happens on other planets and if it is different. Many mysterious things occur on Saturn. For instance, its vortices spin clockwise while hexagons and hurricanes spin counterclockwise. We still have many things to discover from this wonderful place.

A year on Saturn equals to 29 Earth years, thus we have not been able to observe the hexagon through a year yet. Furthermore, until 2009 we could not see the entire hexagon as in 2004 it was winter on Saturn’s North Pole. The hexagon finally revealed itself on August 2009 during Saturn North pole’s equinox spring, though we know that it has been here for decades, since the first images of the hexagon were taken by the Voyager in the early 1980s. But perhaps it has been here long before we were.

The Voyager also showed images of a large dark spot outside of the hexagon but it soon disappeared into the “long winter polar night “. The spot reappeared again in 2006 and images depict another large dark spot inside the hexagon. In late 2012, the sun has made its way through the hexagon which allowed us to have a better view of it. The inside of the hexagon is said to be darker than the outside.

It is believed that the stability of the hexagon would have something to do with the lack of solid forms on Saturn. Indeed, it is a giant ball of gas.

New images taken by Cassini’s spacecraft VIMS (visual and infrared mapping spectrometer) would be good as the last images have recently been taken in visible light with the spacecraft’s wide-angle camera in 2009.

We obviously need several years to really find out what is happening on Saturn, not only would it be ashamed not to know about the causes of those phenomena, like what is so different about the south for it, not to have a hexagon as well but it will also be a waste of money.

All those arguments and questions jostled in our mind when we thought about Target 3 thus we have chosen the one about the hexagonal cloud. We would like Cassini to explore this phenomena a bit longer and deliver all Target 3's secrets. We hope you will choose that target and we thank you for taking the time to read our essay.

 

16-18 years old: Ice plumes at the south pole of Enceladus

Author: Nikki Buggenhout

Les panaches de glace du « Géant des séismes 1»

La mission Cassini-Huygens, a permis une moisson de données scientifiques extraordinaires au sein du système Saturnien. Ce système, composé d’anneaux et d’un grand nombre satellites, intriguait les scientifiques. Avec la mission Cassini-Huygens, deux sondes furent envoyées en 1997, pour arriver en 2004. Initialement programmée pour 4 ans, elle fut prolongée jusqu’en 2017, notamment au vu des découvertes liées à la lune Encelade. Ce satellite, découvert en 1789 et observé par Voyager en 1980, avait attiré l’attention des astronomes par ses propriétés inhabituelles. Encelade semblait n’être qu’une boule de glace inerte au sein de l’anneau E de Saturne, affichant un albédo proche de 1, le plus élevé des corps célestes connus. Sa surface peuplée de cratères au nord contrastait avec une zone quasiment immaculée au sud. Ces particularités ont poussé à l’exploration plus méthodique du corps grâce à la sonde Cassini.

Les scientifiques étaient loin de s’imaginer qu’ils trouveraient l’un des corps célestes les plus prometteurs quant à la présence potentielle de vie. Sa distance au soleil de 9.5AU ne lui offre effectivement pas une température de surface suffisante, étant en moyenne de 75K. La mission Cassini n’a pas seulement permis de mieux comprendre le système Saturnien dans son ensemble, mais aussi de nous éclairer sur le fonctionnement particulier d’Encelade, qui a ouvert la voie à de nombreuses nouvelles questions. C’est la raison pour laquelle j’ai choisi la cible 1.

Grace aux photos de la sonde, les astronomes ont observé à la surface de la planète des geysers de gaz froid s’élevant à plus de 50 km d’altitude. La détermination des caractéristiques de ces panaches, provenant incontestablement d’une zone plus chaude sous la surface gelée, a montré qu’ils étaient composés en grande majorité de vapeurs d’eau, mais surtout de matières carbonées (CO2, CH4), de NH3, de petites quantités de composés organiques, et peut-être même d’azote. De plus, ces jets sont à l’origine de la formation de l’anneau E de Saturne. Entretenir un tel anneau nécessite pourtant beaucoup d’énergie. L’hypothèse principale est que cette énergie résulte de frottements entre la surface gelée d’Encelade et une zone liquide sous-jacente. Le mouvement du liquide étant causé par un phénomène de marées, qui trouve son origine dans les orbites respectives et les interactions gravitationnelles entre Dioné et Encelade. Il s’agit là d’un mécanisme très complexe et insoupçonné avant les observations de Cassini, qui montre qu’Encelade n’est pas un corps gelé et inerte mais bien un corps actif. Cependant, cette explication n’est pas suffisante pour justifier la quantité d’énergie nécessaire à la production des jets gazeux. D’où ces nouvelles interrogations: d’où Encelade tire-t- elle ce surplus d’énergie, dont la source ne peut être qu’interne ? Quels mécanismes sont-ils à l’œuvre sous cette couverture de glace à l’apparence si paisible ?

Autant de questions justifient de nouvelles missions d’exploration, et qui sait, peut-être un jour découvrir la première source de vie extra-terrestre !

1 Encelade doit son nom au Géant Εγκέλαδος dans la mythologie, dont la respiration et les mouvements étaient tenus responsables des éruptions et autres secousses telluriques.

16-18 years old: The hexagon at Saturn's north pole

Author: Louis Demiot

I am a French student participating in the Cassini Scientist for a Day Contest. I have chosen target number three, because this target is, for me, an amazing opportunity to study one of the most interesting mysteries of Saturn: its hexagon.

Actually, a lot of theories have been introduced, with success or without, but none of them were finally confirmed as the global scientist community theory. This is why I am convinced that Cassini must head towards target number 3. The Hexagon of Saturn is an incredible weather phenomenon located around the North Pole of the planet. It is a persisting hexagonal cloud pattern, whose origins and mechanisms are still not explained by consensus, despite numerous theories. The hexagon has been discovered by the Voyager Mission, from the USA, in 1981, and revisited in 2006 by the Cassini Mission. The huge cloud formation measures nearly thirty-two thousand kilometers wide, almost five times the radius of the Earth. Moreover, we know that the clouds in the hexagon move really fast, over three-hundred and twenty kilometers per hour. Target number three would allow scientists to work with new pictures, infrared images or videos. These new elements, in their hands, would become new information, new details, and an important help to build a solid theory in the purpose of an international consensus about the hexagon's formation.

Studying the hexagon of Saturn would permit to understand the origin and the formation of the hexagon, but, going further, it could award us to know when the storm began, and how long it will be active. By studying the differences with the images and videos previously acquired, and the evolution of clouds trajectories and directions, we would be able to say when the clouds started to form a hexagon, and when it will disappear. Maybe we would determine it is eternal, but in any situation, the target number three must be chosen. Another fairly important element must be dealt with, actually, a hexagon is observed at the North Pole of Saturn, but not at the South Pole. The reason of the northern hexagon's presence is not already known, but the non-presence of another one around the South Pole shall indicate us a difference of structure under the clouds, between the northern and the southern hemispheres of Saturn. For the moment, the consensus about Saturn's structure is the presence of liquid hydrogen under the gaseous hydrogen clouds. The problem, then, is to know how the formation of a hexagon at the North Pole, and only at the North Pole is possible, with normally a homogeneous liquid hydrogen surface.

By studying new elements coming from Saturn's hexagon, such as new pictures, new infrared images, new videos, scientists would have new possibilities, new chances, to understand the hexagon of Saturn, its origins, its duration, its hypothetical end, or hypothetical eternity, and maybe so much more from a firsthand perspective. That is why target number three is the target I choose, with conviction and confidence.

Last Update: 1 September 2019
24-Feb-2020 21:31 UT

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