Iren Su Dulger

Year: 2015-2016

School: Istek Ac badem Anatolia High School

City: Kad köy - Istanbul

Target: Rhea and Tethys

"Rhea and Tethys are as interesting as the Greek mythology sisters they got their names from and I'm sure that they fascinate many scientists as they amaze me with their uniqueness. Tethys has the lowest density of all major moons in the Solar System and is made of mostly water ice and a small amount of rock and unidentified dark material. Rhea is one of the most heavily cratered satellites and a faint oxygen atmosphere exists around it which makes Target 3 more preferential for me.

In this mysterious universe I think to look further we should first discover our near surroundings. It only makes sense if we understand our close range before we move onto depths of space yet we don't even have enough information about tiger scratches in Tethys. We don't know the real reason behind these scratches or why they haven't occurred until now. There is a variety of questions raised by these scratches. Are they really formed by chemical impurities? Or are they a result of gas jests coming beneath the surface? Will they be erased by the exposure to space environment? I strongly believe these questions are of great importance so they shouldn't be overlooked. If we can figure out the reason behind these scratches we can understand the chemical properties of Tethys better.

It is suggested by models that Rhea could be capable of sustaining an internal liquid-water ocean through heating by radioactive decay, with this target we can find a chance to prove this scientifically, and end debates about whether it has a rocky core or it is same throughout. Furthermore Tethys has Pac-Man heat map due to bombardment by the energetic particles. This is the second planet found by Cassini that has this property. Also the occultation of Rhea and Tethys are believed to give opportunity to assess the orbits which can change and the results of these assessments can help us understand the change of the orbits and the factors of change.

Over 2000 exoplanets have been discovered and a few are candidate planets, we know that terrestrial planets are more likely to be in the habitable zone thus we have enough knowledge to investigate other planets. We could study any exoplanet we want. In addition there were already flybys dedicated to Enceladus. However none of the flybys of Cassini got close to Tethys and Rhea as they did to Enceladus. Even though there are contradictions whether Tethys' tiger scratches will disappear or not, there is a chance that they may be erased and their disappearance would prevent us from observing them. This means that we may have limited time to examine them and this is an investigation that shouldn't be risked. In this captivating universe any discovery is mind blowing but because of all these reasons it is time we point Cassini's camera to Tethys and Rhea."

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