Winners - United Kingdom
10 - 12 years old - Saturn's rings, with three of Saturn's moons: Tethys, Enceladus, and Mimas
I think that it will benefit scientists the most if the space probes went to Saturn’s rings and its three moons for the following reasons:
Jupiter, Uranus and Neptune all have rings however they are very faint; they don’t compare to Saturn’s beautiful, colossal rings. The rings are approximately 270,000km in diameter but are relatively thin being a maximum of 1km wide, which, according to NASA makes it difficult for the rings to be viewed edge on from Earth, therefore the Cassini space probes will be able to take very detailed pictures of Saturn’s rings. Each ring is composed of many ringlets of ice particles which vary from dust-sized to 3m diameter. Furthermore, In 1997 Cassini space probes visited Saturn and the pictures taken were able to help scientists predict how old Saturn’s rings could possibly be due to the amount of dust content shown in the rings as a series of red and blues. Therefore, further pictures from the space probes can help scientists to research further in order to help them come to a reasonable prediction to how old Saturn’s rings actually are.
Enceladus- Enceladus is one of the brightest objects in our solar system and reflects almost one hundred percent of the sunlight making that ht it. Because this moon reflects so much sunlight its surface temperature is extremely cold; on average -201 degrees Celsius. Being as wide as Arizona, it is quite similar to Mimas however it is smoother and a lot brighter. But one of Cassini’s future goals is to investigate the composition and distribution of surface materials on Enceladus and also determine its characteristics and geological history. Therefore, if the space probe was to look at Enceladus and take detailed pictures of its surface scientists could do further research to predict the composition and distribution of the surface materials Enceladus consists of.
Mimas- The surface area of Mimas is made up of many craters which- if this target is chosen- would be extremely interesting to look at in detail if the space probe was to take a photo of target one. Mimas’ low density indicates that it is made up of mostly water ice and a small amount of rock. Mimas seems to be frozen at a temperature of 209 degrees Celsius. Scientists find this puzzling because Mimas is closer to Saturn than Enceladus but the mimantean orbit is much more out of round compared to Enceladus’. Therefore, Mimas should have much more tidal heating. Yet, Enceladus has water geysers and Mimas has one of the most heavily crated surfaces. This leads scientists to thinking that Mimas has been around for an extremely long time. So, if target one was chosen scientists could analyse the evidence they have from the pictures to make predictions to why Mimas is the way it is.
Overall, I would say the next Cassini mission in 2017 should be to take an image of Saturn’s rings and its three moons because I think it’ll be most beneficial for scientists.
10 - 12 years old - Movie of Saturn's moon, Tethys, passing behind Rhea
I believe that the best of the three options would be a short movie of Saturn’s moon, Tethys, passing behind Rhea. Here is why I chose this option:
If Cassini makes a short movie of Tethys then we will be able to see in detail Saturn’s moon passing behind Rhea. This will benefit us because we will be able to see what things are like on different planets. A distant image of Jupiter would be unnecessary because we already have some of those and if it’s distant then we won’t be able to see much detail.
Furthermore, Cassini can capture the structure and features of both Tethys and Rhea; such as whether there are any craters or an atmosphere.
The film will show the exact movements of the two moons. Pictures don’t show as much detail. For example, a picture may be taken of Tethys passing behind Rhea. It will only show what this and the moons look like in one position; it could look completely different when in another position.
Another way that this will benefit us is that the set of grouped-together images will show something very special called an ‘occultation.’
Occultations happen when one object, like a planet or a moon, passes in front of another, hiding it from view. In this case, Rhea will pass in front of Tethys. Occultations like this give us a very accurate way to assess the orbits of these moons, which change slowly over time.
In addition, Rhea and Tethys are still a mystery to us. Scientists are still unsure of what the interior of Tethys looks like. Some measurements suggest it has a rocky core, whereas other data indicates that it is the same throughout. Tethys is just as intriguing. It is composed of water-ice, making it one of the whitest and brightest objects in the Solar System.
Also, some reddish streaks, named “tiger scratches” have been sighted; they don’t match with any surface features. Their origin is currently unknown, which is why the third option will be of aid to our space knowledge.
Rhea was initially discovered by Giovanni Domenico Cassini. He was born on June 8th 1625 in Perinaldo, Italy and discovered Rhea in 1672. Tethys was found by the same man in 1684. Cassini named the four moons he discovered, the Sidera Lodoicea. The English translation of this is the Stars of Louis, after King Louis IV. Rhea was referred to numerically as Saturn V based on its distance from the planet. Tethys’ numerical reference was Saturn III.
To conclude, I hope my research has been of use to the investigation. I feel that the best option is definitely the third one and I am sure many others will agree with this decision.
13 - 15 years old - Saturn's rings, with three of Saturn's moons: Tethys, Enceladus, and Mimas
I believe that some of the most unique and fascinating moons in the solar system must be captured by the Cassini Spacecraft. Not only can this provide an insight into the age, composition and distinctive features of each of these bodies, but it can help us to unravel some of the greatest astronomical mysteries posed by previous missions and flybys. By photographing and analyzing these awe-inspiring natural satellites, we can also make some fantastic breakthroughs about the formation and mechanism of Saturn's inexplicable yet stunning rings.
Tethys, discovered in 1684 by G. Cassini, is mainly comprised of water ice and partially by rock. A previous Cassini flyby obtained a near-infrared spectra which confirmed this. However it also mapped an unidentified dark material, and earlier this year, some unfathomable red streaks across its surface. Scientists are still baffled today, and I think it is essential that we conduct further research to try and understand why this material exists on Tethys and how it got there. This leads onto the still unknown formation of this moon. Two of the most convincing theories are the subnebula, or an accretion disc - proposing the puzzling possibility that Tethys was formed out of a star. In 1980, Voyager 1 discovered the Ithaca Chasma, a valley approximately 3 km in depth. It Is believed that the freezing of internal water caused the moon to expand, or due to tidal heating caused by orbital resonance between Dione and Tethys. The Odysseus Crater was later discovered in 1981. It is a gargantuan impact crater 450 km in diameter, 40% of Tethys' diameter. It truly is a miracle of physics; a devastating impact that caused the crater should have demolished the moon itself.
Mimas is similar in composition to Tethys and it is mostly covered with craters, chasmata and cartenae. The most distinctive geological feature is known as Herschel, also an impact crater that in theory, should have shattered the planet. It seems that these moons have some incredible forces of resistance that are yet to be discovered. What is most intriguing about Mimas is how it caused displacement of material between Saturn's A-Ring and B-Ring, known as the Cassini Division; once again, orbital resonance is the culprit. Further exploration could tell us so much more about Saturn's ring system and formations like the Huygens Gap.
Enceladus, is Saturn's sixth largest moon and is covered in water ice. Despite its small size, it is one of the largest contributors to Saturn's ring system. Various fly-bys discovered powerful cryovolcanic plumes that project water vapour, ice particles, sodium chloride crystals and other solid material into space. These geyser like projections, similar in composition to comets, fuel Saturn's widest ring, the E-Ring, and I think another Cassini mission will give us information about the significance of Enceladus to Saturn's ring system and its stunning geological activity.
13 - 15 years old - Distant image of Jupiter
When it comes to deciding which space object we should explore next, it's always a tough choice. There is still so much we don’t know, so many mysteries just waiting to be uncovered. However, out of all the three targets, the one that particularly captured my interest was target two. A distant image of Jupiter, which might just open a door into a new phase of space exploration.
Jupiter is a gas giant, and, with a diameter of 139,822 km, is currently the largest planet in our Solar system. The Hubble space telescope has taken many photographs of the planet close-up, allowing scientists to further research its surface, atmosphere and the “Great Red Spot” storm, and make amazing progress. So, having the ability to get such detailed photographs from just about any angle, many might wonder why we’d need to bother with a distant image. Read on!
Exoplanets are planets beyond the Solar system, orbiting a different star. Scientists believe that over 100 billion stars with such planets exist within the Milky Way. With the help of NASAs Kepler telescope, thousands have been discovered in the past two decades, and the majority of these planets turned out to be gas giants – just like Neptune and Jupiter. But many more still go unnoticed, simply because they’re too far away, do not emit their own light and the stars around which they are orbiting are too bright for us to see them. If the Cassini spacecraft takes images of Jupiter from Saturn – an impressive 645 million kilometres between them – scientists can get a good idea of what exoplanets that have an atmosphere look like from distances even greater than this. Jupiter has already been observed from a long way away by Voyager 1 in 1979, but, although the images proved to be very valuable, Cassini can take much more reliable ones. The technology that this spacecraft has on board is more developed, and will allow scientists to take measurements with greater accuracy.
Finding and studying exoplanets is vital if we want to expand our knowledge on the formation of the universe. Astrophysicists have already begun to question theories about the formation of our own solar system, because Hot Jupiter exoplanets directly oppose the established nebular theory. It states that outer planets are mostly gaseous because hydrogen compounds condense at lower temperatures (further away from the Sun). According to this theory, Hot Jupiters (gas giants) should not exist, because they orbit their home star even closer in than Mercury!
Discovering exoplanets is also very important to the next generations. Not only is the prospect of finding life somewhere other than Earth very intriguing, exoplanets that are able to sustain it – called Exo Earths – could be a possible evacuation point should something happen to prevent us from living on Earth any longer. Although no Exo Earths have yet been discovered, observing Jupiter from a distance could prove very useful to scientists searching for them.
13 - 15 years old - Movie of Saturn's moon, Tethys, passing behind Rhea
I believe that of the three candidates, an attempt to study Saturn’s enigmatic moons by the means of a video is most appropriate, because of the three, the least is known about Rhea and Tethys.
Tethys has an extremely high proportion of water and ice in its composition, which remains to this day not fully or satisfactorily explained, and in general very little is known about how it evolved to its present state. Analysis of its other constituents has also not been unambiguously conclusive. Images taken by Cassini in April 2015 showed red streaks that couldn’t be seen from previous images because of insufficient lighting, showing that we have barely scratched the surface of Tethys’ mysteries. A colossal crater named Odysseus was photographed in great detail when Cassini flew by in 2015. Cassini took the photograph using light outside of the visible spectrum, which explains how it detected what none of its predecessors did. The impact crater is much lighter and more clearly visible than the rest of the moon, possibly due to a different composition of minerals which may have been exposed when the crater was formed, or deposited by the body that created the impact crater. The image was created using a combination of ultraviolet, green and infrared light photos all superimposed on each other. It can be seen that the diameter of the crater is two-fifths of the diameter of the moon itself, so the collision was a major event in the geological history of Tethys which may have thoroughly changed its future.
Even less is known about Rhea, making it a huge mystery. It was originally assumed that Rhea had a rocky-core, but calculations based on the moon’s moment of inertia indicated that it is homogenous, i.e. has an icy core. Some papers have implied that Rhea is partially differentiated. Certain models suggest that Rhea could maintain an internal liquid-water ocean by heating from radioactive decay of heavier elements. On 6 March, 2008, NASA announced the possibility of Rhea having its own ring system, which would be significant because it would then be the first moon to have one. It was inferred from changes in the flow of electrons trapped by Saturn’s magnetic field, and the findings of small ultraviolet bright spots distributed along Rhea’s equator. However, when Cassini flew by, it found no traces of dust or debris that could be potential ring material, so another explanation is necessary to explain earlier observations.
Both moons have chances of harbouring liquid water, and as a consequence, life. It should prove fruitful to the scientific community to conduct a study and better understand these moons. For example, they could be used as examples for how life might begin, or what conditions inhibit the thriving of life. For the above stated reasons, I believe that we should make this short movie.
16 - 18 years old - Saturn's rings, with three of Saturn's moons: Tethys, Enceladus, and Mimas
I believe that the target that would yield the most information is target number one: an image of Saturn’s rings, with three of Saturn’s moons (Tethys, Enceladus and Mimas). The main reason I think that this target is both the most interesting and one with most potential is that there are aspects of both the rings and the moons that we know very little about, and one image of them all would be an efficient way to (possibly) gain more knowledge in order to amend this.
One example of the mysterious aspects of this target is the unidentified dark material on the surface of Tethys. At an age with such incredible technology available to us, a lot of materials close enough to be viewed from Earth can be identified by one method or another. The fact that this material cannot be identified from Earth is fascinating, and undoubtedly worth researching.
Unidentified material has been found on the surface of Saturn’s moons before, and then, over time, followed to be identified. If identifying this new, dark material would be as conclusive as the last time the same occurred, the mission could be considered nothing other than successful, as previously it helped scientists gain knowledge regarding the primordial material that majorly aids their (and our) understanding of the formation of our planet.
Though this is the part of the target that I find most interesting, there are also many things we could learn regarding the other moons and the rings. Mimas and Tethys both have rocky, heavily impacted surfaces. They are covered in craters, which, if studied, could help us learn both about the moons, the materials that form them, and the causes of the craters. There is an especially interesting crater on Tethys: the Odysseus, which is 400km in diameter. This is one of the larger craters in the solar system, and is even more fascinating when bearing in mind the relatively small size of Tethys- it covers nearly two fifths of the moon’s total surface.
These two moons provide a stark contrast to Enceladus’ surface, which is icy and gleaming white, showing a mixture of smooth plains, impact craters, and most distinctively, tiger stripes. These were first observed by a Cassini mission in 2005, and enabled further discoveries surrounding the geysers of the moon.
Saturn’s rings are also very promising. They are the most extensive planetary ring system of any planet in our solar system, and there is still a lot to be learnt about them. Their origin, for instance, is unconfirmed. A picture of them would enable scientists to find more out about the materials forming it, and therefore the history of the rings.
Additionally, there have already been missions which have photographed all of the components of this target- all of which have been incredibly conclusive. However, there is still much more information to be discovered surrounding this target, which is why I believe that it is the best one.
16 - 18 years old - Movie of Saturn's moon, Tethys, passing behind Rhea
All three targets have a very high scientific potential; however, having to select only one of them, my choice is target #3, which consists of 27 images taken 60 seconds apart to create a sequence of the transit of Tethys behind the disk of Rhea.
There are several reasons that have led me to choose this target. Recently, Cassini spotted a series of interesting, arc-shaped, reddish streaks cutting across the northern hemisphere of Tethys. These streaks do not seem to be associated with any known geological feature and have just come into view, thanks to new, favourable lightning conditions in Rhea’s northern hemisphere. In fact, these streaks were discovered so recently that few observations of them have been collected so far: any new information would be very valuable to shed light on their origin. Current theories include chemical impurities within the surface ice, exposure of internal material, outgassing.
Another compelling scientific objective that imaging target #3 would address is Rhea’s ring system. The existence of this system was first suggested by the symmetrical, gradual nature of the pattern of magnetospheric depletion (regarding in particular energetic electrons). Whereas other moons show sudden, steep cut-offs, Rhea exhibits a much more gentle, symmetrical pattern that can be explained by rings. Over the years, further evidence has grown in favour of the existence of a tenuous ring system around Rhea, including the presence of a series of spots around the moon’s equator which, being very bright in the UVs, could have been created by the deorbit of portions of the ring material. Rings can deorbit because of gravitational instabilities, for example (see the Martian moon Phobos, which will soon be torn apart by tidal forces and form an unstable ring of debris). So far, no other moon is known or suspected to possess a ring system.
To date, Cassini’s cameras have been unable of directly observing the potential ring system, casting some doubts on its existence. However, the observation of target #3 might allow us to settle the case once for all. Tethys, in fact, has an extremely high albedo – it is the second brightest object in the solar system, not considering the Sun. Therefore, if a ring system were actually present around Rhea, it would probably reveal itself by causing the brightness of Tethys to gently decrease before the first contact (the moment when Rhea’s disk starts transiting in front of Tethys) and then symmetrically increase just after the last contact.
Finally, obtaining sequences of transits such as this one can be useful to pinpoint the precise locations of the two moons, thus reducing uncertainties in their orbital parameters and monitoring possible changes in their motion. Because the Saturnian system is a “scale model” of the solar system, knowing its dynamics very precisely is a top priority to build better simulations of the formation and evolution of the entire solar system.