SCIENTIST FOR A DAY

RHEA

PAN

ENCELADUS

Entry # 197 - Rhea

The target, that will yield the most scientific data, is Rhea. I believe Rhea had ice plumes like Enceladus does today. It had a layer of liquid below the surface that spewed out producing a ring. For some reason it stopped.  There are facts to support this hypothesis.

These two satellites share similar physical characteristics. Both have surface temperatures about -200° Celsius. Therefore, Rhea had an appropriate temperature for the phenomenon to occur. Rhea, and Enceladus are composed of 2/3 ice with a homogenous core. The density of the two satellites is similar, 1.33g/cm ³for Rhea, and 1.24g/cm³ for Enceladus. Both have similar misshapen surfaces.  On Rhea, craters seem to be contorted. That had to be caused by some sort of tectonic process. A layer of liquid water under the surface could have caused this distortion. A photograph could show if this distortion is continuing. If the distortion is still occurring, and there are no ice plumes, it would prove something else was distorting the craters besides a liquid ocean. However, if the distortion has stopped it would prove that the distortion had something to do with the former subterranean liquid ocean. Another characteristic of Enceladus is the “tiger stripes” on the southern pole. Looking at color-filtered photos of Rhea, you can see similar shapes that are possibly “tiger stripes”. More photos could determine this. Rhea has dense cratering on its leading half while on the trailing half cratering is much less dense, a sign of a younger surface. This resurfacing could have taken place because the now dormant ice plumes emitted material which dropped back to the surface filling craters. This process would change the surface and make it appear younger. A photo could also show evidence of ancient ice plumes on Rhea. If a photo showed evidence of  dormant ice plumes we could get an idea of what Enceladus will look like in the future. This would help us understand the processes occurring on Enceladus, and would give us a better understanding of what is taking place. On Rhea and her sister Dione wispy lines can be seen. As other scientists have said, these lines could be a result of ice plumes. If that is the case, Rhea could give us a better idea of what Enceladus will evolve into once its ice plumes become dormant. A photograph of Rhea would not just give us clues about what forces are at work upon it, but also what forces have worked on other satellites.

Evidence Rhea once had a liquid ocean feeding ice plumes that ejected material into space convince me that Rhea would yield the most scientific data. Rhea has many possibilities. There still may be active ice plumes on Rhea. We may catch a ring being created! Maybe we will find remnants of an ancient ring. I believe that an image of Rhea could unveil new features or reveal ancient, and provide us with a better understanding of Saturn’s icy satellites.

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Entry #203 Enceladus

  It has been proven on Earth that there can be many types of bacteria that live in harsher environments than any human could have imagined. This was shown in Lechuguilla cave in New Mexico where traces of bacteria were found living in acid. This bacterium was so small that at first it was thought not to be real. Tests showed that it was in fact a bacterium that created the sulfuric acid left there some 250 million years ago by petroleum deposits. If bacteria can live in such a harsh environment, then why not environments like the one on Enceladus?

           Since the last Cassini fly-by of Enceladus, “tiger stripes,” a geyser mark that has the look of a tiger’s markings, has gotten scientists to make the assumption that there may be a liquid ocean beneath the surface of Enceladus. To contain life, you need liquid and some sort of an organic material. The tiger stripes contain some gasses including carbon dioxide. There could be organic material to originate a bacterium and organic materials to survive. Enceladus is like Earth in a few ways. It actually may have pure water volcanic activity, or ice being melted by lava beneath the surface. Enceladus has an atmosphere and, though it is thin, it means that gasses are either originating from the surface or somewhere beneath the surface. Since Enceladus is such a small satellite, it needs a large amount of  new material to keep an atmosphere. That leads to the theory that constant eruptions occur on Enceladus. Another reason that this could contribute to life on Enceladus is because it would limit the variation in temperature which would make keeping a life form around much easier. Also, the temperature was measured 20 degrees Celsius higher on the South Pole of Enceladus. This is where the tiger stripes are, and where the ice particles that are feeding Saturn’s E ring are located. This warmth could very well be what could help a life form survive on Enceladus. 

           These reasons explain why I think there may be some sort of a bacterium Enceladus. It has a primitive atmosphere.  There could be complex organics that could support life.  Bacteria exist in exotic places on Earth similar to the environment on Enceladus. If I am chosen, my photograph would be of the South Pole of Enceladus. I will look for new signs of a bacterium such as more tiger stripes, or changes in the stripes, other signs of volcanic material, and new organic material. I think that the most important discovery that could be found in the image is evidence of some change from previous images that might suggest a biosignature.

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Entry # 237 Pan

I think taking a picture of Pan would help us better understand Saturn’s rings, the origin of the Encke Gap, and the evolution of the satellite itself.  Because of Pan’s location, we suspect that it is responsible for the Encke Gap. Pan is a shepherd satellite. That means it acts like a “snow plow” in the ring pushing the particles out of its way. Where do those particles go? Maybe some are attracted to Pan.   Is Pan physically changing by being a shepherd satellite? Maybe Pan is getting larger by attracting particles while maintaining the Gap. Somehow this tiny 17 mile satellite keeps the large 200 mile wide Encke Gap clear.  One clue is that Pan has a ringlet of particles occupying nearly the same orbit.  Why is that? Could the ringlet be particles that are trailing off of Pan like the tail of a comet? Is the ringlet always there? Pan may go over the ringlet and collect the particles.  The waves in the rings that are supposedly caused by this small satellite may be a reaction to particles from the rings being pulled in by Pan’s gravitational attraction. By taking this picture we may find some evidence answering these questions.  The route to discovering what happened to particles in the gaps, and if shepherd satellites evolve or stay the same, will begin.
                        If we target Pan, and then compare the photograph to previous images, we may be able to observe changes to the surface, overall shape, or size of the satellite.  It may indicate that Pan attracted particles and became larger. If this satellite is getting larger, then it would explain what happens to the particles in the gap in Saturn’s rings. If we learn more about Pan, and how its orbit alters the rings as it passes through them,  we might be able to discover more satellites in the gaps by finding places in Saturn’s rings that display similar characteristics to Pan’s presence.

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