The Saturn System has Water just like Earth’s … except for Phoebe

The Saturn System has Water just like Earth’s … except for Phoebe

Scientists found some variations in the D/H and 13C/12C ratios on Phoebe.

Despite the fact that none of us were here to observe the birth of our solar system, technological advancements and the desire to know more about the origin of life have enabled us to develop a model as to how all that happened. Having said that, the latest research always finds new secrets to contradict with our previous theories. Recently, researchers from the University of Arizona, the U.S. Geological Survey, the Planetary Science Institute, and the NASA Ames Research Center collaborated to discover some new properties about the Saturn system, which doesn’t fit into our current models.

The study of the abundance of certain isotopes can lead us to the history of an object. Some of the isotopes, found in our solar system, are pretty common while others were formed as a result of processes like evaporation and heating. The spectroscopic observations of the Saturn system from Cassini revealed that the water in the rings and moons of Saturn is similar to the one we have on our planet.

Given the locations of these celestial bodies, no one expected this result. What made things even more strange is the fact that the water on Phoebe doesn’t resemble the rest of the water in the system. This could potentially mean that the water present on this moon was formed farther out in the Solar Nebula.

The researching team figured out a new way to measure isotope abundances in the readings taken by the Visual and Infrared Mapping Spectrometer (VIMS) of Cassini. They studied the ratio of Deuterium to Hydrogen (D/H) in the water to determine whether it is similar to the water on Earth or not. The water made from Deuterium molecules is called ‘Heavy Water’ and its chemical formula is denoted as D2O. The word ‘heavy’ is added to its name due to the additional mass of extra neutrons.

VIMS divides all the light reflected from the Saturn system into its constituent parts to identify the elements present in it. The laboratory analysis of all the spectra with the VIMS shows that most of the water in the system, including the water on the moons (except Phoebe) and in the rings, has a D/H ratio similar to terrestrial water. This discovery is against our current model which suggests that the D/H ratio should be higher in outer parts of the solar system. Scientists involved in this research mentioned that the acceptance to this discovery would mean that we will need to change our current models. They said,

The terrestrial-like D/H of Saturn’s rings and satellites may indicate a similar water source for the inner and outer solar system, or at least a change in models where the D/H varies less from inner to outer solar system, less than a factor of two from Earth to Saturn.”

On the other hand, Phoebe displayed a different behavior than the entire Saturn system. A significant increment was observed in the D/H ratio for this moon of Saturn. In fact, the value measured on Phoebe is the highest ever measured for our solar system. It indicates that it is very much possible that it was formed much farther from the sun but was inducted into the system of the gas giant due to its gravitational pull. Roger Clark, the Lead Author of the paper who is a Researcher from the Planetary Science Institute, referred to that by saying,

The D/H ratio is the highest value yet measured in the solar system, implying an origin in the cold outer Solar System far beyond Saturn.

The only other explanation for such a high D/H is that the processes have increased their supply of Deuterium over time. However, the study explained that they couldn’t find any physical evidence for that, which leaves us with no other option but to go with the first theory. Excessive amounts of Deuterium is not the only thing which made Phoebe an oddball.

Researchers also measured the isotopic ratio for Carbon (Carbon-12 and Carbon-13) in Carbon Dioxide on Phoebe and Iapetus (the only other satellite of Saturn which has measurable quantities of the compound). They found that the ratio of 13C/12C on Iapetus was identical to Earth but the readings on Phoebe were once again different. The results showed that there was 5 times more 13C than 12C on the odd moon of Saturn. It added more strength to the idea that Phoebe was formed father out in the solar system. In these circumstances, scientists need to find out the isotopic ratios from farther worlds of our solar system in order to paint a much clearer picture. The study stressed the need for this in the following words:

D/H measurements on the icy satellites of Jupiter, Uranus, and Neptune are needed to show the larger trends in the solar system but such measurements can only be done above the Earth’s atmosphere.”

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