Saturn’s rings have their own atmosphere

[C1ay]

Data from the NASA/ESA/ASI Cassini spacecraft indicate that Saturn's majestic ring system has its own atmosphere - separate from that of the planet itself.

 

lefthttp://hypography.com/gallery/files/9/9/8/spectrum_thumb.jpg[/img]During its close fly-bys of the ring system, instruments on Cassini have been able to determine that the environment around the rings is like an atmosphere, composed principally of molecular oxygen.

 

This atmosphere is very similar to that of Jupiter's moons Europa and Ganymede.

 

The finding was made by two instruments on Cassini, both of which have European involvement: the Ion and Neutral Mass Spectrometer (INMS) has co-investigators from USA and Germany, and the Cassini Plasma Spectrometer (CAPS) instrument has co-investigators from US, Finland, Hungary, France, Norway and UK.

 

Saturn's rings consist largely of water ice mixed with smaller amounts of dust and rocky matter. They are extraordinarily thin: though they are 250 000 kilometres or more in diameter they are no more than 1.5 kilometres thick.

 

Despite their impressive appearance, there is very little material in the rings - if the rings were compressed into a single body it would be no more than 100 kilometres across.

 

The origin of the rings is unknown. Scientists once thought that the rings were formed at the same time as the planets, coalescing out of swirling clouds of interstellar gas 4000 million years ago. However, the rings now appear to be young, perhaps only hundreds of millions of years old.

 

Another theory suggests that a comet flew too close to Saturn and was broken up by tidal forces. Possibly one of Saturn's moons was struck by an asteroid smashing it to pieces that now form the rings.

 

Though Saturn may have had rings since it formed, the ring system is not stable and must be regenerated by ongoing processes, probably the break-up of larger satellites.

 

Water molecules are first driven off the ring particles by solar ultraviolet light. They are then split into hydrogen, and molecular and atomic oxygen, by photodissocation. The hydrogen gas is lost to space, the atomic oxygen and any remaining water are frozen back into the ring material due to the low temperatures, and this leaves behind a concentration of oxygen molecules.

 

Dr Andrew Coates, co-investigator for CAPS, from the Mullard Space Science Laboratory (MSSL) at University College London, said: "As water comes off the rings, it is split by sunlight; the resulting hydrogen and atomic oxygen are then lost, leaving molecular oxygen.

 

"INMS and CAPS see molecular oxygen ions, and CAPS sees an ‘electron view’ of the rings. These represent the ionised products of that oxygen and some additional electrons driven off the rings by sunlight."

 

Dr Coates said the ring atmosphere was probably kept in check by gravitational forces and a balance between loss of material from the ring system and a re-supply of material from the ring particles.

 

Last month, Cassini-Huygens mission scientists celebrated the spacecraft's first year in orbit around Saturn. Cassini performed its Saturn Orbit Insertion (SOI) on 1 July 2004 after its six-year journey to the ringed planet, travelling over three thousand million kilometres.

 

Source: ESA

[Tormod]

Great story, C1ay.

 

For an article I'm doing at work I called up one of the scientists, Knut Svenes, here in Norway who works on the Cassini data and wow they are learning a lot about the Saturnian system. The atmosphere thing is something they have expected but only now been able to prove.

 

I had to ask him the inevitable, of course, whether there was any chance for life but he flatly denied it. We are looking at a very thin atmosphere in a very harsh environment and little heat...but the idea is neat.

[Turtle]

I had to ask him the inevitable, of course, whether there was any chance for life but he flatly denied it. We are looking at a very thin atmosphere in a very harsh environment and little heat...but the idea is neat.

 

___More & more we see that a harsh environment is no guarantee of a lack of life; not only is the idea neat, it is increasingly possible. As Cassini continues its mission, further study of the rings may reveal seasonal changes with widely varying temperature ranges not obvious from a short data set.

___I don't see where the article comments on hoe thick the atmosphere is, i.e. how far does it extend from either side of the 150KM ring plane? Is it equally thick from one side to another? Just thinking out loud; good article C1ay. :eek_big:

[EWright]

Isn't one theory of how life began on earth, that it was seeded by debris from other parts of the galaxy slamming into the earth in the past? Why then wouldn't such theorists presume the same seeds were scattered throughout other parts of the solar system? Given the persistance of life forms (especially microbial ones) to survive or adapt to harsh conditions, would supporters of this theory not expect that they might exists in any area with an atomoshpere and water of any sort?

 

I'm not sure how much support there is for this particular theory. It is something I thought I heard in the past, and which came to mind given this discussion. Also, isn't one of Jupiter's moons (Europa?) suspected of having liquid (water?) oceans undera crust of thick ice? What are the discussions of the possibilities of life here?

[Tormod]

Isn't one theory of how life began on earth, that it was seeded by debris from other parts of the galaxy slamming into the earth in the past? Why then wouldn't such theorists presume the same seeds were scattered throughout other parts of the solar system?

 

That is what the theories say - the same elements were scattered all over the solar system, and are still here in pristine form inside comets. This is one of the prevalent ideas, and was supported by the initial findings in the Deep Impact mission this summer.

 

The observations at Saturn also appear to support such a theory.

 

However, the rings themselves are much too young to have been part of the early spreading of the chemicals which form the building blocks of life (as we call them), they are merely a few hundred million years old, compared to the 4,6 billion years that is the age of Saturn and the rest of the Solar System.

 

If the rings are a result of comets being crushed by Saturn, and then the debris being scattered around and "harvested" by the moons (several of Saturn's moons orbit inside the ring's gaps), then they were formed by the same kind of matter that spread those initial chemicals to Earth and as you mention, Europa.

 

However, water is not a sign of life. It is not a byproduct of it. It is, however, an expected prerequisite for it (we only know water-based life). All biological processes as we know them leave an imprint due to metabolism. This is observed on Earth. That is why methane on Mars and Titan have been interpreted as possible signs of earlier (or even current) life.

 

So yes, water on Europa, especially since it is expected to be a sub-surface ocean (the thickness of the crust is still a matter of debate since it is hard to measure - this will hopefully be done with later Jupiter probes), which means it may be a warm ocean if there are deep-sea vents, for example. That makes it possibly a very likely place for life to arise But we have yet no signs of it, and no tests for it.

[Jim Colyer]

It is amazing how we can determine Saturn's rings have an atmosphere all their own. I am sitting in the science library at Vanderbilt University in Nashville. I still get a kick out of astronomy after all these years.

 

Jim Colyer Astronomy http://jimcolyer.com/papers/entry?id=2