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Dead Cassini spacecraft could solve mystery of Saturn's hot atmosphere

Data from NASA's Cassini spacecraft is still helping scientists to explore Saturn, years after the spacecraft "died."
Data from NASA's Cassini spacecraft is still helping scientists to explore Saturn, years after the spacecraft "died."
(Image: © NASA/JPL/ASI/University of Arizona/University of Leicester)

A spacecraft that died in 2017 is still providing insights about Saturn, the planet it studied up close for 13 years.

NASA's Cassini spacecraft helped scientists to discover why Saturn's upper atmosphere is so hot, which puzzled planetary scientists for decades since the planet is too far from the sun to receive our star's heat. But, using old data from Cassini, scientists are closer to solving this mystery.

This new work, which was conducted by NASA and the European Space Agency and led by Zarah Brown, a graduate student at the University of Arizona's Lunar and Planetary Laboratory, suggests that it's auroras that are heating up Saturn's atmosphere. These auroras are triggered by the constant stream of charged particles from the solar wind, which interacts with charged particles that flow from Saturn's moons and creates electric currents.

Related: Amazing Saturn Photos from NASA's Cassini Orbiter

This insight not only helps scientists understand what is going on at Saturn, but perhaps also at gas giant planets in general. Jupiter, Neptune and Uranus all have strangely hot upper atmospheres as well. There are also numerous exoplanet gas giants far outside of our solar system that may exhibit similar behavior.

"The results are vital to our general understanding of planetary upper atmospheres, and are an important part of Cassini's legacy," study co-author Tommi Koskinen, a member of Cassini's Ultraviolet Imaging Spectrograph instrument team, said in a statement from NASA's Jet Propulsion Laboratory

Researchers previously used Cassini data to build a map of the temperature and density of Saturn's upper atmosphere, which was not well known before the spacecraft arrived at the planet in 2004. In this study, this map helped scientists to study how electric currents from Saturn's auroras heats the planet's upper atmosphere, generating the solar wind. The solar wind, in turn, distributes energy from the poles (where the auroras are located) towards the equator. That energy then heats the equator to twice the temperatures than could be generated from the sun's heat.

It's common for archival data from spacecraft like Cassini to continue providing new insights long after the craft are no longer operational. This particular dataset came from Cassini's final few months at Saturn when it did 22 very close orbits of the gas giant before deliberately hurling itself into the planet on Sept. 15, 2017 (to prevent possible Earthly contamination of Saturn's icy moons, which could host microbial life.) 

For six weeks, Cassini examined bright stars in the constellations Orion and Canis Major, watching as the stars rose and set behind Saturn. By observing the shifting starlight, scientists were able to learn more about the density of Saturn's atmosphere. Since density decreases with altitude, the rate of decrease is dependent on temperature, allowing scientists to estimate temperatures in Saturn's upper atmosphere. 

Cassini's observations showed the temperatures peaking around the auroras, in turn providing evidence that it is electric currents are what  Saturn's upper atmosphere so hot. Wind speeds on Saturn were also determined using density and temperature measurements.

A paper based on the research was published Monday (April 6) in Nature Astronomy

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  • sunstance
    My advice is that Saturn's Cassini atmosphere probe will never happen again in fact I doubt that any one will be going to Saturn , leaving anything on Saturn . and any future development will not go to Saturn . what I want you to think about is this, every time we send something to another planet we send tiny little viruses to other worlds. and if ever there was life and it worked out we sent this probe to another world as an example I can only imagine what would happen to a lesser creature. so I would say never again will a probe be sent into any atmosphere based on the act is considered dangerous . the next development right now being made to go to Saturn as far as I ma concerned is cancelled and anyone endangering earth will be treated as earths enemy.
    Reply
  • SpaceNerd-ish
    sunstance said:
    My advice is that Saturn's Cassini atmosphere probe will never happen again in fact I doubt that any one will be going to Saturn , leaving anything on Saturn . and any future development will not go to Saturn . what I want you to think about is this, every time we send something to another planet we send tiny little viruses to other worlds. and if ever there was life and it worked out we sent this probe to another world as an example I can only imagine what would happen to a lesser creature. so I would say never again will a probe be sent into any atmosphere based on the act is considered dangerous . the next development right now being made to go to Saturn as far as I ma concerned is cancelled and anyone endangering earth will be treated as earths enemy.


    Hmmm, I think we will send spacecraft to other atmospheres. Due to our increasing demand for resources, what is to stop us from finding them? Keep in mind probes/robots can be sterilized too. So, I think we will send numerous probes/spacecraft to other planets.
    Reply
  • sunstance
    Ok so what I am saying is that we need to rethink everything about what we think we are doing.
    If another lifeform could exist them it will be treated as another (does) exist.
    and that environment must be protected and respected.
    We have enough knowledge to know what can happen with contaminates in one form or another.
    It would be prudent to start to build a 100 metre or 200m metre telescope for space .
    As it is responsible and reasonable with any future space plans to be able to see what is going on other worlds.
    that will include all future plans even ones that are up to an including almost ready to go will be cancelled until further notice. Sending anything form now on will be considered an act crime against humanity until humanity gives the OK . anyone sending anything any where will now have to ask and if this does not happen god help us for what we have done! any questions.
    Reply
  • SpaceNerd-ish
    sunstance said:
    Ok so what I am saying is that we need to rethink everything about what we think we are doing.
    If another lifeform could exist them it will be treated as another (does) exist.
    and that environment must be protected and respected.
    We have enough knowledge to know what can happen with contaminates in one form or another.
    It would be prudent to start to build a 100 metre or 200m metre telescope for space .
    As it is responsible and reasonable with any future space plans to be able to see what is going on other worlds.
    that will include all future plans even ones that are up to an including almost ready to go will be cancelled until further notice. Sending anything form now on will be considered an act crime against humanity until humanity gives the OK . anyone sending anything any where will now have to ask and if this does not happen god help us for what we have done! any questions.



    Thank you for clarifying! I was a bit asleep when I read your reply. I only have one question: since humans can have bad reactions to alien life, don't you think it'd be safe if we kept quiet about them? I really enjoy thinking about the possibility of meeting extraterrestrial life, but there may be other people who'll ruin the experience. And that would be horrible for the people who just want to seem them.
    Reply
  • SpaceNerd-ish
    sunstance said:
    Ok so what I am saying is that we need to rethink everything about what we think we are doing.
    If another lifeform could exist them it will be treated as another (does) exist.
    and that environment must be protected and respected.
    We have enough knowledge to know what can happen with contaminates in one form or another.
    It would be prudent to start to build a 100 metre or 200m metre telescope for space .
    As it is responsible and reasonable with any future space plans to be able to see what is going on other worlds.
    that will include all future plans even ones that are up to an including almost ready to go will be cancelled until further notice. Sending anything form now on will be considered an act crime against humanity until humanity gives the OK . anyone sending anything any where will now have to ask and if this does not happen god help us for what we have done! any questions.


    I actually have another question: is that the James Webb Telescope in your profile picture?
    Reply
  • sunstance
    ok at this stage keeping quiet makes no sense as the sun is orange the last phase of our sun we must grow up and see the future for what it is. there is no more time to muck around with what people think the truth is just the truth serves . if there are aliens then there are aliens . it is not cloak and dagger it is we must be able to live with that .
    Reply
  • SpaceNerd-ish
    sunstance said:
    ok at this stage keeping quiet makes no sense as the sun is orange the last phase of our sun we must grow up and see the future for what it is. there is no more time to muck around with what people think the truth is just the truth serves . if there are aliens then there are aliens . it is not cloak and dagger it is we must be able to live with that .


    The Sun isn't actually orange; it's white. I know that we must live with the aliens (assuming there are), but what happens when a human does something wrong and ruins it for everybody else? You still haven't answered that question.
    Reply
  • magnoflux
    The inference in this quote "helped scientists to study how electric currents from Saturn's auroras heats the planet's upper atmosphere, generating the solar wind. " is incorrect as the solar wind is the suns positive ions being attracted from the star to the negative charged enclosures of planetary matter. The planet is linked to the magnetically and spins due to the magnoflux spin effect.
    Reply