Titanic antarctic vortex antics

By Phil Plait | July 11, 2012 6:22 am

The Cassini spacecraft has been orbiting Saturn since late 2004, and has spent most of that time more or less in the same plane as the rings and moons. That allows it to pass close to these interesting places and see them in high resolution.

But scientists and engineers recently changed that, flinging the probe into a more inclined orbit so that it can see things from a different vantage point, literally getting a new perspective on them. For example, from this tipped path, it was able to clearly see the south pole of Titan, Saturn’s ginormous moon – the biggest in the soar system, bigger than the planet Mercury! And what it saw surprised everyone, and for good reason:

Isn’t that weird looking? Like some kind of bacterium, or a cell. In fact, it is a cell, but not the biological kind. It’s an air cell, a vortex, a spinning around the pole. Titan has a thick atmosphere (thicker than Earth’s in fact) and it moves. This cell of air rotates once every 9 hours or so, far faster than Titan’s own 16 day spin. Cassini took enough images to make this animation of the vortex’s motion:

Things like this are seen at the poles of other words; Saturn itself has one, as does Venus. Titan also has a "hood" a haze layer over its north pole. That may be a seasonal feature, and right now winter is coming for Titan’s southern hemisphere*. Perhaps this vortex plays a part in forming the polar hood, and we’ll see one over the south pole soon.

That’s not clear yet, but it may become so as Cassini continues to investigate this incredible system. It’s been there for almost 8 years, and we’ve barely scratched the surface of what’s going on. There’s a whole lot of real estate in the Saturn system, and it changes all the time. We could use 50 Cassinis stationed there, and it still wouldn’t be enough to gather up all the beauty and amazing slices of nature to be seen.

Credits: Video: NASA/JPL-Caltech/Space Science Institute; Music: “Passing Action” by Kevin MacLeod

* Hodor!

Related Posts:

The look of a Titanic moon
Your Cassini awesomeness for today
A window into Titan
Watch out Titan! Vader’s onto you!

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures
MORE ABOUT: Cassini, Saturn, Titan, vortex

Comments (12)

  1. Gary Ansorge

    Wow! 50 Cassinis. That begins to give a little perspective on the size of this system.

    Personally, I’d prefer 50,000…humans, doing this discovery.

    Oh well, guess I’m stuck with just the dream…

    Gary 7

  2. Greg Little
  3. Michael Day

    Could this be one of Carl Sagan’s floating atmospheric alien beasts, smiling for the camera? A giant, gas-filled bacterium.

  4. funkmon

    Is Titan the biggest moon in the solar system? I thought Ganymede was.

  5. Sparky

    Biggest moon in “Soar” system? Well, last time I looked, I thought Ganymede was the largest in the “Solar” system, but you’re talking about something else entirely. 😉

  6. Nigel Depledge

    From nineplanets.org:

    Ganymede diameter : 5262 km
    Ganymede mass : 1.48 E23 kg
    Titan diameter : 5150 km
    Titan mass : 1.35 E23 kg

    Bad BA! Ganymede certainly seems to be the largest moon in the solar system, being larger than Titan by more than 100 km in diameter and by more than 10^22 kg in mass.

  7. Scott B

    We’ve seen polar vortices on Venus, Earth, Mars, Jupiter, Saturn, and now Titan. I’m not sure if we’ve seen them on Uranus or Neptune. I’ve seen conflicting info on that on the web. It’s probable that all planets/moons/bodies with significant atmospheres have this feature though.

  8. Chris A.

    One can claim that Titan is larger than Ganymede if one includes Titan’s atmosphere. That may seem like “cheating,” but one is then forced to ask: “Where’s the ‘edge’ of planets like Jupiter and Saturn, which lack a solid surface?”

  9. Chris A.

    It’s not entirely obvious to me from the images that the rotation referred to is the gas circling every 9 hours, or some sort of superimposed circulating wave. I’m inclined to think the latter. If so then only its shape (long axis, whathaveyou) rotates every 9 hours, but its gas is moving much slower (just as participants don’t circumambulate around the stadium every few seconds whenever the crowd is doing “the wave”).

  10. Nigel Depledge

    Chris A (8) said:

    One can claim that Titan is larger than Ganymede if one includes Titan’s atmosphere. That may seem like “cheating,” but one is then forced to ask: “Where’s the ‘edge’ of planets like Jupiter and Saturn, which lack a solid surface?”

    It seems to me that, where a planet or other body has a solid surface (or even only partly solid, like Earth’s), the surface is the “edge” to use. Where a body has no solid surface (as is the case for Jupiter and Saturn, and maybe Ouranos and Neptune), the cloud-tops mark the “edge”.

    Interestingly, because Pluto has a seasonal atmosphere, using its solid surface gives a constant diameter; using its atmosphere as the edge would make its diameter vary seasonally.

    So, while Titan does indeed have a thick atmosphere, it also has a clearly detectable solid surface.

  11. Matt

    Please remember, what is dead may never die.

  12. Chris A (8) said:

    “Where’s the ‘edge’ of planets like Jupiter and Saturn, which lack a solid surface?”

    One convention I’ve seen used for answering this question is “at what radius does the pressure equal one atmosphere (101.3 kPa)?” Again, it’s really arbitrary, as this convention is based on the average atmospheric pressure on Earth at sea level at 0 degrees Celsius. If we used this convention for Titan (which makes no sense, as it has a solid surface), its radius would increase since the pressure at its surface is 1.5 atm.


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