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NASA Space

Cassini Probe Will Dive Through Enceladus's Water Jets (nasa.gov) 65

An anonymous reader writes: NASA's Cassini probe has a daring mission tomorrow: dive through the water jets spraying from the south pole of Saturn's moon Enceladus. The probe will be a mere 30 miles above the surface, traveling at a relative speed of 19,000 mph. Researchers hope to gain insight into the chemical composition of the jets. "[T]he plumes are more than just gas and water: samples show that they also contain many of the building blocks essential to Earth-like life. This lends itself to the exciting possibility that organisms similar to those that thrive in our own deep oceans near volcanic vents exuding carbon dioxide and hydrogen sulfide might exist on Eceladus." The molecules suspended among the water may tell us whether Enceladus's oceans are capable of harboring life. "The spacecraft's sensors will pick up gases in the plume searching for the presence of molecular hydrogen (H2). The amount of H2 found could reveal how much hydrothermal activity is occurring in the ocean."
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Cassini Probe Will Dive Through Enceladus's Water Jets

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  • Hmm (Score:5, Funny)

    by BigSlowTarget ( 325940 ) on Wednesday October 28, 2015 @02:33AM (#50815283) Journal

    Cool science but it sounds like "Hold my beer and watch this" on a planetary scale.

    • Re:Hmm (Score:5, Informative)

      by Anonymous Coward on Wednesday October 28, 2015 @02:45AM (#50815301)

      It sort of is, but Cassini only has a year or so left in its mission before it is out of propellant needed for adjusting its orbit around Saturn. From here on, missions will get riskier, finishing with the Grand Finale, where it orbits between Saturn and the innermost ring a couple dozen times, before it plunges into the planet to keep from possibly contaminating Enceladus

      • Re:Hmm (Score:5, Funny)

        by nospam007 ( 722110 ) * on Wednesday October 28, 2015 @07:01AM (#50815709)

        "It sort of is, but Cassini only has a year or so left in its mission before it is out of propellant "

        That's why they drive it through the probe wash. Clean probes bring more money with aliens.

      • Seems to me there's just as much chance of interesting chemistry possibly leading to some form of life happening deep down in a gas giant as there is on a small moon.

          • by Viol8 ( 599362 )

            We have no idea what the limitations for self reproducing biochemistry are. I so no physical or chemical reason some form of it couldn't exist further down in the cloud deck.

            • Engineering is all about tradeoffs. Sure, the ideal would be to not crash the probe into any planet. Given what we know, steering into the least-likely place to have life is the least bad decision. What is your proposal?

            • Elements other than hydrogen and helium might be a good thing. Saturn doesn't have much in the way of heavier elements, so how exactly would it work to have life without heavy elements?

              • by calque ( 4296327 )
                By "not much", you mean not much in terms of percentages. But Saturn is kind of large in an absolute sense.
          • by Lumpy ( 12016 )

            Pls the fact that the radiation from saturn on the moons there is pretty freaking nasty. Living inside a 1000watt microwave would be more enjoyable.

        • by necro81 ( 917438 ) on Wednesday October 28, 2015 @09:42AM (#50816331) Journal
          Consider the end scenarios:

          1) Cassini crashes into Enceladus. Because it has no atmosphere to speak of and a solid surface, the spacecraft will impact on the ice and make a real mess. Fragments of the spacecraft may survive, more or less in the condition that they left Earth (although much older), including the plutonium RTGs. Eventually, these may work their way through the ice and into the subsurface ocean, contaminating a fairly interesting environment (the ocean-ice interface and the ocean-crust interface).

          2) Cassini crashes into Titan. Because there is a significant atmosphere, Cassini will burn up to some extent, but some of it, surely, will survive re-entry, distributed over a large area, and thump into the surface. Due to the thick atmosphere and low gravity, the terminal velocity is quite modest (slower than Earth's), so any bits of Cassini that survive re-entry will have a pretty soft landing. This, too, is contamination of a fairly interesting environment (the surface-atmosphere interface, or in the hydrocarbon lakes).

          3) Cassini is intentionally de-orbited into Saturn. Saturn is basically all atmosphere and has no surface to speak of: it'll burn up pretty much all the way down, eventually floating in the deepest parts of the planet that are especially dense enough so that even metals are buoyant. These deep reaches are also really hot, which will at least kill anything still alive or viable on the spacecraft, and probably just melt everything in some extreme chemistry. Compared to permanently scattering the spacecraft across a moon, the amount of time Cassini passes through the various layers of Saturn before reaching its hot death is quite brief. Finally, Saturn is the 2nd most massive planet in the solar system, 10^3 -to- 10^6 times the size of its moons, so any contamination from Cassini will be much more diluted.

          So, considering that getting Cassini out of the Saturn system is not possible, tossing it into Saturn itself seems the best option.
          • by Viol8 ( 599362 )

            "tossing it into Saturn itself seems the best option."

            I would have thought putting it in a parking orbit would have been the best option. That way it could still be used.

  • Rings (Score:5, Interesting)

    by Anonymous Coward on Wednesday October 28, 2015 @02:47AM (#50815305)

    This is great. They're incurring a degree of risk to investigate Enceladus.

    My dream is that one day they'll risk Cassini to get a better look at this [wikipedia.org].

    • My dream is that one day they'll risk Cassini to get a better look at this [wikipedia.org].

      It's too late. That photo was from when Saturn was at equinox, 2007 or so, and therefore the Sun cast long shadows at it's equator (the ring plane orbits Saturn above the equator). Saturn orbits the Sun about once every 30 years, so you've got 15 years between equinoxes (equinoii?). That means the next opportunity to catch those moonlets' shadows at their longest, and to have the leading faces properly illuminated, will be in 2022 or thereabout. Cassini won't last that long.

  • How much kinetic energy is in a drop of water at 19k mph?

    • Re: (Score:3, Interesting)

      by Anonymous Coward

      At "pharmacist drop" of 20 drops per milliliter its mass is 50mg
      19000mph is 8493.76m/s
      The kinetic energy is 1803J.

      Energy of a typical NATO rifle round, 5.56x45 mm is 1796J

      • by Rei ( 128717 )

        But of course these aren't like Earth "water drops", they're more like frozen dust grains.

        Still, potentially destructive.

        There's interesting potential for future missions (almost assuredly ion-powered) to do Enceladus sample return by doing flybys with a carbon collector (better than the silicon aerogel used by Stardust). But for that you have other options than just doing a straight flyby - you could enter a highly elliptical orbit around Enceladus with the apogee - or the ascent - positioned over the gey

  • I guess I didn't realize that satellites would come with an umbrella option. Windshield wipers are standard I guess?
  • Slashdot (Score:4, Insightful)

    by wonkey_monkey ( 2592601 ) on Wednesday October 28, 2015 @04:31AM (#50815425) Homepage

    molecular hydrogen (H2)

    Okay, so you think Unicode is too hard. But why can't we even have <sub> and <super>?

    And yet we can have <code>...

  • by trout007 ( 975317 ) on Wednesday October 28, 2015 @06:26AM (#50815623)

    The EU guys have an interesting take on this. Will be cool to see how charged this geyser is.
    https://m.youtube.com/watch?v=... [youtube.com]

  • There might be life on Ecelandus, and after this close pass, there might be life on the Cassini probe too. So when cassini reaches end of life, it will most likely be crashed in to something, probably Saturn, but does this risk transferring organisms from Ecelandus to Saturn?

    • There might be life on Ecelandus, and after this close pass, there might be life on the Cassini probe too. So when cassini reaches end of life, it will most likely be crashed in to something, probably Saturn, but does this risk transferring organisms from Ecelandus to Saturn?

      Organisms might be transferred to Saturn, but given the conditions there they wouldn't be alive for long.

      • by Anonymous Coward

        Sorry, but you can't possibly know that.

    • I am thinking more about the risk of earth organisms being rinsed off Cassini and falling back to Ecelandus during the pass. I wonder what the risks of that are.
  • is 30 miles even within the margin of error for the trajectory calculations?

    just seems like an extreme risk for a fully functioning probe ... UNLESS ... it's all been an elaborate hoax that JPL is tired of perpetrating so to end it, the probe will be 'lost' in a crash on the moon. The graphics artists who have been involved in the ruse will be 'taken care of', the file will be closed ... until it's discovered one of the artists somehow survived and has decided to go public ... Tom Cruise starring role in

  • ... a trout hits the windshield.
  • by Anonymous Coward

    I seem to remember reading somewhere that what kills most people who jump off tall bridges is hitting the water, its sort of like wet concrete at high speeds. If these are really water jets and not jets of water mist then hitting them with anything traveling at 19,000 mph ( ~8.5 km per second in real numbers) just might cause a bit of a splat. Sort like a giant, high tech bug hitting a windshield.

    • I seem to remember reading somewhere that what kills most people who jump off tall bridges is hitting the water

      Well yes, what else would it be?

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