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Finding Jupiter’s Water

One of the memorable things about 1995 (and this was also the year of the first detection of an exoplanet around a main sequence star) was the release of the Galileo spacecraft’s descent probe. Dive into that howling maelstrom, it would seem, and instant obliteration should follow. But the probe had been designed with a heavy duty heat shield to protect it during its journey. It kept transmitting after scorching its way into Jupiter’s atmosphere at 47 kilometers per second, 30 km/sec faster than Voyager 1. The probe returned data for fully 58 minutes before its demise.

Here’s how two science fiction novelists handle a descent into the Jovian clouds:

Slowly, the fine fretwork of the ammonia cirrus clouds above him became obscured by brown and salmon layers of intervening chemistry, the air stained a nicotine-coloured haze of complex carbon molecules. Soon it was warmer than a summer’s day out there, and already the gondola was enduring more than ten atmospheres of pressure, the structure making slight creaking sounds as it absorbed the mounting forces. Falcon eyed the hull around him with a certain wariness, trusting that the Kon-Tiki’s molecular-scale refurbishments had been as thorough as claimed.

A certain wariness seems justified. And this:

Overhead, the sky was darkening through shades of purple. This was not the onset of evening — dusk was still hours away — but the gradual filtering out of solar illumination. Much the same thing happened in the depths of Earth’s oceans. The main difference here was that the external temperature was steadily rising, even as the iron crush of the atmosphere redoubled its hold on the gondola.

That’s Stephen Baxter and Alastair Reynolds in The Medusa Chronicles (Saga, 2016), which picks up on Arthur C. Clarke’s 1971 novella “A Meeting with Medusa,” and takes its hero into the heart of Jupiter, the earliest part of which descent is glimpsed in the paragraph above. Doubtless Baxter and Reynolds were all over the Galileo data as they made the transition between what we know to the ingenious plot they constructed. Galileo’s data had their share of surprises, showing us, for example, stronger winds than expected, but that was just a start for the adventures of the book’s hero.

Let’s leave science fiction for the moment, though I’ll come back to it. The region the Galileo probe descended through turned out to be drier than expected, another Galileo surprise given that ice is the primary constituent of Jupiter’s moons. Now we have new work delving into the question of water on Jupiter. A team led by Gordon Bjoraker (NASA Ames), working with collaborators at several US universities, suggests in a paper in The Astronomical Journal that water is detectable and it may be out there in large quantities indeed.

While Jupiter’s atmosphere is 99 percent hydrogen and helium, it could still contain many times the amount of water we have on Earth. The scientists probed the question using data gathered by ground-based telescopes to detect traces of water deep within Jupiter’s Great Red Spot, working with the iSHELL spectrograph at the NASA Infrared Telescope Facility and the Near Infrared Spectrograph on the Keck 2 telescope (both instruments are at Mauna Kea in Hawaii):

In this paper we present ground-based observations of Jupiter’s Great Red Spot between 4.6 and 5.4 µm. The 5-µm region is a window to the deep atmosphere of Jupiter because of a minimum in opacity due to H2 and CH4. This spectrum provides a wealth of information about the gas composition and cloud structure of the troposphere. Jupiter’s 5-µm spectrum is a mixture of scattered sunlight and thermal emission that varies significantly between Hot Spots and low-flux regions such as the Great Red Spot.

Image: Trapped between two jet streams, the Great Red Spot is an anticyclone swirling around a center of high atmospheric pressure that makes it rotate in the opposite sense of hurricanes on Earth. Credit: NASA/JPL/Space Science Institute.

The Great Red Spot is an enormous storm that, though mutable, has continued to rage for at least 150 years and perhaps much longer than that. The researchers found evidence of three layers of clouds here, with the deepest at 5-7 bars (1 bar approximates the average atmospheric pressure at sea level on Earth). This would be about 160 kilometers below the cloud tops in a region where temperature is thought to reach the freezing point of water. The Bjoraker team describes an opaque cloud layer detected at around 5 bars as ‘almost certainly a water cloud.’

What’s crucial here is the methodology, because if the methods used on the Great Red Spot can be validated by the Juno spacecraft, we can apply them to other gas giants. Now orbiting Jupiter until 2021 and conducting its own search for water using its infrared spectrometer, Juno has as a key objective the identification and characterization of atmospheric H2O, although observations using the spacecraft’s Microwave Radiometer are tricky given the low microwave absorptivity of H2O gas when compared to ammonia.

Thus we have a necessary synergy between ground-based measurements of both H2O and NH3 to support what Juno’s MWR instrument finds and to increase the accuracy of its calibration. This Clemson University news release explains that within months, the team will be collecting ‘many gigabytes’ of data with the iSHELL spectrograph that can be matched against further Juno observations, with a suite of automated software being built to analyze the results.

Getting a better picture of Jupiter’s water content could prove useful in a number of ways, and might even take us in a science fictional direction, says Clemson University co-author Máté Ádámkovics:

“The discovery of water on Jupiter using our technique is important in many ways. Our current study focused on the red spot, but future projects will be able to estimate how much water exists on the entire planet. Water may play a critical role in Jupiter’s dynamic weather patterns, so this will help advance our understanding of what makes the planet’s atmosphere so turbulent.”

True enough. And this takes us back into the imaginative realm of Clarke, Baxter and Reynolds:

“And, finally, where there’s the potential for liquid water, the possibility of life cannot be completely ruled out. So, though it appears very unlikely, life on Jupiter is not beyond the range of our imaginations.”

For those wanting to explore notions of life within Jupiter’s atmosphere, have a look at Larry Klaes’ fine essay Edwin Salpeter and the Gasbags of Jupiter, which looks at a Cornell University collaborator of Carl Sagan and the duo’s unusual musings on a Jovian taxonomy.

The paper is Bjoraker et al., “The Gas Composition and Deep Cloud Structure of Jupiter’s Great Red Spot,” The Astronomical Journal Vol. 156, No. 3 (abstract).


{ 11 comments… add one }
  • Michael Fidler August 31, 2018, 14:33

    The gasbags of Jupiter I believed was the first illustrations of what life might be like on a completely alien worlds compared to earth type planets. I’m just wondering if any of the material thrown up by the Shoemaker-Levy comet impact was shown to be water? The impacts where so inky black that it looked like you where looking into a deep abyss.

    Some interesting news about water worlds and there ability to support life:

    Habitability of exoplanet waterworlds.
    Edwin S. Kite, Eric B. Ford

    “We model the evolution of ocean temperature and chemistry for rocky exoplanets with 10-1000× Earth’s H2O but without H2, taking into account C partitioning, high-pressure ice phases, and atmosphere-lithosphere exchange. Within our model, for Sunlike stars, we find that: (1) habitability is strongly affected by ocean chemistry; (2) possible ocean pH spans a wide range; (3) exsolution-driven climate instabilities are possible; (4) surprisingly, many waterworlds stay habitable for >1 Gyr, and (contrary to previous claims) this longevity does not necessarily involve geochemical cycling.
    We also find, using an ensemble of N-body simulations that include volatile loss during giant impacts, that a substantial fraction of habitable-zone rocky planets emerge after the giant impact era with deep, ice-free water envelopes. This outcome is sensitive to our assumptions of low initial abundances of 26Al and 60Fe in protoplanetary disks, plus H2-free accretion. We use the output of the N-body simulations as input to our waterworld evolution code. Thus, for the first time in an an end-to-end calculation, we show that chance variation of initial conditions, with no need for geochemical cycling, can yield multi-Gyr habitability on waterworlds.”


    Water worlds could support life: Analysis challenges idea that life requires ‘Earth clone’


  • Alex Tolley August 31, 2018, 14:52

    A small note: The Medusa Chronicles is by Stephen Baxter and Alistair Reynolds. I really enjoyed the exploration of Clarke’s basic concept in A Meeting with Medusa. Baxter had done this before with The Wire Continuum a collaboration with Clarke based on Clarke’s very early short, Travel by Wire. Personally, I found the Clarke-Baxter novel collaborations less than successful. The Baxter-Reynolds collaboration with The Medusa Chronicles was far better.

    • Paul Gilster August 31, 2018, 15:55

      I’ll add Alastair Reynolds into the text right away. Can’t believe I forgot that — he’s a personal favorite!

      • ljk September 10, 2018, 9:59

        An article from 2016:

        The Juno space probe is now in orbit around Jupiter, meaning space buffs around the world are eagerly awaiting whatever new data the probe sends back. One of those space buffs is science fiction author Stephen Baxter, who recently collaborated with Alastair Reynolds on the novel The Medusa Chronicles. The book is an authorized sequel to Arthur C. Clarke’s famous 1971 novella “A Meeting with Medusa,” about an astronaut who discovers intelligent life on Jupiter.

        “All this comes from Carl Sagan, the great astronomer, who hypothesized that somewhere in Jupiter’s deep cloud layers … you could have a great ocean, a gaseous ocean, where gigantic creatures could live,” Baxter says in Episode 211 of the Geek’s Guide to the Galaxy podcast.

        Full article here:


        To quote:

        “A Meeting with Medusa” imagines human exploration of Jupiter in 2099. That may have seemed reasonable back in 1971, but these days it’s looking pretty unlikely. For The Medusa Chronicles, Baxter and Reynolds were obliged to invent an alternate timeline to justify the dates in Clarke’s original story. Still, Baxter says that Clarke wouldn’t be too disappointed that we haven’t lived up to his predictions.

        • ljk September 10, 2018, 10:04

          Let us not forget Ben Bova’s SF novel from 2000 titled Jupiter. He envisioned giant whalish beings floating in Jupiter – not its atmosphere but in a huge layer of liquid water below it.


          Speaking of Clarke, in the novel 2010, there was mention of alien creatures floating in the Jovian atmosphere, but the Monolith ETI decided the ones on Europa had a better chance of becoming truly intelligent, so they carried on with their plan to turn Jupiter into a sun.

  • Rob Flores August 31, 2018, 23:35

    Considering the shearing power of Jupiter’s winds, I would think
    that if there are icy/water “atolls” they would function much like
    pools of safety/food that life forms would ambulate to. Life would be Guided there by sensory cells with an affinity for water molecules. I am not sure
    about rotund gas bags as best animal plan for Jupiter life. More likely streamlined
    eel like body plan would make for a better mobility perfomance
    and station keeping.
    But this a very low probability event. More likely is finding microbial
    life on Venus’ clouds, or even on subsurface ice/lake on Mercury’s poles.

  • James Franklin September 1, 2018, 0:43

    Interesting, and difficult to believe it’s been 23 years. What always amazed me was that given the highly complex nature of the Jovian atmosphere, that copies of the decent probe where not created and sent to Jupiter. To me it makes perfect sense to have sent around 10 decent probes to various locations within the mighty planet to get a better picture. What we have done is the equivalent of landing in the Sahara and assuming the Earth is a desert.

    Further, economies of scale dictate that several of these probes could have been constructed and sent to Saturn, Uranus and Neptune so we begin to build a clearer understanding of these world’s too.

    With each probe being unique we increase overall costs, but by making a “production line” probe for specific tasks we can increase efficiency and lower overall costs whilst at the same time increasing our knowledge 100 fold.

  • Patient Observer September 4, 2018, 11:04

    Put a camera on the next probe! And make it a heated balloon (even if chemically heated for a few days) to float around for some good views as it slowly descends. Not sure about how to maintain radio communications but perhaps a direct radio contact with Earth would be feasible. One could imagine a radio-isotope generator charging a battery to power a relatively high power transmitter for an hour per Jovian day. Something like that (with a little handwavium).

  • Gideon Marcus September 4, 2018, 11:27

    This, of course, of paramount importance to me since gas giant diving features prominently in my novel. :)

    Interesting synchronicity, Poul Anderson wrote about gas giant diving 55 years ago (the stories aren’t very good, though…)

  • Patient Observer September 5, 2018, 12:17

    Could not resist the comment that earth is already populated by semi-intelligent giant gas bags.

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