Ganymede, Jupiter’s Moon, Has Massive Ocean: NASA

NASA scientists have found strong evidence of a saltwater ocean under the icy surface of Ganymede, Jupiter’s largest moon. The discovery suggests that Ganymede could potentially support life as we know it. Using data from the Hubble Space Telescope, NASA found that the subterranean ocean holds more water that all of the water on Earth’s surface.

Ganymede, Jupiter's Moon, Has Massive Ocean: NASA

Ganymede has long been suspected to contain water

John Grunsfeld, the assistant administrator of NASA’s Science Mission Directorate, said it was a “significant milestone.” He said the discovery of a deep ocean beneath the icy crust of Ganymede opens up “exciting possibilities for life beyond Earth.” Ganymede is the largest moon in our solar system. It is the only moon in the solar system that has its own magnetic field.

Jupiter’s largest moon has long been suspected to contain water. Researchers first suspected the presence of the ocean on Ganymede in 1970. In 2002, NASA’s Galileo mission provided the first evidence supporting these assumptions. Now, Hubble Space Telescope has found compelling evidence. Scientists believe that its ocean is buried under a 95-mile crust of ice. Ganymede’s saltwater ocean is 60 miles thick, almost 10 times deeper than the Earth’s oceans.

How NASA determined the presence of water

Ganymede’s magnetic field creates ribbons of glowing, hot electrified gas, called aurorae, in regions circling the north and south poles of the moon. The moon is pretty close to Jupiter, so it’s also embedded in Jupiter’s magnetic field. The aurorae on Ganymede change, rocking back and forth, when Jupiter’s magnetic field changes.

The changes in aurorae helped scientists determine that there was a massive saltwater ocean under Ganymede’s crust, affecting its magnetic field. In the presence of a saltwater ocean, Jupiter’s magnetic field creates a secondary magnetic field in the ocean that counter’s Jupiter’s magnetic field. This “magnetic friction” significantly suppresses the rocking of the aurorae.

Scientists said Ganymede’s ocean fights Jupiter’s magnetic field so strongly that the rocking of the aurorae is reduced to just 2 degrees, compared to 6 degrees if the saltwater ocean were not present.

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  • James Wood

    Your inability to grasp the materials is not a failing on my part.

  • americanparser

    Clearly, you did not read the links, or you would know that they disagree with your rigid definition of a theory, not mine. The only thing I clearly do not is agree with you on this issue.

    If that “you, caveman, me, erudite” drivel keeps you comfortably out of the way of anything that might question your sacred cows, then have at it. The Pillars of Science are most famous for one thing: crumbling. But you go ahead and chain yourself to them. I would hold on to that key, though.

  • James Wood

    I am sure they know what a theory is. You, clearly, do not.

  • americanparser

    Well, then, I guess the graduate-degreed scientists I referenced in the links aren’t scientific, either.

    You see, James, the difference between you and me is that I can admit that legitimate scientists can operate under sincerely held, studied, and yet diametrically opposed paradigms and still be called scientists, whereas you can’t imagine any real scientific inquiry outside of the construct you’ve been taught. And that’s a shame, because real scientific inquiry moves only as freely as we feel free to question it. But whatever, James. This is where we started, isn’t it? Let’s just agree to disagree and call it a day. Feel free to chime in with the last word, man. Peace out.

  • James Wood

    You claim an education, yet do not understand what a theory is. If you are educated, your education is not scientific.

  • americanparser

    My education, James, affords me the luxury of debating by point instead of insult, which I guess is more than yours is affording you. You can do better than lob website links without an original thought to accompany them. I know you can, James.

  • James Wood
  • Guest

    In the reference above citing the 1828 Webster’s dictionary, I intended to say “founded,” not “found.”

  • americanparser

    It is mildly comical how quickly supposedly educated persons resort to decidedly unscholarly language and gradeschool ad hominem attacks when their indoctrination hits a wall.

    James, theories have not been tested and validated in every way possible. If they all had been, the scientific community would still be upholding the Theory of Spontaneous Generation, the Caloric Theory, and the Steady State Theory. Theories can be good working explanations, but they are not incontrovertible.

    This is why Webster’s 1828 Dictionary says that theories are founded upon INFERENCES upon principles, which are in turn themselves based on independent evidence.

    It’s why Merriam-Webster Dictionary describes theories as PLAUSIBLE.

    It’s why Oxford, that last bastion of creationist fraudsters, defines theories as SUPPOSITIONS, which, again, according to Oxford, are UNCERTAIN BELIEFS.

    Lastly, Professor William K. Tong (, a 20 year veteran geologist with the Environmental Protection Agency, makes the point best at He says that while theories are certainly “well-tested, well-documented explanations… that (are) supported overwhelmingly by valid data,” nonetheless, “there are rare examples (so, examples are rare) of scientific theories that have successfully survived all known attacks for a very long time, and are called scientific laws,” and that at the end of the day “a theory is subject to modification and even rejection if there is overwhelming evidence that disproves it and/or supports another, better theory. Therefore, a theory is not an eternal or perpetual truth.”

    A hypothesis is a relatively untested explanation that might work. A theory is a tested explanation that works so far. A law is an explanation that has worked so consistently for so long that we expect it always will.

    So, James, you do get better than a theory. You get scientific law, or, some would say, a fact. Maybe someday, scientific law will prove that there is a saltwater ocean on Ganymede. But right now, my friend, that is just a theory.

  • James Wood

    False. A theory is tried and true. tested in every way possible by every applicable branch of science.
    In science, you do not get better than a theory. This is a very difficult to reach status. It means the concept has been tested time and time again for decades, and has held true through every attempt to disprove it.
    Drop the “observable” bullshit that comes from the creationist fraudsters. It is a lie by omission. There are many many many many ways to gather evidence, direct observation being but one of them. It is one of many, not the only option. If it were, forensics would not work.

  • americanparser

    A scientific theory, in modern terms, is neither a wild guess, nor a fact. A scientific theory is a set of as yet unproven but possible explanations that make the scientific establishment comfortable with its current cosmic paradigm. That might make it useful to some degree for political support and funding, or even for practical application, but that expedience does not make the theory a fact.

    No one has seen, heard, touched, tasted, or by any other means observed an ocean of water on or beneath the surface of Ganymede. Theorizing a large ocean as existent to explain actual observable phenomena is perfectly acceptable, but until someone observes that ocean and eliminates all other reasonable possibilities that might explain the unique behavior of Ganymede’s aurorae, the idea of the ocean around Ganymede is not a fact.

  • James Wood

    In science, a theory is a fact. theory does not mean wild assed guess.

  • americanparser

    So this is a theory, not a fact. A saltwater ocean has not been discovered on Ganymede; a theory of a saltwater ocean has been proposed to explain the seemingly peculiar characteristics of Ganymede’s aurorae. No ocean has been directly observed.