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Wednesday, March 9, 2011

Tiger, tiger, burning bright

Typically, in astronomy, "The Great Silence" refers to the (not actually surprising) lack of intelligent radio transmissions emanating from the nearby stars.

Today it apparently refers to the lack of intelligent or otherwise radio transmissions emanating from the commercial media regarding the NASA announcement of a high energy heat source on Saturn's moon Enceladus.

By "commercial media" I mean CNN, BBC, Fox and even Weekly World News. I gave up the search after WWN, although I was pleased to learn there that space aliens have been ditching the bodies of human abductees onto the surface of the moon, minus their bones. How DO they keep scooping larger news agencies like the BBC?

Anyway, none of the news outlets I checked had picked up the NASA story (the real one). Given the incredible opportunity this story presents for each of the media outlets to royally eff it up in their own special way, I was inclined to give NASA credit for cleverly hiding the story in plain sight and wording it so blandly that the media didn't notice it. But that would imply that the NASA press corp was "clever", and so far the available data does not fit that hypothesis very well.

My next hypothesis was that the news outlets did read the story and understand its implications, but were taking the responsible path of allowing the information to trickle into the public's consciousness in its own time. Then I remembered that I had included Fox News in my list.

The only conclusion I was left with was that the science editors of the various media really genuinely didn't understand the importance or the implications of the press release. So, allow me to break it down into itty bitty words for the journalists.

Saturn has a tiny moon called Enceladus. "Tiny" as in about 500 kilometers, or about 300 miles, in diameter. For comparison, if Enceladus happened to be sitting on Ellensburg WA, the sphere of the moon would reach to Aberdeen WA to the west, Pullman WA to the east, Warm Springs OR to the south and nearly to Chilliwack BC to the north. So, "tiny" as far as moons go, but you wouldn't want to have to store it in your basement.

Enceladus has an ice mantle which is about 5km thick, which is much thinner than the ice mantles of the Jovian moons. Beneath that is a salt water ocean, which happens to be rich in simple organic chemicals.

Now, here's the rub. Enceladus should be frozen solid. There really isn't a logical reason why the interior of Enceladus is warm enough to melt the ice. There are two standard candidates for this, the first being tidal expansion and contraction from the gravitational relationship with Saturn and Dione (another of Saturn's moons), and the second being radioactive decay of superheavy metals within the rocky interior of Enceladus. Neither of these explanations hold much water.

Mimas, yet another of Saturn's moons, is closer still to Saturn but frozen stone cold solid. And you wouldn't really expect a world with a gravity 0.01 times that of earth to have made very much uranium.

Furthermore, Enceladus' heat does not seem to be evenly distributed around the globe, but concentrated in one single very small area. A tidally induced underwater volcano might account for this, but we would expect that to be situated near the equator, either facing or opposing Saturn (like our own moon, Enceladus is tidally locked with Saturn, with the same side always facing the planet). However, it turns out that our lone hot-spot is precisely at the south pole.

Still, knowing that there was in fact a hot-spot, scientists computed the absolute maximum heat output which could be generated by a combination of tidal dynamics and radioactive decay. The very generous number they arrived at was 1.4 gigawatts.

The hot-spot is called the "tiger stripes", because it is a region of four nearly parallel and evenly spaced trenches, each about 80 miles long by 1 mile wide. Cassini recently measured the heat from the tiger stripes as 15.8 gigawatts. More than ten times the maximum which could be generated by any known natural phenomenon.

So, what are we looking at here?

The official SWAG (stupid wild-assed guess) from NASA and JPL is that it is a somehow anomalous flareup that Cassini just happened to capture. The problem with this is that the original 1.4 gigawatt number was the anomalous flareup. So we can probably throw that one out. That leaves us with two possibilities. Either we're seeing a previously unknown natural phenomenon, or we're seeing a previously unknown artificial phenomenon. Either way we're going to need a lot more data and a lot more research. And suddenly Saturn's moon system looks a lot more interesting.


  1. "A previously unknown artificial phenomenon."
    That's coy.


    Or Enceladus itself is the spaceship and the Tiger Stripes are some kid of thermal vent. Obi Wan said it: "That's no moon..."

    Blog on, brother!

  2. Hello,

    I'm not quite ready to "boldly go" there yet. There are some possibilities which don't involve space aliens.

    One thought I had last night was that it could be something like the Oklo natural nuclear reactors in Gabon, 2 billion years ago. But these yielded something like 100 kilowatts of energy as opposed to nearly 16 gigawatts. And, it seems unlikely to me that any quantity of uranium would have formed on a world that small.

    I was also trying to think of any natural chemical reaction which could yield that amount of heat, but as far as I know there just isn't any.

    As far as gravitational or any other effect from Saturn, anything Enceladus can do Mimas should be doing better, but we categorically are not seeing that.

    So at this point, the possibility that it is a non-terrestrial artifact does warrant consideration.

    For whatever it's worth, other than its very high albedo and general smoothness Enceladus does not appear greatly different from all of the other icy moons in the solar system. So, the "Death Star" hypothesis seems pretty unlikely to me. Enceladus is, from all appearances, just the tiny icy moon it seems to be. The only major anomaly is the heat signature at the south pole. But that heat source is huge; if it is in fact a single object then it's apparently 80 miles in diameter or 80 miles on a side, depending on whether the warm patch is seen as a circle or a square. It's also possible that we're looking at four distinct elongated heat sources lying neatly parallel to each other. We just don't have enough data right now to know.

    Cassini's schedule has it focusing on Titan for the next several months. Then on October 1st it will do a low altitude (99 kilometers, or 62 miles) flyby of Enceladus' south pole, followed by two more higher altitude flybys on October 19th and November 6th. The October 1st flyby is the one to watch. Either the tiger stripes will have cooled and the earlier heat signature was a transitory event, or they are still warm, or warmer, meaning...something.

    Either way we'll know more in October, and I'll definitely be tracking it here.


    You can say it any scientific and pretty way you like, but it's walking like a duck and quacking like a duck and laying eggs like a duck and swimming like a duck. I really think it's probably a duck.

    Occam's Razor, sailor. Occam's razor.

  4. Alright. Game, set and match.

    And for the record, my first impression (and my continuing impression) is that your assessment is at least as likely as any other possibility, and probably moreso.

    In fact, my original plan for this post was to write a very dry and analytical description of what Cassini found, and intersperse it with screen caps from the first X-Files movie of the giant spaceship in the Antarctic ice. Without comment.

    But I'm still going to be looking for "natural" explanations for the tiger stripes, if only to eliminate them. Because whatever is going on up there, it's something awfully interesting.