Monday, August 15, 2011

Saturn's Mystery Moon from Lamont Wood

Anomalies are the focus of our recent release Out of Place in Time and Space by Lamont Wood. There are many examples of items and artifacts showing up decades and centuries before they could possibly have been invented. Below we share an excerpt from Chapter 8 which looks at Astronomical Candidates specifically focusing on Saturn's Mystery Moon.

Of course, it’s monumental hubris to say that an astronomical body is out of place, either in time or space. After all, there it is. The laws of physics that govern its motions and other behaviors are known with precision. Space probes can be made to rendezvous with it. As for how it got there, detailed scientific theories explain the whole process back to the Big Bang, possibly beyond. For generations people have been complaining (or gloating) that science has removed the necessity of God, except perhaps as the Cosmic Billiards Player who put the balls in motion. Etc.

Excuse me—the real hubris is in accepting the previous paragraph without blinking. For millennia we have gazed at the stars with nearly total incomprehension, and things are only superficially better today. Meanwhile, what facts we have been able to piece together concerning the nature of the cosmos are totally at odds with our daily experience. But not only are we able to live in comfortable denial about them, we may be better off doing so.

Trivial example: if you got up early enough this morning you were able to see the sun rise gloriously in the east, its rosy fingers touching the clouds across a background that was fading from dark to pale blue. Alas, in truth the sun didn’t rise—the Earth on which you were standing rotated in such a way that the sun came into view. You (hopefully) knew that, but the illusion of the sun rising is too persistent to disregard. Nor is there any reason to disregard it. No one gets confused, or accuses you of trying to mislead them, if you refer to the sun rising. In fact, if you insisted on referring to the Earth as rotating under us, or corrected other people who referred to the sun rising, you might not get an entirely favorable response.

In other words, it is accepted without discussion that we are better off ignoring selected information about this prosaic topic. Describing it in full involves too much information, and some of it is disquieting. If we thought them at length, our equilibrium might suffer. For most of us, celestial mechanics is out of place.

As it turns out, our relationship with a couple of places in the Solar System has been entirely based on decisions to ignore disquieting information. They’re undeniably out there, but our equilibrium would suffer if we thought about them at length. In terms of a cosmos that satisfies our need for pat explanations, they are out of place.

Saturn’s Mystery Moon

Three-quarter-lit Iapetus showing the mysterious dark spot that covers nearly an entire hemisphere, and the equally mysterious equatorial ridge that extends in a straight line across the dark spot. Image courtesy NASA/JPL/Space Science Institute.

Perhaps awesome mysteries await anyone who examines any natural phenomenon in sufficient detail. But you don’t have to delve very deeply to have that experience when talking about Iapetus (eye-Ap-a-Tus), the outmost of the large, prograde moons of Saturn. It is 914 miles in diameter and orbits Saturn at a distance of 2.2 million miles. The fact that it is large enough to be spherical and has a prograde orbit (that is, its orbital travel is in the same direction as Saturn’s day-night spin) and indicates that it was formed with that planet—it’s a “regular” moon of Saturn. (The next section examines the significance of “prograde” and “regular” moon.) Iapetus differs from Saturn’s other regular moons by its rather large orbital inclination, of more than 15 degrees. And while that inclination is a mystery, that’s not the mystery (actually, mysteries) we’re talking about.

The first mystery involving Iapetus is that, when it was first discovered, it was observed to disappear and reappear. Large astronomical bodies are, of course, not supposed to do that.

The moon was first observed in 1671 by pioneering Italian-French astronomer Giovanni Cassini. After figuring its orbit and following it for a number of months, he realized that he could see Iapetus when it was on one side of Saturn, but not when it was on the other side. It was a time when irrational factors were still given credence in the public mind—the Salem witch trials were 20 years in the future, to give one small example. But Cassini was a man of science and would have none of it. He immediately assumed that Iapetus had a bright highly reflective side and a dark, non-reflective side. Meanwhile, he assumed that it revolved only once during its orbit around Saturn, meaning that one side always faced Saturn. Therefore, he could see Iapetus only when it was positioned so that its bright side faced Earth, which was during half its orbit around Saturn. During the rest of its orbit its dark side faced the Earth and Iapetus could not be picked out of the dark background of space.

He could point to the example of the Earth’s Moon, which is locked in position so that one side always faces the Earth. And he knew that the power of available telescopes was a moving target, and what could not be seen today might be seen with a better telescope tomorrow. But that did not mean that the thing which could not be seen did not exist in the meantime.

Basically, better telescopes let you see dimmer objects—ones with lower “apparent magnitude.” The apparent magnitude refers to the brightness of an object when seen by an observer on Earth, and takes no account of how brilliant the object would be if you were nearby—that would be its “absolute magnitude.” Extremely bright stars that are far away will have low apparent magnitudes, even though they may have high absolute magnitudes.

However, in the magnitude scale used by astronomers (both apparent and absolute), dimmer objects are assigned higher numbers. Apparent magnitude 1 is a bright star, while magnitude 6 is about the faintest star that can be seen with the unaided eye on a dark, clear night. (In the night sky of a city, you might not be able to see anything dimmer than 3, as dimmer stars than that are washed out by the background glow.) Values higher than six will require a telescope, and the higher the value the fancier the telescope will have to be. On the other end of the scale, objects brighter than 0 are given negative values.

For example, the Pole Star (Polaris) is about 2, Sirius is -1.4, Venus at its brightest is almost -5, and Jupiter and Mars at their brightest are almost -3. The full Moon is almost -13.

When Cassini found Iapetus, it had an apparent magnitude of 10—when he could see it. He kept the faith for more than 30 years, assuming he could eventually find it when he had equipment that was good enough. That finally happened in 1705, and he found that its dim side had an apparently magnitude of 12. Because each full level of magnitude is about 2.5 times brighter (or dimmer) than the next, the bright side of Iapetus turned out to be more than six times brighter than the dark side. That’s an average based on whole hemispheres. Modern measurements show that its dark areas are as dark as fresh asphalt, while the bright areas are as bright as arctic ice, or ten times more reflective.

So Cassini had demonstrated a rational explanation—except that it was not really an explanation, because there was no obvious mechanism for producing the bright-dark difference. Also, why isn’t the division observed with any other moons?

True, it might result from some kind of sand-blasting effect because, with one side always facing Saturn, another side a quarter-turn away would always be facing the direction of orbit. Saturn has obvious rings, so maybe there is a lot of debris even out in the vicinity of Iapetus, which orbits 1.9 million miles beyond the rings.

Meanwhile, the idea of this moon amounting to an unexplained blinking light in the Solar System intrigued more than one writer, which brings us to Iapetus’ impact on popular culture: Iapetus was the objective of the space mission described in the 1968 Arthur C. Clarke novel, 2001: A Space Odyssey. (The novel was adapted from a 1951 short story by Clarke titled, “Sentinel to Eternity.”) Explorers on Earth’s Moon find a buried monolith that is obviously artificial, and when sunlight first falls on it after excavation it beams a radio message to Iapetus. When an astronaut gets to Iapetus to investigate (surviving an on-board computer’s murder of the rest of the crew) he finds a “gate” that allows interstellar travel.

In the enigmatic movie adaptation, the moon is switched to Jupiter, because a visually convincing movie version of Saturn’s rings proved too difficult.

A real, albeit unmanned spaceship did reach Iapetus in 2007, six years later than Clark’s projected date and 10 years after the probe—called Cassini—was launched jointly by NASA, the European Space Agency, and the Italian Space Agency. Having achieved orbit of Saturn in 2004, it performed a close pass of Iapetus in 2007.

As predicted, its pictures showed that a large part of one hemisphere was covered with a dark spot, not unlike a thin layer of soot. They named the dark spot Cassini Regio. The rest of the surface appears to be ice, and the border with Cassini Regio is abrupt, with no intermediate gray areas. If the dark spot was caused by scouring space debris, you’d expect Iapetus to wobble somewhat in its orbit, and so the darkness would have a feathered edge. The abrupt border makes it seem that the dark material was deposited in one incident, such as an explosion.

Within Cassini Regio, exactly following the moon’s equator, is a pockmarked ridge of mountains, running straight as a garden wall, that’s 12 miles wide and 8 miles high. It’s so obvious in the space probe photos that commentators said it makes the moon look like a walnut. The ridge does not extend beyond the dark spot. (Before someone runs off and says the range is a military fortification that was defeated by the explosion that caused the dark spot, let’s say that the mountains don’t look artificial. They do look like a mountain range, with foothills, rather than a wall.)

Meanwhile, the moon’s shape is oblate, the poles being somewhat flattened. The degree of flatness there, considering that the moon is almost entirely ice, would indicate that Iapetus spins every 10 hours. But it doesn’t—it spins at the same rate that it orbits Saturn, or once every 79 days.

Basically, it looks like Cassini Regio was seared by a huge explosion (military or otherwise) but that does not explain the oddly limited equatorial mountain range, of the polar flattening. The best that can be said is that Iapetus has had an eventful history, one we may wish to understand, as we live in the same Solar System.

Like Giovanni Cassini, we should assume there’s a rational explanation, even as Iapetus continues to produce phenomena that confounds us. But we may also have to accept the possibility that we may not understand Iapetus for the foreseeable future—it may be the ultimate reverse anachronism from the future.

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