I got a little bit of feedback from my Iapetus entry so I'm going to put some more up now.
First up is this one at New Scientist:
Freire, of the Arecibo Observatory in Puerto Rico, thinks otherwise. Because both the ridge and the dark coating are on the same side of the moon, he thinks that they are linked. Freire argues that both features formed when the moon collided with the edge of one of Saturn's rings a long time ago. "I was looking at the Cassini pictures, and the idea suggested itself to me," he says. According to Freire, debris from the ring smashed into a narrow region along the moon's equator, piling up to create the ridge. Consistent with his claim that the moon only grazed the ring is the fact that the ridge does not extend over the entire hemisphere. If the moon had fully entered the ring, a ridge would have formed over a 180-degree arc of the equator, he argues.
Freire also contends that the energy from the impact evaporated the icy parts of the ring's debris, producing a local atmosphere consisting mainly of water vapour. On a moon otherwise devoid of any atmosphere, the vapour rapidly spread towards the north and south poles, creating a temporary wind. This wind deposited debris over the leading face of the moon, creating its enigmatic dark side. The dark coating appears to get thinner the closer it gets to the poles, which supports this idea (www.arxiv.org/abs/astro-ph/0504653).But Larry Esposito, a specialist on planetary rings at the University of Colorado inBoulder, points to a major flaw in Freire's idea. Today, Iapetus's orbit is far outside Saturn's rings and not even in the same plane as they are, making it unlikely that Iapetus ever collided with a ring, he says.
Freire admits that the moon's orbit is a headache. "This is quite hard to solve," hesays. "Unless there have been large orbital changes, I don't see how a collision with a ring can ever have occurred." He suggests that Iapetus was initially closer to Saturn than it is now, but somehow migrated into a higher orbit, possibly because of an encounter with another moon.
According to Porco, Freire "gets high grades for imagination". She believes that the ridge is a tectonic feature - though no one can explain how it formed - and that the coating may be the result of Iapetus ploughing through a dark cloud of cometary debris.
Right. So there are explanations other than Alien Civilization, thank you very much. I am satisfied that it is acknowledged to be shaped like a wallnut and is two tone.
Here's a public discussion forum. Sagely a 'guest' writes:
A giant walnut of course.
Here's a link to a guy who has made images from the RAW data. Make sure to check out his images; He writes:
Straight Lines in Nature? - This is the same image above, contrast enhanced to show detail in the dark area. Continuing a tradition established by Mimas, Iapetus has a large crater reminiscent of the Death Star's weapon dish, only on this moon, the equatorial trench (actually a ridge) appears also. This is really strange, since long straight lines are rare in natural formations. The ridge/trench on Iapetus is part of a great circle, which appears straight when viewed from above as in this image. This arc crosses over half of the circumference of the moon. It also nearly evenly splits the dark area. Are the two related? This remains to be seen, though a correlation of two never seen elsewhere types of features begs for more than chance. (Some of the blockier splotches in the dark region are JPEG artifacts that have been enhanced, unfortunately, along with the real features.)
and...
Cassini Regio and the Great Wall - This mosaic is composed of images taken on December 31, 2004, near Cassini's closest appreach to Iapetus on that date. The resolution is about one kilometer per pixel. It shows Cassini Regio and some of the light bordering areas. It can be seen in the bordering areas that dark material appears to streak away from craters in generally one direction. This kind of pattern is seen in places where wind blows, such as Mars, but Iapetus does not nor is likely to have ever had an atmosphere. The most obvious feature in Cassini Regio is the "straight line", a mountain range that follows a great circle and looks like the dorsal ridge on an animal. The mountains are nearly ten kilometers tall at the horizon, taller than any mountain on Earth. The overall appearance of the moon suggests a hypothesis that Iapetus cracked open and volatile material erupted out and covered the region around the crack, perhaps suddenly, perhaps over a very long period. In large craters further from the ridge, landslides of white can be seen, suggesting that cliffsides broke loose, exposing white material underneath. The confirmation of any hypothesis will likely require high resolution images of crater rims, the central ridge,
and the regions that look "windblown".
I don't know what to make of all this - which is why I'm putting it out here.
There's a dirty big 'wall' that makes Iapetus look like a walnut. We can't think of an explanation. Hoagland thinks Iapetus is shaped like a 12-sided D&D dice - which it may well be given the evidence. It still doesn't make it that Iapetus is made by aliens as Hoagland claims, but all the same it begs the question, how did it get to be that shape if indeed it is a dodecahedron?
Seven In Row
My goodness, Kevin Brown didn't have to be any good as the Yankee bats exploded for 15 runs in their 15-6 win over the Oakland A's. It's a bit sad that the Yankees are chewing up on the slumping A's as I like them too and wanted to see them do well, only now the A's have stumbled into a losing streak of their own thanks, to running into the buzzsaw of the resurgent Yankees.
But heck, the Yankees are now 1 win away from .500. It's already 14 May; they'd better keep this up if they're going to catch the Orioles, the Red Sox and the Blue Jays.
- Art Neuro
No comments:
Post a Comment