Strangers in a strange solar system

After a while you get the feeling the solar system is a pretty strange place. Not only from looking at otherworldly pictures of moons and planets sent from spacecraft, but also because scientists say so.

At least a half-dozen objects, probably more, have been described as “the strangest place in the solar system” by some awestruck authority. I imagine Jupiter’s moon Io might get the most overall hits on the word “strangest.” It warps, buckles, seethes and erupts like no other known place. Uranus’ moon Miranda might run second – it’s small and round but it’s weirdly jagged, with sheer cliffs miles deep.

There’s also Saturn’s moon Titan, which is covered in a heavy orange smog (and, apparently, lakes) of hydrocarbons that might nourish life. And Neptune’s moon Triton, which is probably the coldest place of all (minus 390 degrees Fahrenheit, colder than Pluto, or hell) but nonetheless has a thin nitrogen-methane atmosphere, spews ice, and revolves around Neptune backward. Also strange is Jupiter’s moon Europa, which is covered by a frozen ocean.

Some of Saturn’s other moons get called strange too. Hyperion, which looks almost exactly like a russet potato, is the largest irregularly shaped object in the solar system. Enceladus is nearly pure white, the brightest nonsun object known, and shoots out water ice.

Then there’s Iapetus. It’s less than half the size of our moon. (Nothing strange there – most moons are smaller than ours.) But last year the Cassini spacecraft sent close-up photos of its surface that looked even stranger than it did through telescopes in the 1960s, when it already seemed so uncanny that Arthur C. Clarke portrayed it as a stargate to other dimensions in the novel “2001.” Iapetus is half dark and half light – literally. In its orbit around Saturn, which takes about 79 Earth days, its leading half is practically black, and its trailing half is very bright, practically white.

Now, some astronomers say this is the strangest thing in the solar system. No other object is neatly divided half and half of anything. What’s weirder still is that almost exactly along the middle of Iapetus, where the dark divides from the light, is a mountain range, in places 8 miles high. It resembles the ridge around a walnut shell. No other known moon has a mountain range exactly tracing its equator.

The bright half of Iapetus is covered by ice. The photos show what looks like snow fields over small and huge craters. The dark half, which seems black but is generally a very dark reddish color, is thought to be made of organic materials. No one knows how it got like this. Black splatters on the dividing line led to the theory that material from another Saturnian moon, possibly Hyperion or Phoebe, somehow inundated Iapetus’ leading half and coated it black.

I don’t know if this is as strange as Io’s horrible, belching sulfur volcanoes and seething yellow surface. But no one can say, really. “Strange” is not a scientific word (except for one specialized use in subatomic physics, where it does not mean strange at all), even though astronomers use it all the time. “Strange” means different or unfamiliar in a way that causes uneasiness and allure. “Strange” is a feeling you get, not an objective physical condition.

When you think about it, the place most different from everything else in the solar system is not Io or Iapetus, but the Earth, with its blue oceans and greenery and living beings. To us, it’s familiar. In other places, we’re the strangers, with strange words to describe what in our hearts feels very strange. It’s a strange universe.

Dana Wilde may be reached at dwilde@bangordailynews.net. More Amateur Naturalist observations are available at www.bangornews.com and www.dwildepress.net/naturalist.