Wednesday, April 05, 2006

Cosmic Dust, and Other Saturnian Stuff

The Cassini spacecraft, currently in orbit around Saturn, is solving one of the oldest mysteries about Saturn’s rings.

It has long been believed that the rings are the result of collisions of various solar system objects. But one thing has puzzled scientists for years. If the rings are actually made of pieces of collided matter, there should be a wide variety of sizes of matter. Until recently, only dust-like particles have been observed.

Think of it this way: Drop your favorite piece of fine china on a marble floor. Go ahead, drop it.

Okay, just remember  the last time you dropped your favorite piece of fine china. What did you get? Two or three large pieces, a dozen or so smaller pieces, some small chips, and some pieces that were reduced to dust.

Physicists tell us that whenever matter separates or coalesces, it will form a few large pieces, several medium-size pieces, and millions of tiny pieces. And what happens in your kitchen happens on a cosmic scale as well.

Back to Saturn’s rings. If the rings were formed by a collision, where are the larger pieces? Last year, Cassini found a few small “moonlets” inside the gaps between the rings, right where the theory said they should have been.

And last week, it was announced that several medium particles were discovered plowing a path through the rings. Finally, all three sizes of particles have been observed. Physics once again was proven by superior engineering.

What happens on your kitchen floor and what happens in the sub-system of Saturn happens in the solar system at large, too. There are a couple of large planets — Jupiter and Saturn — several medium planets — Earth, Venus, Mars — and millions of tiny planetoids — asteroids, the Kupier belt and a bunch of other stuff whizzing around out there. We’ve even discovered a tenth planet outside the orbit of Pluto. And we’ve found a few other planet “candidates” around the orbit of Neptune.

And remember all the glass “dust” on your kitchen floor? The solar system is full of it. The weight of the Earth actually increases by thousands of tons every year as it accumulates dust in its orbit. You see this on dark nights as shooting stars.

So here we are on our medium-size planet, zipping through space, accumulating dust, surrounded by stuff of all sizes. The solar system used to be such a “neat” place; nine planets and few asteroids. We are now beginning to understand just how incredibly complex it is. Just like that fine china on our floor.

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