Moon and Jupiter
Two worlds that've taken a pounding huddle close together this evening. The planet Jupiter looks like a brilliant star near the Moon as darkness falls. They remain close together as they sail across the southern sky before setting in the wee hours of the morning.
The Moon's pounding is pretty obvious. The Moon's covered with impact craters -- the result of collisions with rocky debris. The dark volcanic plains were formed by impacts, too -- giant impacts that punched holes in the lunar crust, allowing molten rock to bubble to the surface.
Jupiter has taken a pounding, too, but it's not obvious. That's because the planet is enveloped in a thick atmosphere. There's no solid surface to maintain the scars of its cosmic collisions.
When Jupiter gets hit, though, the scars can last for weeks or even months. An example is an impact that took place back in July. A comet or asteroid the size of a few city blocks slammed into Jupiter's southern hemisphere. The impact created a dark stain that within hours was as wide as Earth. Over time, though, the Jovian winds disperse the stain, so there won't be a permanent record of the impact.
There's little doubt that Jupiter gets hit a lot, though. It's the biggest planet in the solar system, and has the strongest gravity. So it's certain that Jupiter has pulled in countless chunks of debris over the eons -- debris that's pounded the giant planet, without leaving any scars.
Script by Damond Benningfield, Copyright 2009
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
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