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Moon and Jupiter

January 21, 2013

Two worlds that have taken a beating stage a spectacular encounter in tonight’s sky. The Moon will swing quite close to the planet Jupiter, which shines like a brilliant star.

The Moon’s most prominent features are its impact basins. They formed billions of years ago, when giant asteroids slammed into the Moon. The basins filled with molten rock, forming the dark volcanic plains we see today.

Yet the Moon also carries the scars of much smaller impacts, which form craters. These have formed throughout the Moon’s lifetime.

You won’t find an impact crater anywhere on Jupiter, because the planet is a ball of gas, with no solid surface. But like the Moon, it continues to get hit. And its composition makes those impacts stand out — but only for a while.

The most spectacular impacts came almost two decades ago, when the remnants of a fractured comet hit Jupiter like a cosmic hailstorm. But the aftermath of several smaller impacts have been seen over the last few years.

When space rocks slam into Jupiter’s upper atmosphere, they explode. That stirs up material from below the planet’s cloud tops, forming dark splotches. Strong high-altitude winds sweep these blotches into long streaks that can last for days or weeks.

Jupiter is the largest planet in the solar system, and it has the strongest gravity, so it’s a big target for asteroids. They continually pound the planet — they just don’t leave long-lasting scars for us to see.


Script by Damond Benningfield, Copyright 2012

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