What Makes Up the Moon

In 1992, the Jupiter-bound Galileo spacecraft made a pass by our planet’s closest companion, the moon. This mosaic of 53 images shows the different composition of rocks on the moon's surface. Blue and orange colors represent lava flows, bright pink areas are highlands, and light blue colors indicate recent impact material with the youngest craters showing blue rays extending away from them. Image: NASA/JPL

Before 1962, most of the planets in our solar system appeared as hardly more than blurry dots in some astronomer’s telescope.

The most that scientists knew about Mercury, Venus, or Jupiter was their size, surface temperature, and atmospheric composition. But on Dec. 14, 1962, the Mariner 2 spacecraft flew by Venus. For the first time, researchers had detailed and up-close information about another world, helping spawn new scientific fields such as astrogeology and modern planetary science. The planets in our solar system changed from distant points to fully fledged worlds, with distinctive and amazing features.

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