The crescent Moon looks down on the planet Mars this evening. They’re quite low in the southwest as darkness falls, and set not long afterwards. Mars looks like a modest orange star directly below the Moon.
Although the Moon and Mars are a long way off, we actually have pieces of them here on Earth. The main source of Moon samples is the Apollo missions of the 1960s and ‘70s; astronauts brought back more than 840 pounds of lunar rock and soil. In fact, the last of those samples, collected by the crew of Apollo 17, began the journey to Earth 40 years ago tomorrow.
But pieces of both the Moon and Mars actually made it to Earth on their own, as meteorites — rocks that traveled through space and fell to Earth.
These rocks were blasted into space when asteroids slammed into the surfaces of Mars or the Moon. The impacts threw debris clear of their parent worlds. Some of these pieces eventually found their way to Earth.
Most of the meteorites from Mars and the Moon have been found in Antarctica or in the deserts of Africa and the Middle East, where there are few Earth rocks to clutter things up.
Scientists determine where these rocks come from by carefully measuring traces of gas trapped in tiny bubbles in the rock. They compare these gases to measurements of the Apollo Moon rocks, or to measurements made on Mars by robotic landers. The mixtures of these gases are unique to Mars and the Moon — confirming their extraterrestrial origin.
Script by Damond Benningfield, Copyright 2012
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