Friday, July 18, 2008

One really cool movie

Credit: D. Linder / EPOXI / NASA

The video above shows a very unique view of the Earth/moon system. It was taken by the EPOXI Mission, the name of NASA's Deep Impact spacecraft's new mission (now that it's completed its mission to explore Comet Tempel 1). The spacecraft turned its onboard camera toward the Earth in late May when it was 31 million miles away from Earth, and it captured (intentionally) the Moon passing in front of the Earth.

The video above is roughly true color. A cartoon globe in the lower left shows you what parts of the Earth are visible at any given time. If you look closely toward the center right of the Earth, you can see "sunglint," the reflection of sunlight off of the oceans in the direction of the spacecraft.

Notice the color difference between the Earth and the moon. The moon looks dark and reddish. That's the true color of the moon. It looks bright and silvery in our sky, but if we had another bright Earth near the moon in our sky, we'd see how reddish and dark the moon really is.

Also notice the relative size of the Earth and the moon (also correct); it can give you some idea of how small the moon is. The only thing this picture doesn't do is give you an idea of the relative separation of the Earth and moon; the moon is roughly 30 Earth-diameters closer to the spacecraft than the Earth is.

Another version of the video shows the same scene, but it includes some infrared imaging, which brings out vegetation (plants reflect a lot of infrared light). In this version, you can see parts of the continents even better. NASA's Landsat satellites use the same infrared colors to track changes in plant life on Earth, such as these pictures showing the damage caused by illegal logging in Indonesia over a 10 year period.

I find views of the Earth like this are very helpful in reminding myself of our place in the Universe, and how small and unique that place is. Some other views of our planet from outer space:

Special thanks to Phil Plait for posting the EPOXI videos on YouTube and for bringing my attention to them.

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