Probe sends alien’s-eye view of Earth

A NASA spacecraft sent on a mission to inspect comets has filmed Earth and its moon from 31 million miles away, creating an alien’s-eye view of our world.

The two brief sequences show the moon passing in front of Earth as it orbits. The sequences were part of a test aimed at developing techniques for studying planets around distant suns.

“Making a video of Earth from so far away helps the search for other life-bearing planets in the universe by giving insights into how a distant, Earthlike alien world would appear to us,” University of Maryland astronomer Michael A’Hearn, who leads the project using NASA’s Deep Impact spacecraft, said Thursday in a NASA advisory.

Deep Impact made a splash in 2005 when it fired a high-tech impactor into Comet Tempel 1 during a flyby and studied the resulting debris.

Since then, scientists have devised two new missions for the probe. One mission is aimed at searching for alien worlds and is known as Extrasolar Planet Observations and Characterization, or EPOCh. The other mission involves a flyby of Comet Hartley 2 and is called the Deep Impact eXtended Investigation, or DIXI. The double-dip mission has been dubbed EPOXI.

The Deep Impact probe captured its images of the lunar transit in May, and scientists combined them into a time-lapse video.

“Our video shows some specific features that are important for observations of Earthlike planets orbiting other stars,” Drake Deming of NASA’s Goddard Space Flight Center said. “A ‘sun glint’ can be seen in the movie, caused by light reflected from Earth’s oceans, and similar glints to be observed from extrasolar planets could indicate alien oceans.”

Deming said one version of the color-composite video incorporates an infrared view instead of the visible-red view. Plants reflect more strongly in the infrared, and as a result Earth's land masses show up more vividly than they would otherwise, he said. A similar infrared-imaging technique could be used to observe extrasolar planets for signs of vegetation.

Although 31 million miles sounds like a long way, that is closer than Mars ever gets to Earth. In comparison, the nearest star beyond the sun, Proxima Centauri, is roughly 25 trillion miles away. Thus, it would be difficult to see an extrasolar planet as well as Deep Impact saw Earth.

“To image Earth in a similar fashion, an alien civilization would need technology far beyond what Earthlings can even dream of building,” said Sara Seager, a planetary theorist at the Massachusetts Institute of Technology.

The video and other images are available at NASA's Web site. This report includes information from Reuters and msnbc.com.

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