NASA's Deep Impact / EPOXI spacecraft creates video of Earth from 50 million km away / Nave Deep Impact Filma la Tierra como un Mundo Extra Terrestre

Saturday, July 19, 2008

Image:121520main HRI-Movie.gif
NASA's Deep Space 1 probe has been and continues to be a very useful probe. It's the probe that provided the image above of an impactor striking the surface of the comet 9P/Tempel, and after fulfilling its primary mission it was decided after a bit of aimless wandering around the Sun that it could be used in a secondary mission called EPOXI, where it would both aid in the search for extrasolar planets (since it has a huge amount of time to focus on distant stars), and then in 2010 will visit another comet called Hartley 2. These are always my favourite missions because all they cost are the salaries of a few extra people whereas sending up a new mission to do the same thing runs into the hundreds of millions of dollars. As Wikipedia puts it:

In addition to investigating comet Hartley 2, the spacecraft will point the larger of its two telescopes at nearby previously discovered extrasolar planetary systems in late January 2008. It will study the physical properties of giant planets and search for rings, moons and planets as small as three Earth masses. It also will look at Earth as though it were an extrasolar planet to provide data that could become the standard for characterizing these types of planets.

"The search for exosolar planetary systems is one of the most intriguing explorations of our time," said Drake Deming, Epoxi deputy principal investigator at NASA's Goddard Space Flight Center, Greenbelt, Md. "With Epoxi we have the potential to discover new worlds and even analyze the light they emit to perhaps discover what atmospheres they possess."

And that's what it did (the part up there in bold, that is). It's the Earth from 50 million km out (one third the distance from the Earth to the Sun) along with a transit of the Moon. With good enough telescopes in the future we may be able to directly image extrasolar planets in this way, and it's helpful to have these videos of the Earth to help us know exactly what we're looking for, in the same way it helps to leave a forest and look at it from the top of a mountain to get a real idea of how the whole area is made up. See the video by going to's article here. also has an article on the video, and has some information on exactly why this new video is helpful:

While other spacecraft, including Voyager 1 and Galileo, have imaged Earth and the moon from space, Deep Impact is the first to show a transit of Earth with enough detail to see large craters on the moon and oceans and continents on Earth.

"Our video shows some specific features that are important for observations of Earth-like planets orbiting other stars," said Drake Deming of NASA's Goddard Space Flight Center in Greenbelt, Md., and the deputy principal investigator for the extended mission. "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."

The team used infrared light to look at the Earth because plants reflect more strongly in the near-infrared, so the video will help scientists evaluate the potential for detecting vegetated land masses on alien planets.


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