Deep Impact Films Earth as an Alien World
July 18, 2008
Series of images showing the Moon transiting Earth, captured by NASA's EPOXI spacecraft. Credit: Donald J. Lindler, Sigma Space Corporation/GSFC; EPOCh/DIXI Science Teams
(PhysOrg.com) -- NASA's Deep Impact spacecraft has created a video of the moon transiting (passing in front of) Earth as seen from the spacecraft's point of view 31 million miles away. Scientists are using the video to develop techniques to study alien worlds.
"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, Earth-like alien world would appear to us," said University of Maryland astronomer Michael A’Hearn, principal investigator for the Deep Impact extended mission, called EPOXI.
Deep Impact made history when the mission team directed an impactor from the spacecraft into comet Tempel 1 on July 4, 2005. NASA recently extended the mission, redirecting the spacecraft for a flyby of comet Hartley 2 on Nov. 4, 2010.
EPOXI is a combination of the names for the two extended mission components: a search for alien (extrasolar) planets during the cruise to Hartley 2, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact eXtended Investigation (DIXI).
During a full Earth rotation, images obtained by Deep Impact at a 15-minute cadence have been combined to make a color video. During the video, the moon enters the frame (because of its orbital motion) and transits Earth, then leaves the frame. Other spacecraft have imaged Earth and the moon from space, but 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.
"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, Cambridge, Mass., and a co-investigator on EPOXI. "Nevertheless, planet-characterizing space telescopes under study by NASA would be able to observe an Earth twin as a single point of light -- a point whose total brightness changes with time as different land masses and oceans rotate in and out of view. The video will help us connect a varying point of planetary light with underlying oceans, continents, and clouds -- and finding oceans on extrasolar planets means identifying potentially habitable worlds." said Seager.
"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. Deming is deputy principal investigator for EPOXI, and leads the EPOCh observations. "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. Also, we used infrared light instead of the normal red light to make the color composite images, and that makes the land masses much more visible."
That happens because plants reflect more strongly in the near-infrared, Deming explained. Hence the video illustrates the potential for detecting vegetated land masses on extrasolar planets by looking for variations in the intensity of their near-infrared light as the planet rotates.
Provided by NASA
Oct 07, 2009 |
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If your comment was an attempt at irony, keep your day job. If it was, though unbelievable to me personally, serious... Sceptical1 is advised, with all due respect, to get a life.
i really doubt that with current technology we can _detect_ earth-size planets, despite of determining if there are some kind of earth-like features .... and this simulation is not going to help...
After waiting anxiously, as we did, the optical quality of the comet impact images from Deep Imact were so low as to be startling!
What gives?
I love this assembled movie of the Earth and Moon. But more people might support the NASA mission if they would make the effort to produce some quality PR material for themselves.
This movie is spectacular in so many respects, but given today's available optical quality, it is almost touchingly sad.
How can we convince NASA that it might be worth their while to procure quality imaging systems?
And yes download times are a factor. We don't exactly have a t1 line connecting us to the spacecraft. It's more like the old dialup modem connections!
However for these images, there are two key points at play:
1) The HRI camera used to take the images is ever so slightly out of focus, so the images must be deconvoluted. While not good for getting "pretty" pictures, this makes it ideal for doing photometry and hence one of the reasons the whole transiting exoplanet project was selected.
2) The spacecraft was 31 million miles away! That's 1/3 AU. We are seeing a cropped piece of the original frame. The HRI is a 30cm f/35 system (http://deepimpact...s.html).
You should one take a walk through the halls of some of the big professional observatories where they have some of their pictures hung up... taken with some of the big (meter ) professional telescopes back in the 60-80's, they look pretty primitive compared to the images being taken by amateurs today. You have to be careful about comparing apples to oranges.
As a final note, I'm not sure what you mean by "quality PR material," but funding for a mission is mostly for the science, with a wee bit for outreach, which I guess would include "PR" but that doesn't mean that we have funds to make slick posters and stuff. In order to get this movie, the project went outside to another scientist, who was familiar with the project but not on it and who is an expert on deconvolution, to help process the frames. He wasn't in the original budget, so something else got sacrificed I'm sure.
Here is the rub. For NASA to succeed at procuring a continued stream of funding from Congress, it will need to do a better job at garnering public support. The science is wonderful, well thought through and generally impeccibly executed. The knowledge gains are great, even on a shoestring. But without a backstop of public support and belief behind the Congressman/woman who would rather pork-barrel their favorite cronies back home, the future of NASA funding does not look bright.
You seem closely involved. And please, I am a fan of space science. But it pains me to see public support for NASA continue to wane. And to see NASA doing so little to help the public develop some enthusiasm for the greater mission. On the corporate side, there is a "science" to developing enthusiasm as well. And it is very well developed. That is the PR reference I made.
In a funding system that requires the support of highly distracted elected officials in order to get your dinner, that "wee bit for outreach" simply isn't doing the job today.
I'd suggest that like most successful corporate initiatives, NASA should begin to consider successful outreach(to use your term) as a mission-critical component(NASA's mission, not the myopic view of "this craft's" mission) of every spacecraft design.
I am a supporter offering what I hope is helpful advice.
And I'm afraid it's going to take more than "slick posters." Today's wildly popular environmental initiative is driven by Oscar-winning feature films, star power and massive grassroots PR efforts. You see, it works.
Hee, hee. I'm going to quibble with AdAstraGRL, though. (In no way invalidating her answers overall to Mayday.) 1) A blockbuster movie usually *makes* money. I.e., it pays for itself. How many astronomical photos do that? 2) While it's true that a cosmic crisis would goad people into action, the chances of that happening in the next 50 years -- compared to chances of the extinction of 1,000s of species in the next 50 years due to pollution...well...do the math.
My suggestion would be to develop a many pronged grassroots effort to first, find your best supporters(we're out here), and second to develop the supporters who can initiate the next turn of the snowball -- authors, screenplay writers, columnists, computer game developers, toy designers, comic book developers(don't laugh, it's big biz) -- to know the potential role they can play and to begin to take part in advancing the mission.
Then, bring your true fans inside. Let these people who can help have access to the things that they can use to help you. Let them see and touch the technology. I find the actual physical equipment used to explore space to be full of emotional portent when seen up-close. But there is very little public access to the stuff.
This kind of effort would take very modest funding -- and some dedicated team members willing to donate time.
Next would be to find or develop friends in Hollywood, with TV content producers and media thought leaders(yeah, like Oprah). Invite them inside as well. Give a few(once you are sure that they are in fact friends) a total back-stage full-access pass to a major mission. Let them tell the story from their unique and trusted perspective. Let it be emotional.
You have a good story. Find your friends and let them tell it. This truth, well told, can and will move people.
1) They were built years ago, and designed years before that. By the time we see pics like these the hardware is a decade old, or even more in the case of something like Casini.
2) The hardware has to be radiation hardened to survive in space that long. It takes many years for "current" hardware to be re-engineered to withstand high doses of radiation. As an example, try taking a brand new laptop on a trans-Atlantic flight. It'll reboot constantly because of the increased high energy particle radiation at those altitudes (2 or 3 times during the flight, usually). And that isn't even dangerous amounts of radiation yet. So add a good 5 extra years onto the age of the hardware, prior to the date of final hardware selection during the building of the spacecraft.
I find it interesting how the Moon appears so much darker than the Earth. And that the shadow edge(I've forgotten the technical term) seems so soft and ill defined. Compare this to looking up at night(not tonite, too full of a disc). The shadow edge is quite starkly defined, no matter how you squint, and the Moon appears quite bright and strictly colorless. Even in broad daylight the moon appears as a bright white-ish orb.
I even reviewed some old Apollo photography. Only rarely does the lunar surface take on any color. Most notable in "Earthrise" where it does wax a warmish gray, near brown. I only see this there and here, in this video.
Even against mighty Jupiter the teenie moons pop out bright. Here we see a dull brown ball with an edge softer than our own atmosphere-smeared shadow.
I'm not trying to call fake, as some early posters were(The off-hand "simulation" remark was funny, though). I was just wondering what it is that I'm perceiving.
Perhaps if we could see the unprocessed frames?
http://www.worldw...exp=true
And we have a very good idea why they are scrubbed......e.g. pre-airbrushed shots of the moon from the Rissians.
There's a relatively straight forward explanation for this.
The Earth has an average albedo of 0.367, the moon has an average albedo of 0.12
The moon appears dark in the images because it's against the backdrop of the earth, which is three times brighter.
It's comparable to the thing they say about sunspots - they might appear black against the surface of the sun, but they'd glow white hot on their own in space.
It's the same with the moon, it appears dark against the earth, because the earth is 3 times brighter, but from earth, in the night sky, it appears bright, because it's the brightest object in the sky.
http://hirise.lpl.arizona.edu/
The MRO HiRISE camera has been able to capture other vehicles on the surface of mars, including most recently the Phoenix lander - which it also managed to capture during its descent.
http://hirise.lpl.arizona.edu/phoenix.php