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

( -- 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

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1.7 / 5 (15) Jul 18, 2008
I have watched the movie and was impressed initially until I noticed that the moon in the movie is orbitting the Earth in a geosynchronous orbit. Looks like a hoax to me.
4.3 / 5 (6) Jul 18, 2008
I've watched the movie, well, alot! And I can sort of see what you mean (that the moon seems to appear to move in unison with the Earth's rotation), but you have to remember we are seeing a very, very small arc of the moon's orbit, and just the small piece as it crosses in front of the Earth. You don't see the rest of the orbit and therefore don't have a good reference for comparing.
4.7 / 5 (9) Jul 18, 2008
It's not geosynchronous. It does not even appear so. Not even on casual viewing. On any given day the Moon is in the sky for nearly nine hours. I believe you will find that this "time-in-sight" matches with the video.

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.
2.7 / 5 (3) Jul 19, 2008
the thing is that it's just not as easy to determine if it's an earth-like planet from what we can observe. the planet can have several moons and the moons can travel at different orbits and so on...
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...
3.7 / 5 (7) Jul 19, 2008
I hope someone can help me understand. I have an inexpensive camera with a 500 mm lens that records 10mp camera raw files. There is an even smaller one out that records 14.75 mp. The major consumer camera makers are launching 24mp cameras. And Hasselblad just announced a 50mp camera. I have a very inexpensive and small telescope(it's 10 years old) that can show you the icecaps of Mars from my backyard. Why do so many NASA images look like they were taken with decades old optics? These probes fly through space for months, if not years, so I will simply not accept that download time is the issue.

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?
4.8 / 5 (5) Jul 19, 2008
The optics and hardware are often several years out of date! For Deep Impact, the spacecraft was built ~2000-2003 (although the design was a bit earlier), so the tech from back then is different from the tech today. There is no way for us to upgrade the camera on board now -- how would we get new cameras on board? And the prime Deep Impact mission was pretty short: from construction start to end of mission was less than a decade. Other missions last much longer with design and construction many years, sometimes a decade before the interesting part of the mission occurs.
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.
5 / 5 (4) Jul 19, 2008
The dismissive "pretty pictures" comment made me chuckle.

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.
4.3 / 5 (4) Jul 19, 2008
Yes, it will take more than slick posters. But how much does a block-buster movie cost? How much is this project?
5 / 5 (3) Jul 19, 2008
Also the environmental initiative has the advantage where people can see how it affects them in the short and long term. Few people see/understand the benefits of space exploration. And sometimes our very efforts at PR backfire because while you and I see the Big Picture, others see, well a pretty picture and why did we spend the millions on it? Just as there was an environmental crisis to spur the interest, it will likely take some cosmic crisis to goad people into action. But right now, it is still too abstract.
5 / 5 (4) Jul 19, 2008
Good answers to Mayday's questions! It's great to see PhysOrg comments nail an issue so comprehensively!

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 the math.
5 / 5 (4) Jul 19, 2008
Yes, excellent responses, thanks.

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.
4.5 / 5 (4) Jul 19, 2008
The two biggest reasons why the hardware on spacecraft is so "out of date":

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.
3.3 / 5 (4) Jul 19, 2008
But back to the article and the film for a moment.

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?
3.7 / 5 (3) Jul 19, 2008
I thought the stills were fake at first because of the lack of parallax. Considering the camera is 31000000 miles away, I guess there wouldn't be any (confirmed with CAD). Seeing the earth still 4 times larger than the moon despite being another 250,000 miles further away threw me.
4.3 / 5 (4) Jul 20, 2008
If you ask Richard C Hoagland, The NASA images of mars are of the utmost quality- that is before some body scrubs them in the back room.
not rated yet Jul 20, 2008
Here's the world wide telescope developed by Microsoft. It's great:
1.5 / 5 (2) Jul 20, 2008
If you ask Richard C Hoagland, The NASA images of mars are of the utmost quality- that is before some body scrubs them in the back room.

And we have a very good idea why they are scrubbed......e.g. pre-airbrushed shots of the moon from the Rissians.
5 / 5 (5) Jul 20, 2008
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.

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.
4 / 5 (3) Jul 20, 2008
Oh, and as far as high quality images of Mars go, try the MRO HiRISE images:

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.
4.3 / 5 (3) Jul 20, 2008
how fast is this spacecraft moving while trying to film something 31million miles away? so what if the picture is slightly blury.

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