An Alien’s-Eye View of Earth

By Corey S. Powell | July 25, 2013 11:08 pm

Earlier this week, the visionaries who operate NASA’s Cassini spacecraft released a remarkable snapshot of Earth as seen from Saturn. It got a ton of media attention, and rightly so. It is a stunning celestial view that no human being can see first-hand, but that billions of people around the world can now experience vicariously. It starkly illustrates how small we are within the universe, while simultaneously celebrating the grand things our little species is capable of. I went on cable news to talk about it, and DISCOVER blogger Tom Yulsman wrote a poignant post about it.

But that new Cassini image is far from the only perspective-busting picture that has come in from humanity’s space fleet. In fact, there is a whole portfolio, many of them rarely seen. Collectively they offer what I call an alien’s-eye view of Earth: They show what our planet might look like to extraterrestrial scientist scoping out our planet from afar. Here I’ve pulled together a few of my favorites. [To follow me on Twitter: @coreyspowell]

Earthset on the moon. The Apollo astronauts captured shots of Earth rising on the moon, but this is the only full sequence I know of that shows Earth setting. (Both events occur only from orbit around the moon or from some other mobile vantage. For a stationary observer on the lunar surface, Earth hangs nearly motionless in the sky.) In 2007 Japan’s Kaguya spacecraft–also known as Selene–took both still images and HD video of Earth ominously vanishing from view. Earth’s south pole is facing up; Australia is at upper left on the globe but turned upside-down because of the orientation. The whole sequence covers about 70 seconds. (Credit: JAXA/NHK)






Solar eclipse from space. A solar eclipse happens when the moon passes in front of the sun…from Earth’s perspective. From the moon’s perspective, seen here, the moon’s shadow sweeps across the face of the Earth, giving our planet something of a black eye. The whole process lasts just a few hours and is difficult to capture, but NASA’s Lunar Reconnaissance Orbiter managed the feat on May 20, 2012. The center of the moon’s shadow lies off the coast of Alaska in this annotated image. The shadow itself looks gray and soft because the moon was too far away at the time to completely cover the sun, so some sunlight leaked into the darkened area. (Credit: NASA/GSFC/Arizona State University)

Eclipse from space











Crescent Earth: daylight and night lights. There are at least three very cool things going on in this image. First, it shows Earth as a slender crescent, highlighting the thin layer of atmosphere and the blue of the ocean that mark ours as a habitable planet. Second, the image also picks up a key trait that marks Earth as an inhabited planet: the lights of cities at night. Look carefully and you can see a bright line that marks the location of the Nile valley. (Capturing both sunlight and artificial light required a double exposure, with the two snaps taken 20 minutes apart.) Third, this view comes from the European Space Agency’s Rosetta spacecraft, which used Earth’s gravity to steer it toward Comet Churyumov–Gerasimenko. In November, 2014, if all goes well Rosetta will deploy a lander and make the most detailed study ever of a comet. (Credit: ESA/MPS/OSIRIS)

Earth by Night











Earth and the moon from below. Our quaint notions of up and down mean nothing in space, as illustrated by this family portrait taken by the NEAR spacecraft in 1998 while it was en route to the near-Earth asteroid Eros. From a distance of 400,000 kilometers, the camera is looking up (or is it down?) at Earth’s south pole, offering a view unavailable from any planet or moon in the solar system. Antarctica sits right in the middle. A video of the flyby makes the geometry much clearer. Sharp-eyed readers will notice that this picture has been doctored for dramatic effect: The moon has been brightened by a factor of 5 (in reality it is as gray as asphalt), and the distance between Earth and moon has been greatly cropped. That explains why the shadows of the two do not line up properly. (Credit: JHU/APL)

Earth and moon from NEAR









The solar system, inside out. The same day that the Cassini spacecraft was peering inward toward Earth from Saturn, the MESSENGER spacecraft was gazing outward from Mercury. Saturn has beautiful rings; Mercury looks a lot like the moon and has a terrible PR problem. So while everyone was celebrating the Saturn image, this similarly fascinating shot got little attention. Well, here it is in all its glory. Like many extreme perspective shots, it doesn’t have its full impact until you parse exactly what you are looking at. The big frame (below left)  shows a panorama of the whole solar system laid out in the sky as seen from the world closest to the sun. Callouts identify the planets; the background frames also pick up a little bit of the Milky  Way in the sky. The inset (below right) zooms in on Earth and the moon. To an astronaut staring up into the airless night sky of Mercury, Earth would be a brilliant blue dot, outshining any star, while the moon would appear as a second-magnitude companion dot half a degree away.

All the hopes, dreams, fears, hates, and loves of the world cling to that single blip of light. It reminds me of Neil Armstrong’s impression when he looked up from the surface of the moon: “It suddenly struck me that that tiny pea, pretty and blue, was the Earth. I put up my thumb and shut one eye, and my thumb blotted out the planet Earth. I didn’t feel like a giant. I felt very, very small.” (Credit: NASA/JHUAPL/CIW).

Messenger Mosaic

Messenger Earth

  • coreyspowell

    I’m still waiting for the most beautiful view of Earth from anywhere in the solar system other than the moon: the cloudtops of Venus. From Venus, Earth would be directly overhead and blazingly blue at opposition; the moon would be a first-magnitude white star a little over half a degree away. Unfortunately, no Venus orbiting spacecraft has taken that shot…and of course, there’s no chance of getting it from the Venusian surface.

  • Michael W. Perry

    I’m most concerned about how our planet might be viewed from a star system within a few dozen light years of us. Could they spot our cozy little ocean-blue planet at just the right distance from a stable star? I’d hate to see millions of them show up, eager to shove us out of the way.

    • Ken Albertsen

      Maybe they’ll just shove this one, most harmful, species out of the way – and allow all the other species to get back to surviving like they did before Man came along to trash the place and decimate other species.

    • coreyspowell

      I suspect that any species capable of interstellar travel would have access to such enormous resources and technology that they would be beyond the point of needing to colonize our planet. Terraforming Mars or building cities in space strike me as easier engineering problems than transporting large numbers of individuals across many light years.

      • Michael W. Perry

        That assumes they’d need a large army to defeat us in open battle. Far easier would be a small and stealthy craft whose scientists would careful tailor a virus that’d kill off only us, leaving the rest of our marvelous little world for the colonists who’d arrive later. One might even be so carefully crafted that it’d spread in a dormant state for many years to ensure that even isolated populations get infected.

        And perhaps they’re less concerned about finding a place for large masses that simply spreading their species across the galaxy. For the latter, a colony a mere thousands would suffice to populate our world in a few thousand years.

        That’d particularly be likely if they had an equivalent of Charles Darwin in their own intellectual background. Darwin-like ideas place a most unhealthy emphasis on species survival. That’s why some our own scientists have already begun to talk of finding other homes in the galaxy for our species. We need only assume that their scientists are thinking like ours.

        Never forget. Pitiful as it is, species survival is the closest materialist science can get to offering us immortality. That’s why there’s sadness in H. G. Wells’s Time Machine when the traveler discovers a distant earth on which no trace of us remains.

        • coreyspowell

          You make an interesting point. One of the things that I find ridiculous about so much science fiction is the assumption that an alien species trying to colonize Earth would come in with guns blazing. More likely they’d do some equivalent of pest control. “The Screwfly Sollution,” a short story by James Tiptree, Jr, is a brilliant imagining of how the pest-control approach might work.

          But my argument is that any species capable of interstellar travel already must have access to tremendous energy and resources. If so, it seems hard to believe that such a species would need to colonize an inhabited planet, rather than terraforming an uninhabited one, building space colonies, etc.

          Furthermore, if Earthlike planets are common, the aliens would have many worlds to choose from. If Earthlike planets are rare, they would have to travel a very long distance to get here, making the local resource options even more attractive. Of course, we can barely understand other cultures on this planet, so who is to say what the motivations of another species would be like.

          • Michael W. Perry

            “Guns blazing” is a good point. Movie plots are often driven by the ‘wow’ of special effects. Many of the changes Peter Jackson made to Lord of the Rings were to lengthen the battle scenes.

            I’m not sure an abundance of energy and resources would be all that helpful in planet shaping. Suppose you had an earth-like planet with only one fault–it lies about 10 million miles to close to a sun for comfort. It’s too miserably hot, from equator to pole, for comfort. You want to turn that 120 degree F average temperature to something closer to 60.

            Energy isn’t the issue. Planets aren’t like cars. Finding a way to attach to a planet to pull or push it further out runs up against some nasty engineering problems, particularly stresses that would have to placed on the planet’s crust to make the move possible in even a thousand-year time frame.

            A bigger issue might be the distinction between habitability and life, particularly life intelligent enough to regard the planet as their own. There’s an assumption today that planets similar to earth will have life on them–an assumption for which we have no data pro or con.

            If there are numerous habitable planets but few that actually have life, creating a new home would be relatively easy. Simply seed a planet with an array of living creatures to make it more livable and move in. Grass and trees to reduce erosion are an obvious choice, and animals would make living there more interesting. Chose the right plants and animals and you could also shape the climate to make it more pleasant.

  • Pictures jigsaw puzzles

    many useful information for me..This page is very informative


Out There

Notes from the far edge of space, astronomy, and physics.

About Corey S. Powell

Corey S. Powell is DISCOVER's Editor at Large and former Editor in Chief. Previously he has sat on the board of editors of Scientific American, taught science journalism at NYU, and been fired from NASA. Corey is the author of "20 Ways the World Could End," one of the first doomsday manuals, and "God in the Equation," an examination of the spiritual impulse in modern cosmology. He lives in Brooklyn, under nearly starless skies.


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