Earth In High-Definition and Living Color

Space photographs of the full globe of Earth taken by the Apollo astronauts in the late 1960s first revealed just how fragile and finite a world we live upon.

The Earth was dubbed the "blue marble" floating against an inky background of infinite depth. Those photos are credited with inspiring the birth of Earth Day 40 years ago, and launching the environmental movement.

NASA's Goddard Space Flight Center has posted pictures of what it describes as the best-ever photos of Earth, on a project called "Blue Marble Next Generation." The globe is assembled from a mosaic of satellite data taken mostly from a sensor called the Moderate Resolution Imaging Spectroradiometer (MODIS) that flies aboard NASA's Terra and Aqua satellites. Details as small as 1600 feet across can be seen. The catalog is available at NASA's Visible Earth.

The Next Generation version offers a year's worth of monthly composite images that reveal seasonal rhythm of mother Earth: the spring greening and fall browning of vegetation in temperate regions, dry and wet seasons in the tropics, and the advancing and retreating Northern Hemisphere snow cover. When combined into a time-lapse movie the dataset is reminiscent of "time machine" views of reality, as animated in two film versions (1960 and 2002) of H.G. Wells’ classic, The Time Machine.

Regrettably most of the world’s population is jaded today with seeing yet another picture of Earth. It's even the default wallpaper on Apple's iPhone. And, all I have to do is turn my Dish Network TV satellite feed to "Earth channel" and get a live view of our planet from geosynchronous orbit 24/7.

Nevertheless the new pictures are spellbinding. "The Lord makes some beautiful worlds," exclaimed a starship navigator in the 1956 film classic Forbidden Planet.

The refined pictures leave you breathless if not a little plaintive. With all the concern today about climate change, species extinction, and deforestation you worry how much this little terrestrial planet can take with the exploding population of Homo sapiens.

There must be many millions of "blue marble" planets scattered across our Milky Way galaxy. I wonder how their continents look different from ours. That is, for those worlds with floating continental crust. A large number should simply be purely water worlds weighing in at several times Earth's mass.

All we can do today is detect the shadows of such worlds when they orbit in front of their star. NASA's Kepler observatory is dutifully assembling a database that will give us the statistical abundance of Earth-like planets in their star's habitable zone.

But what they really look like will be left to our imagination for a very long time.

If Kepler shows that Earth-like worlds are common, scientists will be motivated to build a flotilla of 8-meter telescopes, flying in formation at separations twice the diameter of the moon, to photomap nearby Earth analogs. Though incredibly technologically challenging and expensive, I expect that this will be accomplished before the year 2100.

If we eventually capture an image of another blue marble in space, it will immediately become the Picture of the Century. It will solidify the notion that we are not alone in the universe. It will be like coming face-to-face with another inhabitant on a vast desert island.