Much of Earth’s surface was covered by clouds, however, and what’s visible is dominated by Africa. A viewer’s eye is naturally drawn to the landmass; the same holds for updated Blue Marble images produced by NASA in 2001 and 2002, which center on North America and the Asian subcontinent.

But with three-quarters of Earth’s surface covered by water — arguably the most important ingredient for life, and certainly the host of most life on Earth — it’s not land on which a planetary photographer should focus. It’s water. And so it is with this new NASA image, in which land is just barely visible as a fringe of the Pacific Ocean.

In addition to restoring a certain geoscientific perspective, the photograph complements the original Blue Marble in another way. That image helped catalyzed an emerging environmental awareness, one conscious of both Earth’s beauty and humanity’s role as planetary steward. Nearly four decades later, our power to alter the environment is considered so profound as to define a new geological age, and even water is not exempt.

“The big questions for me are the effects of current climate changes on the water cycle. What’s suggested is that the water cycle might speed up,” said climatologist Claire Parkinson, lead scientist on NASA’s Aqua Project.

As temperatures rise, more water will evaporate, hastening its turnover in the atmosphere. On average, it now takes about nine days for an evaporated water molecule to come come back down. In the future, “it might take eight days, or seven,” said Parkinson. The water cycle could neatly fit a human week.

Image: NASA

See Also:

• Comet Hunter’s Last Look at Earth Is Haunting
• NASA’s Best Photos: You Make the Call
• Maps: How Mankind Remade Nature
• The ’70s Photos That Made Us Want to Save Earth
• 7 Tipping Points That Could Transform Earth

Brandon Keim’s Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on an ecological tipping point project.

Authors: Brandon Keim

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