The eastern Grand Canyon was about half-carved (to the level of the red cliffs above the hiker) from 15 million to 25 million years ago, an analysis published Sunday suggests. But the inner gorge was likely scooped out by the Colorado River in just the past 6 million years.
Laura Crossey/University of New Mexico
Computer networks and GPS systems are only possible because of the precision timekeeping of atomic clocks like the one above, says clockmaker and physicist Jun Ye.
Ye Group and Baxley/JILA
Kepler-22b, seen in this artist's rendering, is a planet a bit larger than Earth that orbits in the habitable zone of its star. Some researchers think there might be "superhabitable" worlds that may not resemble Earth.
The plate on the left contains about equal numbers of colonies of two different bacteria. After the bacteria compete and evolve, the lighter ones have taken the lead in the plate on the right.
Courtesy of Michael Wiser
This is an artist's illustration of Kepler-62f, a planet in the "habitable zone" of a star that is slightly smaller and cooler than ours. Kepler-62f is roughly 40 percent larger than Earth.