Best Science Photos of the Week - April 28, 2012

A new estimate of the number of habitable planets orbiting the most common type of stars, called red dwarfs, in our galaxy could have huge consequences for the search for life. Shown here, an artist's impression of sunrise from the surface of Gliese 581c, an Earthlike planet in the habitable zone of its red dwarf star. [Read full story]
Space shuttle Enterprise, the prototype for NASA's storied orbiter fleet, is now a New Yorker. The original test space shuttle, Enterprise flew into the Big Apple on Friday (April 27) atop a modified Boeing 747 jumbo jet. [Read full story]
As many as 90 percent of reef sharks have disappeared from reefs near populated islands, a new study finds. Shown here, gray reef sharks (Carcharhinus amlyrhynchos) at Kure Atoll in the Papahanaumokuakea Marine National Monument, Hawaii. [Read full story]
A new international campaign hopes to save a group of people who have been dubbed "the most threatened tribe in the world" — the Awá tribe of Brazil — from encroaching outsiders who are gobbling up their land. [Read full story]
A tribal girl nicknamed "Little Butterfly" bathes in a stream near her community. [See more photos of the threatened tribe]
A mature all-white male orca, the only one of its kind known, has been spotted in the North Pacific off the east coast of Russia, scientists announced Monday (April 23). After seeing its towering white dorsal fin breaking through the water's surface, the team named the distinctive beast "Iceberg." [Read full story]
A minivan-sized meteoroid dives through the atmosphere, leaving a trail of fire visible across Nevada and California. The space rock rattled windows over California's Central Valley at about 8 a.m. PT on Sunday, April 22 when it exploded in the upper atmosphere, releasing energy equivalent to a 5-kiloton burst. NASA experts estimate that the object weighed about 154,300 pounds (70 metric tons).
In the western San Bernardino Mountains, near the highway that links Los Angeles and Las Vegas, scientists recently discovered a geological mystery: colossal rocks perched in precarious poses right next door to the San Andreas Fault. What's most perplexing is that the rocks seem to be immune to the powerful shaking of nearby earthquakes. [Read full story]
Four new species of crab that sport some wild colors have been discovered near the Philippine island of Palawan. Shown here, one of the newly discovered crab species, Insulamon palawanense, which is bright purple in color. [Read full story]
Named for their mother-of-pearl iridescence, nacreous clouds blanket the sky above Husavik, Iceland in December 2011, and posted this week in our Image of the Day album. These clouds, also known as polar stratospheric clouds, occur high in the atmosphere, 49,000 to 82,000 feet (15,000 to 25,000 meters) up. Thanks to their high altitude, the clouds reflect light from the setting or rising sun before it breaches the horizon, causing their ethereal glow.
A newly discovered skeleton from an ancient three-toed horse not only provides information about ancient Tibetan wildlife, but it also sheds light on the habitat and elevation of Tibet nearly 5 million years ago. Shown here, exposures of sediments in the Zanda Basin where the skeleton of the Zanda horse was excavated. [Read full story]
