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Year in ReviewFrom the detection of potentially habitable alien planets, to the discovery of a new moon around Pluto and jaw-dropping eclipses, astronomical research in 2011 made extraordinary strides and raised tantalizing questions for the future.
Here's a look at the 11 best astronomy stories of 2011:
Ongoing Search for Alien LifeSlide 2 of 24
Ongoing Search for Alien LifeIn early March, a study published in the Journal of Cosmology ignited a controversy over the possible detection of alien life in meteorites.
Astrobiologist Richard Hoover of NASA's Marshall Space Flight Center in Huntsvilla, Ala., used scanning electron microscopes to analyze slices of carbonaceous meteorites that fell to Earth from space. In his study, Hoover claimed to have detected "filaments" and other features that resemble microbes in the meteorites. [5 Bold Claims of Alien Life]
The study was quickly criticized by other scientists, who discredited the research and said that the findings did not amount to convincing evidence.
In a less controversial announcement on Dec. 7, scientists presented findings from the Mars rover, Opportunity, that amounted to the best evidence yet that water flowed on the planet long ago. Opportunity discovered a thin, bright mineral vein along the rim of the huge Endeavour crater. According to scientists, the mineral is almost certainly gypsum that was deposited by liquid water billions of years ago.
NASA launched its newest mission, the Mars Science Laboratory (MSL), to the Red Planet Nov. 26. When the car-size rover Curiosity touches down on Mars in August, it will likely help researchers gain a better understanding of the planet and its environment.Slide 3 of 24
Gains Made in Search for Killer Space RocksSlide 4 of 24
Gains Made in Search for Killer Space RocksIn September, a NASA study was released that found fewer potentially dangerous asteroids orbiting Earth than was previously thought. The discovery significantly lowered the number of medium-size asteroids near Earth to 19,500, which represented nearly a 50-percent drop from initial estimates.
The study's findings suggested that the threat to Earth by dangerous asteroids may also be somewhat less than previously thought. But scientists also said thousands more of these asteroids remain to be found. [Photos: Asteroids in Deep Space]Slide 5 of 24
Asteroids, Oh My!Slide 6 of 24
Asteroids, Oh My!After launching in 2007, NASA's Dawn spacecraft arrived at the asteroid Vesta in July to kick off a yearlong study of the giant space rock. Since its arrival, Dawn has already beamed back some of the clearest views yet of the huge, battered asteroid, including images of massive depressions and a huge mountain inside an expansive crater.
Vesta is the second-most-massive object in the main asteroid belt between Mars and Jupiter. After spending a year at Vesta, Dawn will travel to the asteroid Ceres, which is the largest body in the main asteroid belt. [Photos: Asteroid Vesta and NASA's Dawn Spacecraft]
But Vesta wasn't the only asteroid to make headlines in 2011.
An asteroid the size of a city block, called 2005 YU55, zipped past Earth in a rare flyby that marked the closest such a large asteroid has come to our planet in 35 years. The space rock passed within the orbit of the moon Nov. 8 before speeding off into deep space.
The asteroid was never in danger of hitting Earth, but it did provide researchers with an unprecedented opportunity to learn more about 2005 YU55 and its orbit. [5 Reasons to Care About Asteroids]Slide 7 of 24
Fantastic Lunar and Solar EclipsesSlide 8 of 24