|  |  N. Korea tested rocket engine: think-tank
 North Korea tested a rocket engine earlier this year in a potential bid to further develop its missile capability, a US think-tank said Thursday after reviewing new satellite images.  ... more
 
 |  |  Gaps in dust around stars may not indicate planets as many believe
 Gaps in dusty disks around young stars, thought by many astronomers to be indicative of planet formation, can occur without planets, U.S. scientists say.  ... more
 
 |  |  Surveys reveal ancient impact crater beneath Iowa town
 Scientists say air and ground surveys have allowed them to confirm the existence of an ancient impact crater buried beneath a town in Iowa.  ... more
 
 |  |  Most accurate atomic clock ever built could redefine the second
 European scientists say they have found a more accurate way to measure time, with a new type of atomic clock termed the most accurate yet devised.  ... more
 
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