NASA Administrator Charles Bolden speaks at a panel discussion on the search for life beyond Earth at NASA headquarters in 2014. Joel Kowsky/NASA hide caption

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A NASA team has attached nearly all of the hexagonal segments that will together make the primary mirror for the James Webb Space Telescope (pictured are practice segments). Chris Gunn/NASA hide caption

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2015 was the warmest year on record — and by the widest margin ever, according to a new analysis by NASA and NOAA. Scientific Visualization Studio/Goddard Space Flight Center hide caption

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The inset image shows X-ray arcs that astronomers say are signs of galactic burping in the Messier 51 galaxy system, captured by NASA's Chandra X-ray Observatory. X ray: NASA/CXC/Univ of Texas/E.Schlegel et al; Optical: NASA/STScI hide caption

toggle caption X ray: NASA/CXC/Univ of Texas/E.Schlegel et al; Optical: NASA/STScI

The Mars rover InSight will not launch as scheduled in March. A seismometer it was supposed to carry has experienced a series of vacuum leaks and cannot be repaired in time. Yang Lei/Xinhua/Landov hide caption

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A detail of an image captured by NASA's Curiosity Mars rover shows exposed layers of mudstone and sandstone in contact with one another. NASA/JPL-Caltech/MSSS hide caption

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Ceres, with bright spots in its Occator Crater, is seen here in a "false color" image that reflects its surface composition. New analysis says the spots are caused by a type of salt. NASA/JPL-Caltech/UCLA/MPS/DLR/IDA hide caption

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Pluto's shoreline of Sputnik Planum is seen in the highest-resolution images yet to come from New Horizons. John Spencer of the Southwest Research Institute says the details support the idea that the mountains "are huge ice blocks that have been jostled and tumbled and somehow transported to their present locations." NASA/JHUAPL/SwRI hide caption

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A building called Sustainability Base, at NASA's Ames Research Center in Mountain View, Calif., has an energy-efficient design that allows in sunlight. So for most of the year, the interior is illuminated by natural light. Dominic Hart/NASA hide caption

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Extravehicular crewmember 2 (EV2) Terry Virts is reflected in the helmet visor of EV1 Barry Wilmore during Extravehicular Activity 29 (EVA 29). Earth is in the background. Courtesy of NASA hide caption

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