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Astronomers Find Three Smallest Planets Outside Solar System

smallest alien planets
(Image credit: NASA/ JPL-Caltech)

Astronomers have discovered the three smallest alien planets yet, including one that's just the size of Mars.The alien worlds, detected using publicly available data from NASA's Kepler mission, are 0.78, 0.73 and 0.57 times the diameter of Earth, respectively; the smallest one is roughly Mars-size. Staff is the premier source of space exploration, innovation and astronomy news, chronicling (and celebrating) humanity's ongoing expansion across the final frontier. We transport our visitors across the solar system and beyond through accessible, comprehensive coverage of the latest news and discoveries. For us, exploring space is as much about the journey as it is the destination.