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Data collected by a NASA spacecraft as it flew past the innermost planet, Mercury, in January has confirmed that the planet is shrinking as it core cools, scientists reported Thursday. In a series of papers published in the journal Nature, scientists said that images of the planet performed by the MESSENGER spacecraft as it flew past the planet in January spotted features called lobate scarps, huge cliffs created in the planet's crust as it contracts. That contraction is caused because the planet's iron core is cooling; that core also drives a magnetic field whose existence was first discovered by the Mariner 10 spacecraft in the mid-1970s but confirmed and better analyzed by MESSENGER. Spacecraft observations also led scientists to conclude that the planet's plains were formed by volcanic activity early in its history,... [read full story]
