A solar-powered airplane finished crossing the United States on Saturday, landing in New York City after flying over the Statue of Liberty during its historic bid to circle the globe, the project team said. The spindly, single-seat experimental aircraft, dubbed Solar Impulse 2, arrived at New York's John F. Kennedy International Airport at about 4 a.m. local time after it took off about five hours beforehand at Lehigh Valley International Airport in Pennsylvania, the team reported on the airplane's website. Such a pleasure to land in New York! For the 14th time we celebrate sustainability," said the project's co-founder Andre Borschberg on Twitter after flying over the city and the Statue of Liberty during the 14th leg of the trip around the globe. The Swiss team flying the aircraft in a campaign to build support for clean energy technologies hopes eventually to complete its circumnavigation in Abu Dhabi, where the journey began in March 2015. The solar cr...
The surface of the innermost planet is unusually dark, and scientists now think they know why. Scientists analysing data from Nasa's Mercury Messenger spacecraft now think this mystery darkening agent is carbon in the form of graphite. This graphite may be a relic of the planet's primordial crust, which was later covered up by volcanism. The findings are published in the journal Nature Geoscience. Patrick Peplowski from the Johns Hopkins University Applied Physics Laboratory (APL) in Maryland and colleagues analysed measurements of the darkest parts of Mercury's surface taken by Messenger at the end of its mission.
They found that the darkest "stuff" on Mercury had a carbon-rich composition and that it was associated with large impact craters. According to the team, this association is consistent with the dark material coming from deeper within the planet and being exposed when space rocks gouged it out. Like Earth's Moon and the other inner planets, Mercury likely had a global magma ocean when it was young and the surface was very hot. "As this magma ocean cooled and minerals began to crystallise, minerals that solidified would all sink with the exception of graphite, which would have been buoyant and would have accumulated as the original crust of Mercury," said Rachel Klima, also from APL.
But this primordial crust was obscured by later volcanism and other geological processes. Some of this carbon-rich material would then have been mixed into the overlying rocks to cause a global darkening of Mercury's surface. "If we've really identified the remains of Mercury's original crust, then understanding its properties provides a means for understanding Mercury's earliest history," Patrick Peplowski explained.
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