The Inca site of Machu Picchu may have been built at least 20 years earlier than we thought. Spanish accounts from the 16th century suggest it was constructed after 1438, but using enhanced carbon dating, researchers say human remains at the citadel are from 1420 . A vast lake believed to have been present in Gale crater on Mars may have been smaller than we thought. Analysing data collected by the Curiosity rover, researchers say just 1 per cent of the rocks - those in the deepest parts of the crater - formed in a lake. A robotic thumb strapped to a user's hand next to their little finger can be used well enough to act as an 11th digit while playing piano. Both amateur and experienced players learned to control the thumb, which is manipulated by moving their foot, within an hour.
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