Mars had an oxygen-rich atmosphere around 4 billion years ago
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In 2011, archaeologists discovered the skeletal remains of a Roman couple who have been holding hands for 1,500 years.
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The focusing muscles of the eyes move around 100,000 times a day. To give your leg muscles the same workout, you would need to walk 80km (50 miles) every day.
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In Georgia, there is an airtight room called the Crypt of Civilization that was sealed in 1940. It contains numerous artefacts documenting what life was like at the time of sealing, and is scheduled to be opened in the year 8113 to show people of the future exactly what life was like.
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The oldest stone tools found are dated from 2.7 - 2.9 million years ago. The species that made these tools is unknown.
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