royalsociety
@rfuebmiliag
#OnThisDay in 1671, astronomer Giovanni Cassini first observed Saturn's moon Iapetus. Iapetus is a strange beast, with one light hemisphere and one dark hemisphere, and a huge equitorial ridge of some of the Solar System's tallest mountains: #Astronomy https://t.co/dH7zuZxQTR https://t.co/RgGU7ZUkEE
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