That because Mercury is small, its core would have solidified longĪgo. During these visits, over 2,700 pictures were taken,Ĭovering 45% of Mercury's surface. It flew past Mercury for the second time and on Mafor It flew past the planet on Maat aĭistance of 705 kilometers from the surface. Mariner 10 spacecraft which was launched on Most of the scientific findings about Mercury comes from the Would take 10 9 years and would have raised the interior A model of this process shows that such a despinning Rapid as 8 hours, but over millions of years it was slowly despun by Scientists speculate that its rotation could have been as Mercury rotates one and a half times during each orbit.īecause of this 3:2 resonance, a day on Mercury (sun rise to sun rise) is 176Įarth days long as shown by the following diagram.ĭuring Mercury's distant past, its period of rotation may have beenįaster. Period was determined to be 58.646 +- 0.005 days.Īlthough Mercury is not tidally locked to the Sun, its rotational period is tidallyĬoupled to its orbital period. After close observation by the Mariner 10 spacecraft, the Later in 1971, Goldstein refined the rotation period to be 58.65 +- 0.25ĭays using radar observations. In 1965, Pettengill andĭyce determined Mercury's period of rotation to be 59 +- 5 days based upon radar It wasĮxpected to be much colder if it always faced away from the Sun. Mercury and determined that the dark side was too warm to be tidally locked. In 1962, radio astronomers looked at radio emissions from He determined that Mercury must be tidally locked to the Sun, just as the Moon is Than it would if Mercury was directly overhead.ĭuring the 1880's, Giovanni Schiaparelli drew a sketch showing faint features on Mercury. Is so low on the horizon that the light must pass through 10 times the amount of Earth's atmosphere Because of this, it can only be viewed duringĭaylight hours or just prior to sunrise or after sunset. At maximum elongation it is only 28ĭegrees from the Sun as seen from Earth. Until Mariner 10, little was known about Mercury because of theĭifficulty in observing it from Earth telescopes. As the explorer gazes out into space, he might see two bright The explorer would notice that the Sun appears twoĪnd a half times larger than on Earth however, the sky is alwaysīlack because Mercury has virtually no atmosphere to cause scattering of Kilometers in height and extend for hundreds of kilometers. Mercury's rolling,ĭust-covered hills have been eroded from the constant bombardment of If an explorer were to step onto the surface of Mercury, he wouldĭiscover a world resembling lunar terrain. Smaller than Earth and 40% larger than the Mercury was named by the Romans after theįleet-footed messenger of the gods because it seemed to move more
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