Mercury's rotation

The rotation of Mercury was studied using its surface markings, and Schiaparelli found some, which he always saw in the same position. He concluded that Mercury always presented the same side to the sun, which was consistent with the Sun's tidal influences to produce this effect.
 Giovanni Schiaparelli Italy 1889 Mercury's rotation

The rotation of Mercury was studied using its surface markings, and Schiaparelli found some, which he always saw in the same position. He concluded that Mercury always presented the same side to the sun, which was consistent with the Sun's tidal influences to produce this effect.