science

The planet Mercury exhibits a phenomenon called 'Mercury Precession', which is similar to the moon's phases. Mercury precession is caused by a combination of the planet's very small axial tilt, its elliptical orbit around the sun and the sun's gravity. This causes the surface of Mercury to first appear brighter and then get darker, as it advances and retreats along its orbit. This phenomenon is similar to the waxing and waning of the moon, where the illuminated portion of the moon increases and then decreases in a repetitive cycle.