MERCURY
This minute world is arguably the least explored of the four terrestrial planets
Mercury is the smallest of all the planets in the Solar System and the closest planet to the Sun, but there’s so much more to it. Mercury is so tiny compared to the other planets that you can actually fit around 23,500 Mercurys into Jupiter, though it’s roughly 1,400 kilometres (870 miles) larger in diameter than the Moon.
The small planet orbits the Sun with less than half the distance between the Sun and Earth, resulting in it being ‘tidally locked’. Tidal locking occurs when an object is so close to its host that the gravity is overwhelmingly powerful; because of this influence, instead of continuously spinning on its axis like Earth does, the object has one side facing towards its host object at all times. In this case Mercury is tidally locked to the Sun. For every two revolutions around the Sun, Mercury rotates on its axis three times. Each orbit takes 88 Earth days, making a year on Mercury roughly a quarter of an Earth year.