Notes

There are many things of why Mercury is a fascinating planet to me:

First, the fact that a year in Mercury is 88 days, while a Mercury day is 176 Earth days! The differences caused by Mercury is tidally locked to the Sun (like our Moon to the Earth) and gradually in time, the rotation orbit is almost in a match with the Sun. Hence, the planet itself is more recognized as a star (more like evening and morning star); even in ancient Greek, the 'evening star' is called Hermes while 'morning star' is Apollo.

Then, Mercury is the second hottest planet despite its name is always mentioned first for planets in Solar System. It is simply because Mercury has a thin atmosphere surrounds it. Because of this thin-to-none presence of an atmosphere, Mercury does not have any 'shield' to protect itself from any asteroids that pass by; hence, it has many impact craters than any other planets in Solar System.

Finally, the first discovery of a detailed surface Mercury. It happened in 1974 by Mariner 10 with three fly-bys and managed to capture half of the surface! For the first time, to be able to map the entire features by showing many impact craters (and the biggest craters, Caloris Basin, with a diameter of 1,550 km), then between the craters; exist plains which is the proof of much ancient lava or volcano (that has been inactive for a certain of period) !