Mercury is the closest planet to the Sun and can only be seen either just after or just before sunrise. Mercury orbits the sun in just 88 days but takes nearly two months to rotate on its axis. As a result, Mercury's day and night each last 88 days. Mercury has almost no atmosphere and the temperature can reach 420 degrees in the 'daytime' and minus 180 degrees at 'night'.

Distance from Sun (million km): 57.9 57.9
Year (time to go round the Sun): 88 Earth days 88 Earth days
Day (time to revolve round axis): 58 days 15 hrs 30 mins
Diameter at equator (km): 4,878
Known moons: 0
Mass (Earth = 1): 0.055
Gravity at surface (Earth = 1): 0.38