Mercury is the innermost planet of the Solar System.
Except for that of the distant Pluto, mercury's elliptical orbit around the
Sun is the most out-of-round of any of the planets in our Solar System (the
difference between the maximum and minimum distances of mercury from the Sun
is as much as 40 per cent of the average distance, compared with less
than 4 per cent for the Earth. Its average distance from the Sun is
58 million kilometers, which is 4/10 of the Earth's average distance.
Thus mercury is 0,4 A.U. from the Sun. It is also, except for Pluto,
the least massive planet in our Solar System; it has only 5.1/2 per
cent the mass of the Earth.
Mercury's rotation
period around the Sun (solar rotation period) is 176 days, its
sideral rotation period is 59 days and its period of revolution is
88 days. We know from Kepler's second law that Mercury travels around
the Sun at different speeds in its eccentric orbit. This effect, coupled
with mercury's slow rotation on its axis, would lead to tan interesting
effect if we could stand on its surface. From some locations we would see
the Sun rise for an Earth day or two, and then retreat below the horizon
from which it had just come, when the speed of Mercury's revolution around
the Sun dropped below the speed of mercury's rotation on its own axis. Later
the Sun would rise again and then continue across the sky.