This is smaller than the orbit of Mercury around the Sun.

This makes the Venusian surface hotter than Mercury's, which has a minimum surface temperature of and maximum surface temperature of , even though Venus is nearly twice Mercury's distance from the Sun and thus receives only 25 of Mercury's solar irradiance.

Its mass is roughly half that of the planet Mercury.

The inner terrestrial planets consist of Mercury, Venus, Earth, and Mars.

Ganymede, the largest of these, has a diameter greater than that of the planet Mercury.

Both Mariner 10 and MESSENGER performed this maneuver to reach Mercury.

At in diameter, Callisto has about 99 the diameter of the planet Mercury but only about a third of its mass.

Mars is the fourth planet from the Sun and the second smallest planet in the Solar System, after Mercury.

The radius of the planet's orbit is 7 million kilometres, about 0.047 astronomical units, or one eighth the radius of Mercury's orbit.

__TOC__ Moons by primary Mercury, the innermost planet, has no moons, or at least none that can be detected to a diameter of .

For example, Venus is approximately 0.33 AU farther out from the Sun than Mercury, whereas Saturn is 4.3 AU out from Jupiter, and Neptune lies 10.5 AU out from Uranus.

For comparison, the non stellar objects in our Solar System with maximum visible magnitudes below 2.50 are the Moon ( 12.92), Venus ( 4.89), Jupiter ( 2.94), Mars ( 2.91), Mercury ( 2.45), and Saturn ( 0.49).

It's three times hotter than Mercury, which is right next to the Sun. Now, briefly, here's an image you've seen, as one of the only old images, but I show it because I want to briefly give you CSI Climate.

In the earlier period between 3.8 and 4.1 Ga, changes in the orbits of the gas giant planets may have caused a late heavy bombardment by asteroids that pockmarked the Moon and the other inner planets (Mercury, Mars, and presumably Earth and Venus).

Up until recently, that was the Solar System four Earth like planets with small radius, smaller than about two times the size of the Earth and that was of course Mercury, Venus, Mars, and of course the Earth, and then the two big, giant planets.

The stars and planets were carried around the Earth on spheres or circles, arranged in the order (outwards from the center) Moon, Sun, Venus, Mercury, Mars, Jupiter, Saturn, fixed stars, with the fixed stars located on the celestial sphere.

But here we see the complex trajectory of the Cassini mission color coded for different mission phases, ingeniously developed so that 45 encounters with the largest moon, Titan, which is larger that the planet Mercury, diverts the orbit into different parts of mission phase.