Mercury circles the Sun the closest of any planet, with an average distance of only 57.9 million kilometers. Mercury is the planet that is nearest to the Sun. The second closest planet to the Sun is Venus, while the third closest planet to the Sun is Earth. Mars is too far away from the Sun to be considered a major factor in determining whether or not Mercury will be able to reflect light back to us during a solar eclipse.
Venus and Mars are both much farther away from the Sun than Mercury, so they do not affect how close or far away Mercury is from the Sun.
Earth's orbit around the Sun is elliptical, not circular. If Earth were a perfect sphere, it would be possible for it to come as close as 57.5 million km to the Sun and as far away as 61.5 million km, but on average Earth orbits at a distance of 60 million km.
Mars has no atmosphere and is therefore completely transparent to sunlight, but it also receives only 485 millimeters of rain per year, which is less than one tenth of a percent of what falls on Earth. The rest of Martian surface is made up of rocks, some of which may have been covered by water long ago. In addition to the 485 mm of rain, Mars also experiences outflows of gas from its interior, most notably oxygen and carbon dioxide.
Were you curious about which planet is nearest to the Sun? The planet Mercury is the answer. To give you a sense of scale, Venus circles the Sun at an average distance of 108.2 million kilometers.
Venus is the second-closest planet to the Sun, following only Mars. However, because Venus orbits closer to the Sun than does Earth, it passes through more solar eclipses. In addition, because Venus is also much larger than Earth, it blocks out more of the Sun from view.
Venus was originally called Vulcan, after the god of fire in Roman mythology. It was later named after the Greek god of love.
Closest approach: 0559 UTC on 5-6 June 2086. At this time, Venus will be about 466,000 km across, or 2% wider than it is today.
Far away: 930 AU (astronomical units), or about 50 times farther than Pluto's orbit around the Sun.
Mass: 7.3 billion tonnes (as compared to Earth's 5.98 billion).
Density: 592 kg/m3 (compared to Earth's 7771).
At their closest approach to the Sun, Venus and Mercury are the two planets. Mercury orbits at a distance of 58 million kilometers, whereas Venus circles at a distance of 108 million kilometers. Mercury takes 88 Earth days to complete an orbit, whereas Venus takes 225 days. Therefore, at their closest approach, Mercury and Venus take about 75% as long to circle the Sun as they do to complete one full orbit.
These two planets were not always known to be orbiting so closely to each other. In fact, for many years, astronomers believed that they was placed far enough away from each other that they could not have a solid surface to float on because they would hit each other every time that they turned around completely.
However, in 1847, American astronomer William C. Redfield noticed that when he plotted the positions of Venus against those of Mercury they seemed to be moving together in relation to the Sun, which showed that they must be close together relative to the Sun. A few months later, British astronomer Richard Carrington also found evidence of this relationship between these two planets using data collected by himself and others. He called their interaction "Mercury's dance with Venus."
Over the next few decades, more observations were made of these two planets and it became evident that they is very little space between them when they are at their closest approach.