Which Two Planets Are Closer to the Sun Than the Earth?

Mercury: Size and Distance

• Mercury has a highly elliptical orbit. Its distance from the sun ranges from a minimum of 29 million miles to a maximum of 43 million miles, with an average distance of 36 million miles. Mercury has a radius of 1,516 miles, about 38 percent that of Earth. It is only slightly larger than Earth's moon. By mass, it is 5.5 percent as large as the Earth, or 3.30104 x 10^23 kg. When Mercury and Earth are at their closest, they are 48 million miles apart. At their farthest, they are 137 million miles apart.

Venus: Size and Distance

• Venus has a more circular orbit than Mercury. Its distance from the sun ranges from a minimum of 66.8 million miles to a maximum of 67.7 million miles, with an average distance of 67.2 million miles. Venus has a radius of 3,760 miles, about 95 percent that of Earth. By mass, it is 81.5 percent as large as the Earth, or 4.86732 x 10^24 kg. When Venus and Earth are at their closest, they are 23.7 million miles apart. At their farthest, they are 162 million miles apart.

Mercury: Other Properties

• Mercury has very little atmosphere and so is especially vulnerable to meteor impacts. Craters are visible all over its surface. Although it is the closest planet to the sun, it is not the planet with the highest temperature. Its thin atmosphere does not hold much heat, and temperatures fluctuate between negative 279 degrees Fahrenheit at night and 801 degrees Fahrenheit during the day. Mercury's year is about 88 Earth days long, and its day is about 59 Earth days long. That means Mercury completes fewer than two rotations on its axis during one orbit around the sun. Mercury's gravity is significantly less than that of Earth; if you weigh 100 pounds on Earth, you would only weigh 38 pounds on Mercury.

Venus: Other Properties

• Venus has a very thick atmosphere that is extremely high in carbon dioxide, which creates a runaway greenhouse effect. Venus is the hottest planet in the solar system, with average temperatures around 864 degrees Fahrenheit -- well above the melting point of lead. Venus' gravity is only slightly less than that of Earth. If you weigh 100 pounds on Earth, you would weigh 91 pounds on Venus. Venus is also the most volcanically active planet in the solar system. Venus rotates on its axis in the opposite direction of most planets and takes 243 Earth days to complete one rotation. Its year is equal to 225 Earth days.