Author: Fraser Cain

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The Earth is the largest of the terrestrial planets in the Solar System, and the 3rd planet from the Sun. Are you looking for the circumference and diameter of the Earth?

The equatorial circumference of the Earth is 40,075 km. This is the distance around the equator of the Earth. If you measure the circumference of the Earth, while passing through the poles, the distance is only 40,007 km. This is because the Earth isn’t a perfect sphere. It’s rotating rapidly, which causes the equator to bulge out.

The equatorial diameter of the Earth is 12,756 km. This is the diameter of the Earth measured from one side of the Earth, passing through the center. If you go from pole to pole through the center, the distance is only 12,713 km.

We have written several articles about Earth for Universe Today. Here’s an article about the Earth’s magnetic field, and here’s an article about the surface area of Earth.

If you’d like more info on Earth, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

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The first planet from the Sun is Mercury, orbiting the Sun at an average distance of 57.91 million km. It’s also the smallest planet in the Solar System, measuring just 4,879 kilometers across. Mercury is named after the Roman god of commerce; he was the same entity as the Greek god Hermes – the messenger of the gods.

Mercury is a desolate, sun-baked world pockmarked by impact craters. It lacks any atmosphere, so the intense heat from the Sun escapes back into space on the planet’s night side. At noon on Mercury’s equator, temperatures can rise to 700 kelvin (426 °C), but on the night side of Mercury, it dips down to 100 kelvin (-173 °C). But Mercury isn’t the hottest planet in the Solar System; that’s actually Venus – its heat-trapping atmosphere boosts its temperature to 735 kelvin (461 °C).

Early astronomers didn’t even realize that Mercury was a single planet. They thought that it was actually two separate planets; one for when Mercury was seen after sunset, and another object for when it was seen in the morning before sunrise. Even the first rudimentary telescope couldn’t resolve the surface of Mercury, and it wasn’t until the first mission to pass Mercury in 1974, that astronomers could really see what Mercury looked like.

Mercury takes 88 days to complete one orbit around the Sun. Compare this to Venus, which takes 224.7 days, and Earth which takes 365.25 days. Since Mercury is the first planet in the Solar System, it has the fastest orbit, and then each planet has a successively longer orbit. Mercury’s day is almost as long as its year; 58.6 days.

It’s the smallest planet in the Solar System, but it’s the second densest. It has a density of 5.427 g/cm³. This is just after Earth, with a density of 5.515 g/cm³. Astronomers think that Mercury has a large metallic core, surrounded by a rocky mantle and a thin crust of rock. It doesn’t seem to have any active volcanism, but there might still be some venting of gasses which cont into a thin atmosphere around Mercury.

Mercury has no rings or moons.

We have written many articles about the first planet from the Sun. Here’s an article all about Mercury, and here’s some additional information about Mercury.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We’ve also recorded an entire episode of Astronomy Cast all about Mercury. Listen here, Episode 49: Mercury.

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The equatorial circumference of the Moon is 10,916 km. And the circumference of the Moon in miles is 6,783 miles. So, if you wanted to drive your lunar rover around the Moon and return back where you started, you’d need to travel 10,916 kilometers.

Need some comparison? The equatorial circumference of the Earth is 40,075 km. That makes the size of the Moon’s circumference about 27.24% the size of the Earth.

The Moon isn’t the largest moon in the Solar System – it only has an equatorial radius of 1,737.4 km. The largest moon is Jupiter’s moon Ganymede, with an equatorial radius of 2,634 km. That means Ganymede’s circumference is 16,550 km; bigger than the Moon’s circumference by about 5,634 km.

Want some more measurements?

The circumference of the Moon in meters: 10,916,000 meters
The circumference of the Moon in centimeters: 1,091,600,000 centimeters
The circumference of the Moon in feet: 35,813,648 feet
The circumference of the Moon in inches: 429,763,780 inches

We’ve written many articles about the Moon for Universe Today. Here’s an article about the full Moon, and here’s an article about the atmosphere of the Moon.

If you’d like more info on the Moon, check out NASA’s Solar System Exploration Guide on the Moon, and here’s a link to NASA’s Lunar and Planetary Science page.

We’ve also recorded an entire episode of Astronomy Cast all about the Moon. Listen here, Episode 113: The Moon, Part 1.

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The equatorial circumference of Saturn is 378,675 km (or 235,298 miles). Not that it’s actually possible, but if you wanted to drive your car around Saturn’s equator, that’s how far you’d have to travel. Just for comparison, the equatorial circumference of Earth is 40,075 km, so Saturn’s circumference is 9.4 times larger than the Earth.

Want to make the calculation for yourself? Well, the formula for calculating the circumference of a circle is 2 x pi x r, where R is the radius of the circle. The equatorial radius of Saturn is 60,268 km, so you can do the math yourself.

Of course, Saturn isn’t the largest planet in the Solar System, that’s Jupiter. Jupiter’s circumference is 449,197 km, or 1.19 times bigger than Saturn. And the largest object in the Solar System is the Sun, with an equatorial circumference of 4,379,000 km. That’s 11.56 times bigger than Saturn.

We’ve written many articles about Saturn for Universe Today. Here’s an article about what Saturn’s rings are made of, and here’s an article about how many moons Saturn has.

If you’d like more info on Saturn, check out Hubblesite’s News Releases about Saturn. And here’s a link to the homepage of NASA’s Cassini spacecraft, which is orbiting Saturn.

We’ve also recorded an episode of Astronomy Cast all about Saturn. Listen here, Episode 59: Saturn.

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Jupiter is the 5th planet from the Sun, and the largest planet in the Solar System. How much bigger is Jupiter than Earth? Just to give you a sense of scale, Jupiter is 2.5 times more massive than all the rest of the planets in the Solar System combined.

Jupiter’s diameter is 11.2 times larger than Earth. In other words, you could put 11.2 Earths side-by-side to match the diameter of Jupiter.

And Jupiter’s volume is even bigger. It would take 1321.3 Earths to fill up the volume of Jupiter. In terms of surface area, Jupiter is 121.9 times bigger than the Earth. That’s how many Earths could be flattened out to cover the surface of Jupiter.

Jupiter has 317.8 times the mass of the Earth.

Even though Jupiter is an enormous, massive planet, it’s much smaller than the Sun. The Sun accounts for 99.86% of the mass of the Solar System. You could fit 109 Earths side by side to match the diameter of the Sun, and it would take 1.3 million planets the size of the Earth to fill it up.

We’ve written many articles about Jupiter for Universe Today. Here’s an article about pictures of Jupiter, and here’s an article about missions to Jupiter.

If you’d like more information on Jupiter, check out Hubblesite’s News Releases about Jupiter, and here’s a link to NASA’s Solar System Exploration Guide to Jupiter.

We’ve also recorded an episode of Astronomy Cast just about Jupiter. Listen here, Episode 56: Jupiter.

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The equatorial circumference of Mars is 21,344 km (or 13,263 miles). This is the distance you would have to go if you wanted to travel completely around the equator of Mars.

You can calculate the Mars circumference on your own if you want. The equatorial radius of Mars is 3,397 km, so you can just use the mathematical formula, C = 2 x Π x Radius. Did you get the same answer?

And just for comparison, the equatorial circumference of Earth is 40,075 km. So the circumference of Mars is 53% of the circumference of Earth.

Like many of the planets in the Solar System, Mars is rotating on its axis, turning once every 24.6 hours. This rotation causes Mars’ equator to bulge out from the center of the planet. If you wanted to drive around the planet, passing through each of its poles, you would have a shorter journey because of this. This is called the meridional circumference, and for Mars, this is only 21,244 km.

We have written many articles about Mars for Universe Today. Here’s an article with some pictures of planet Mars, and here’s an article about the temperature of Mars.

If you’d like more info on Mars, check out Hubblesite’s News Releases about Mars, and here’s a link to the NASA Mars Exploration home page.

We’ve also recorded an episode of Astronomy Cast all about Mars. Listen here, Episode 52: Mars.