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What is the Hottest Planet in the Solar System?

Posted June 18, 2013

Earth is the third planet from the Sun, and the climate here is just right for life. Here in our Solar System, there are planets both hotter and colder than Earth.

So… which one is the hottest?

A global view of Mercury, as seen by MESSENGER. Credit: NASA

A global view of Mercury, as seen by MESSENGER. Credit: NASA

You might think it’s Mercury, the planet closest to the Sun. Mercury orbits at a distance of only 58 million kilometers, travelling in a blast-furnace of scorching radiation. Its temperature can skyrocket to 700 Kelvin, or 426 degrees Celsius on the sunward side. In the shadows, temperatures plunge down to 80 Kelvin, which is -173 degrees Celsius

Mercury sure is hot, but Venus is hotter.

Venus imaged by Magellan Image Credit: NASA/JPL

Venus imaged by Magellan Image Credit: NASA/JPL

Venus is much further from the Sun, orbiting at a distance of more than 108 million kilometers. Average temperature there is a hellish 735 Kelvin, or 462 degrees Celsius – hot enough to melt lead.

Venus remains that same temperature no matter where you go on the planet. At the North Pole? 735 Kelvin. At night? 735 Kelvin. Daytime at the equator? You get the point.

So, why is Venus so much hotter than Mercury, even though it’s further away from the Sun? It’s all about the atmosphere.

Mercury is an airless world, not unlike the Moon. Venus, has a very thick atmosphere of CO2, which adds incredible pressure, and traps in the heat.

Atmosphere of Venus. Credit: ESA

Atmosphere of Venus. Credit: ESA

Consider our own planet. When you stand at sea level on Earth, you’re experiencing one atmosphere of pressure. But if you could stand on the surface of Venus – and trust me, you don’t want to – you’d experience ninety-two times as much atmospheric pressure. This is the same kind of pressure as being a kilometer underneath the surface of the ocean.

Venus also shows us what happens when carbon dioxide levels just keep on rising. Radiation from the Sun is absorbed by the planet, and the infrared heat emitted is trapped by the carbon dioxide, which creates a runaway greenhouse effect.

You might think a planet this hot with such extreme temperature and pressure, would be impossible to explore.

And if you did, you’d be wrong.

The Soviets sent a series of spacecraft called Venera, which parachuted down through the thick atmosphere and returned images from the surface of Venus. Although the first few missions were failures, this taught the Soviets just how hellish the Venusian environment really is.

Surface of Venus by Venera.

Surface of Venus by Venera.

Venera 13 made it down to the surface in nineteen-eighty-one and survived for one-hundred-and-twenty-seven minutes, sending back the first color pictures of Venus’ surface.

The hottest planet in our solar system is Venus,

When it comes to temperature, distance from the Sun matters, but it takes a backseat to wrapping a planet in a atmospheric blanket of carbon dioxide.

Source: Universe Today, story by Fraser Cain

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