Why Is Venus the Hottest Planet?

Why Is Venus the Hottest Planet?

Although Venus is not the closest planet to the Sun, its atmosphere is extremely dense and stores heat in a way that triggers the greenhouse effect, in which the oceans boil away from the surface. Surface pressure on Venus is 90 times higher than on Earth.

The atmosphere consists of carbon dioxide and clouds of sulfuric acid. Nitrogen is present, but only in small amounts. As a result, the surface is hotter than that of Mercury.

During Venus’ evolution, the sun’s ultraviolet rays may have evaporated what little water Venus had, leaving the planet completely dry. Venus is full of volcanoes, and scientists have discovered 1600 of them so far, and those are just the big ones!

Venus Approaching the Sun
Venus Approaching the Sun

Venus, Cloudy with a Chance of Life

Venus is currently inhospitable, but it wasn’t always so. Missions have observed granite-like rocks there that require abundant water to form. In the early days of the solar system, when the sun was cooler, there may have been liquid water on the planet’s surface for 2 billion years – much longer than on Mars, which had liquid water for only 300 million years. Water is the key to life as we know it. So was there once life on Venus?

Scientists, including Planetary Society co-founder Carl Sagan, have predicted that life could exist in Venus’ upper atmosphere, which has Earth-like temperatures and pressures about 50 kilometers above the planet’s surface. There, mysterious dark spots absorb more than half of the planet’s solar energy. In 2020, scientists announced that they had found phosphine in the Venusian clouds, a chemical strongly associated with life – though the existence of the signal is still being verified.


We don’t know how Venus transformed from a potentially habitable world to its current hellish state. By studying Venus, scientists are learning how Earth-like planets evolve and what conditions prevail on Earth-sized exoplanets. Venus also helps scientists model Earth’s climate and serves as a cautionary tale of how dramatically a planet’s climate can change.

Venus Facts

  • Surface temperature: 820°F (440°C) to 900°F (480°C).
  • Average distance from the Sun: 108 million km (67 million miles), 38% closer to the Sun than Earth
  • Diameter: 12,104 km (7,521 miles), Earth is only 5% wider
  • Volume: 928 billion km3 (223 billion mi3), Venus could fit 1.1 times inside Earth
  • Gravity:9 m/s², 90% of the Earth’s gravity
  • Solar day: 243 earth days
  • Solar year: 225 earth days
  • Atmosphere: 96% carbon dioxide, 3% nitrogen, 1% other gases

 Why is Venus the hottest planet?

Venus is the second planet in orbit around the Sun. It was the first planet to be explored in 1970 by a space probe called Venera 7. The mission of Venera 7 was to measure the temperature of Venus’ atmosphere.

Named after the Roman goddess of beauty and love, this planet is anything but loving. Its environment is so hellish that spacecraft usually can’t survive long on its surface.

The Venera 7, for example, lasted only 23 minutes! It wasn’t until 1981, when Venera 13 flew through Venus’ hot atmosphere and landed on its surface, that we finally got color photos of Venus. Venera 13 was able to withstand 127 minutes of burning before it melted and the transmissions stopped.


After all these observations, scientists have found that Venus’ atmosphere is extremely dense, consisting of 96% carbon dioxide and 3.5% molecular nitrogen, which contributes to enormous heat storage.

During the day, the planets absorb energy from the sun, which is why temperatures heat up. At night, the energy is radiated back into space. On Venus, however, this is not quite the case.

Here, the infrared radiation (the re-radiated heat) must penetrate the dense atmosphere, which is very difficult. Therefore, the heat that the planet absorbs from the Sun is stored on its surface for long periods of time.


This phenomenon is called the “runaway greenhouse effect.” Because of this greenhouse effect, Venus is about 700 degrees hotter than currently known natural temperatures.

Early in the history of the solar system, a thinner atmosphere and a cooler sun would have brought Venus’ temperature closer to that of Earth, making life possible. Today, Venus is unable to support life due to the runaway process, the heat released, and the resulting high temperature.

Fun Facts about Venus:

Venus is sometimes referred to as Earth’s “poisonous twin”

The bodies of Earth and Venus are almost the same size, and the latter planet’s orbit is also closer to Earth than that of any other planet in the solar system. In addition, Venus is not the only planet that has thick clouds in its atmosphere; so does Earth, and both have relatively young surfaces.

But that’s where the similarities end – because as we know, Venus has a hellish atmosphere, while Earth’s high nitrogen content and relatively average oxygen content allow life to thrive.

Venus has lunar-like phases

One of the features of Venus that makes it so interesting is that it has phases not unlike those of the Moon. These phases can be easily observed from Earth with a telescope, and that is why Venus has always been studied.

There are many volcanoes on Venus

There are more volcanoes on Venus than on any other planet in the solar system. We currently know that there are over 1,600 volcanoes on the surface of this terrestrial planet, but there are probably many, many more that are too small for us to observe with the resources currently available to us.

Venus transits are extremely rare

Venus is one of the few planets that can be observed as it passes in front of the Sun (also called transiting). Venus transits are very rare, occurring less than once per century. The last two occurred in 2004 and 2012, and the next Venus transit is expected in 2117.

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