Venus
Venus is the second planet from the Sun and the closest planet to Earth. It's often called Earth's "twin" because it's almost exactly the same size, but the comparison ends there. Venus is the hottest planet in the solar system, with crushing atmospheric pressure, sulphuric acid clouds, and a surface hot enough to melt lead. It's the most hostile place in the solar system to visit.
- Position 2nd planet between Mercury and Earth
- Distance from Sun 108 million km 0.72 times Earth's distance
- Diameter 12,104 km 95% of Earth's
- Day length 243 Earth days longer than its year!
- Year length 225 Earth days second-shortest year
- Surface temp 465°C hottest planet, hotter than Mercury
Where Venus sits
Venus is the second planet from the Sun, sitting between Mercury and Earth. It orbits the Sun at an average distance of about 108 million km. Of all the planets, Venus comes closest to Earth, sometimes as little as 38 million km away. That's about a hundred times further than the Moon.
Venus vs Earth
Earth's "twin" is almost identical in size but a totally different world
Venus is 95% the diameter of Earth, the closest in size of any planet. From space the two look nearly the same size.
Venus's gravity is 91% of Earth's. A 50 kg person would weigh approx. 45 kg on Venus. You'd hardly notice the difference.
Venus's day is longer than its year. It rotates so slowly that one full spin takes 243 Earth days, but one orbit only takes 225.
Venus is the hottest planet in the solar system, even hotter than Mercury. Its thick atmosphere traps heat in a runaway greenhouse effect.
Standing on Venus would feel like being 900 metres underwater on Earth. The pressure would crush an unprotected person almost instantly.
Venus has no moons. It's one of only two planets in the solar system with no natural satellites (Mercury is the other).
The hottest planet
You might expect Mercury to be the hottest planet because it's closest to the Sun. But Venus, which is twice as far away, is significantly hotter. The reason is its atmosphere.
Venus has a very thick atmosphere made of about 96% carbon dioxide. Carbon dioxide traps heat. The Sun's energy comes in, warms the surface, and then can't escape back into space because the CO2 reflects it back down. This is called the greenhouse effect, and on Venus it's run away completely. The surface temperature is the same everywhere on the planet, day or night, north or south: about 465°C. Hot enough to melt lead, tin, or zinc.
Clouds of sulphuric acid
Above the surface, Venus is covered in thick yellow clouds. These clouds are not made of water, like Earth's clouds. They're made of sulphuric acid. The clouds form a layer approx. 20 km thick, between 50 and 70 km above the surface. If you were inside them, you wouldn't see anything, and the acid would dissolve almost any material it touched.
Strangely, between the clouds and the surface, the air is mostly clear. If you could somehow survive on Venus, the view from the ground would be of a hazy red sky with no clouds visible at all.
Spinning backwards
Venus is one of only two planets that spin backwards compared to the rest. On Earth, Mars, Jupiter and most other planets, the Sun rises in the east and sets in the west. On Venus, the Sun rises in the west and sets in the east. And it does so very slowly, just twice per Venusian year, because the day is longer than the year.
Why does Venus spin backwards?
Scientists aren't completely sure. The most popular theory is that early in the solar system's history, Venus was hit by a planet-sized object. The collision was so violent it flipped Venus completely upside down. After that, what was once rotating forwards became rotating "backwards" from our point of view, even though the planet itself didn't change direction. Another idea is that the thick atmosphere acted like a brake, slowing down and eventually reversing the planet's spin over billions of years.
The Venusian landscape
Beneath its clouds, Venus is a volcanic world. There are over 1,600 major volcanoes, more than on any other planet. Some of them may still be active today. The largest is Maat Mons, which is 8 km tall. The surface is covered in vast plains of solidified lava, mountain ranges, deep canyons, and giant craters from ancient asteroid impacts.
Two huge highland regions stand out: Ishtar Terra (about the size of Australia) and Aphrodite Terra (the size of South America). Almost all features on Venus are named after women from history or mythology.
The Morning Star and Evening Star
Venus is the brightest natural object in our night sky after the Moon. It often outshines every star and can even cast faint shadows on a moonless night. Because it's closer to the Sun than Earth, Venus is only ever visible just before sunrise or just after sunset. For this reason, ancient cultures often gave it two different names:
- The Morning Star when it appears in the eastern sky before dawn.
- The Evening Star when it appears in the western sky after sunset.
It took a long time for ancient astronomers to realise these were the same object.
Missions to Venus
Venus has been visited by more spacecraft than any other planet except Mars. Most have been Soviet missions in the 1960s, 70s and 80s. The Soviet Venera series of landers were the only spacecraft to successfully touch down on Venus. Even then, they only survived for between 23 minutes and two hours before the heat and pressure destroyed them. The photos they sent back are still the only images we have of the surface.
NASA has two upcoming missions called DAVINCI and VERITAS that are planned for the 2030s. They'll study Venus's atmosphere and surface in unprecedented detail.
Could humans live on Venus?
Not on the surface. The heat alone would kill an unprotected person in seconds, and the pressure would crush them flat. Even the sulphuric acid clouds wouldn't be friendly.
But interestingly, some scientists have suggested that floating cities could one day exist 50 km above Venus's surface. At that altitude the temperature is mild (approx. 25°C), the pressure is about the same as on Earth, and ordinary air would actually float in Venus's heavy atmosphere like a hot-air balloon. It's still science fiction for now, but it's not impossible.