Venus Explained Simply

The puzzle at the heart of Venus

Why is Venus hotter than Mercury, even though Mercury sits closer to the Sun and receives more direct sunlight? It seems backwards, until you look at what each planet is wrapped in.

Why Venus stays hot from surface to cloud tops

Mercury has almost no atmosphere, so the heat it absorbs from the Sun escapes again just as fast. Venus is sealed inside a thick blanket of carbon dioxide roughly 90 times heavier than Earth's air. That blanket lets sunlight in but won't let the heat back out, so Venus keeps cooking, day after day, year after year, until it settled at a surface temperature of around 464°C. That's hot enough to melt lead, zinc and tin.

Venus in a quick set of facts

Unlike Earth, Venus stays roughly the same scorching temperature everywhere, at every time of day. Its thick atmosphere spreads heat around the whole planet instead of letting the night side cool down.

Venus's orbit and position

What lies beneath the clouds?

From space, Venus looks like a smooth, bright, creamy marble, because you are not looking at the ground at all. You're looking at the top of an unbroken layer of cloud that never clears, never breaks, and never lets ordinary cameras see through it. Underneath is a rocky surface with volcanoes, vast lava plains, mountain belts and impact craters, but no camera in orbit has ever photographed it directly in visible light.

So How Do We Know What The Surface Looks Like?

This is one of the more satisfying puzzles in planetary science, and the answer is radar, the same basic idea as a ship's sonar, but using radio waves instead of sound. A spacecraft in orbit fires radio waves straight down. Radio waves pass through thick cloud the way sound passes through fog, hit solid ground, and bounce back up. By timing how long the echo takes and measuring how it changes shape, scientists can build a height map of the surface, tall mountains reflect differently to flat plains, and rough lava fields reflect differently to smooth ones.

NASA's Magellan orbiter did most of this work between 1990 and 1994, mapping more than 98% of the surface this way without a single visible-light photograph. Almost everything we know about Venus's mountains, volcanoes and craters comes from radar, not cameras.

How Venus Formed, And Where It Went Wrong

Venus and Earth formed from the same swirl of dust and rock, at almost the same size, at almost the same time, roughly 4.5 billion years ago. For a long time, scientists suspect, Venus may even have had oceans of liquid water. But sitting closer to the Sun meant Venus started slightly warmer than Earth, and that small head start triggered a chain reaction now called a runaway greenhouse effect: warmer oceans evaporated faster, water vapour trapped more heat, more heat evaporated more ocean, and so on, until every drop of surface water was gone and the carbon dioxide that Earth's oceans and rock lock away safely was instead left free in the air, thickening the atmosphere into the crushing blanket it has today.

Gravity And Weight, Explained With Real Numbers

Gravity is the pulling force that gives you weight, and every planet pulls differently depending on its size and mass. Venus is very close to Earth in both, so its gravity feels almost the same. If you weigh 100 kg on Earth, here's roughly what the scale would say elsewhere in the Solar System. Your body hasn't changed in any of these; only the strength of the pull has.

Of every rocky planet, Venus is the closest match to Earth's gravity, which is exactly why its atmosphere and surface conditions feel so shocking by comparison.

What Would A Day On Venus Actually Feel Like?

Consider stepping onto the surface, somehow protected for just a few minutes. The sky above isn't blue or black; it's a dim, hazy orange, because sunlight has to fight through tens of kilometres of cloud before it reaches the ground. There's no wind on your skin worth mentioning; surface breezes on Venus barely reach walking pace. But you would already be in serious trouble: the air pressure around you is the same as being almost a kilometre under Earth's ocean, and the heat is well past anything a human body, or most machines, can survive.

The Sun itself would barely seem to move. A single Venusian day, sunrise to sunrise, lasts 243 Earth days, longer than the entire Venusian year of 225 Earth days. That oddity happens because Venus rotates on its axis extremely slowly, and backwards compared with most planets, so if you could survive to see it, the Sun would appear to rise in the west and set in the east.

Nothing built by humans has lasted long down there. The Soviet Venera 13 lander holds the surface-survival record: it operated for 127 minutes in 1982 before the heat and pressure destroyed it, the longest any spacecraft has functioned on Venus's surface.

Could people ever live above Venus?

Not on the surface, not with any technology that exists today. The pressure would crush an unprotected human in seconds, the heat would be fatal almost instantly, and the clouds are made of sulfuric acid droplets instead of water. It's a genuinely hostile world at ground level.

But there's a curious exception. About 50–60 km above the surface, inside the cloud layer, Venus's atmospheric pressure and temperature briefly pass through something close to Earth-like, around room temperature, around Earth sea-level pressure. That narrow "sweet spot" is why some scientists have seriously proposed floating, balloon-supported habitats high in the Venusian atmosphere, instead of surface bases, as the more realistic long-term idea. Nothing like this has been attempted yet; it remains a research concept.

Earth and Venus: similar size, different worlds

Every Major Mission, In Order

Space missions are how a distant bright dot in the sky becomes a real, mapped, measured world. Venus has actually been visited more times than any other planet; it's a relatively short trip, which made it an early target for both the US and Soviet space programmes.

Common Myths About Venus

Venus's name and appearance lead to a few persistent misunderstandings. Here's what's actually true.

Why Venus matters to planetary science

Venus is similar to Earth in size, but its surface is hidden beneath thick clouds and is hot enough to melt lead. It is the hottest planet in the Solar System.

Inside the cloud-covered planet

Diagram is simplified for beginner learning and is not drawn to scale.

The short history of visiting Venus

That makes Venus unusual among the planets: it's one of the best-mapped worlds in the Solar System in terms of surface geography, yet it remains one of the least explored up close, simply because nothing built so far can survive there for long. Everything scientists know about its rocks and volcanoes comes from a handful of short-lived landers and decades of orbital radar, not from boots on the ground.

Venus facts that surprise people

• Venus rotates in the opposite direction to almost every other planet, a day there technically ends with a sunrise in the west.
• A single day on Venus (243 Earth days) is longer than its entire year (225 Earth days).
• The surface pressure is around 92 times Earth's sea-level pressure, similar to being nearly a kilometre deep in Earth's oceans.
• Venus is usually the brightest planet in our night sky, and sometimes the third-brightest natural object overall, after the Sun and Moon.
• Its clouds circle the entire planet in about four Earth days, far faster than Venus itself rotates, a mystery known as "super-rotation."
• The longest any spacecraft has survived on the surface is 127 minutes, set by the Soviet Venera 13 lander in 1982.

Venus by the numbers

What Venus connects to next

Continue from Venus to see why Earth avoided a runaway greenhouse and why Mars lost much of its early atmosphere.

Previous: Mercury Next: Earth

Compare Venus’s runaway greenhouse atmosphere with Earth’s life-supporting climate system and Mars’s thin, cold atmosphere. Then return to the eight-planet comparison or read how spacecraft map and measure hostile worlds.