Venus: Facts About the Solar System’s Hottest Planet

Venus is the second planet from the Sun and one of the four rocky planets of the inner solar system. It is slightly smaller than Earth, but beneath its bright clouds lies a profoundly different world. Venus comes closer to Earth than any other planet and is also the brightest planet seen from Earth. Its brilliance has made it a familiar sight since ancient times, usually appearing before sunrise or after sunset.

Venus Quick Facts

Venus Is Earth’s Twin in Size, Not Conditions

Venus is often described as Earth’s twin because the two planets are remarkably similar in size and basic composition. Venus is about 95% as wide as Earth, has roughly 82% of its mass and produces about 90% of Earth’s surface gravity. Both are rocky planets believed to have an iron-rich core surrounded by a rocky mantle and crust.

The resemblance largely ends there. Venus developed a dense atmosphere, extreme surface temperatures and conditions profoundly different from those on Earth—making the two planets an important example of how similarly sized worlds can evolve along very different paths.

The Atmosphere and Crushing Surface Pressure

Venus has the densest atmosphere of any rocky planet in the solar system. It consists of about 96.5% carbon dioxide and 3.5% nitrogen, with clouds containing droplets of sulfuric acid. These clouds completely obscure the surface in visible light, which is why spacecraft must use radar to map the landscape below. At the surface, the atmospheric pressure is about 92 times greater than at sea level on Earth—comparable to the pressure nearly 900 meters (3,000 feet) beneath Earth’s oceans.

Why Venus Is the Hottest Planet

Although Mercury is closer to the Sun, Venus is the hottest planet in the solar system. Its average surface temperature is about 464°C (867°F)—hot enough to melt lead—and varies remarkably little between day and night or between the equator and poles. The cause is an extreme greenhouse effect. Sunlight passes through the atmosphere and warms the surface, but the dense carbon dioxide atmosphere prevents much of that energy from escaping back into space as heat. Venus may once have experienced more moderate conditions, although scientists do not yet know whether liquid water ever persisted on its surface.

A Volcanic Surface Hidden Beneath the Clouds

Radar observations reveal a landscape dominated by broad volcanic plains, immense lava flows, mountains, valleys and thousands of volcanic features. Venus does not appear to have Earth-like plate tectonics, but heat rising from its interior has extensively reshaped and deformed the crust.

Venus is not merely a world of extinct volcanoes. Comparisons of radar images taken by NASA’s Magellan spacecraft in the early 1990s revealed a volcanic vent changing shape and areas where fresh lava apparently flowed between observations. This provides direct evidence that eruptions occurred recently in geological terms and that Venus remains volcanically active.

A Day on Venus Is Longer Than Its Year

Venus takes about 243 Earth days to complete one rotation on its axis, but only 224.7 Earth days to orbit the Sun. In this rotational sense, a day on Venus lasts longer than a Venusian year. This refers to its sidereal day—the time required to rotate once relative to the distant stars. The interval from one sunrise to the next is shorter, lasting about 117 Earth days. A location on Venus would therefore experience roughly two sunrises during each orbit of the Sun.

Why Does Venus Rotate Backward?

Venus rotates from east to west, opposite to Earth and most other planets. Viewed from above the solar system’s north pole, this is called retrograde rotation. As a result, the Sun would appear to rise in the west and set in the east on Venus. Scientists do not know exactly how this unusual rotation developed. A major collision early in the planet’s history may have altered its spin, while gravitational tides from the Sun and forces produced by its dense atmosphere may also have slowed or reversed the rotation over time. Uranus also rotates retrograde, so Venus is not the solar system’s only “backward” planet.

Why Venus Has No Moons

Venus has no natural moons and no ring system. There is no confirmed explanation for this, although its proximity to the Sun means solar gravity has a stronger influence over objects orbiting the planet than it does around more distant worlds. Venus may once have possessed a moon that was lost following a collision or changes in the planet’s rotation, but this remains hypothetical. Some asteroids temporarily follow Venus around the Sun in special arrangements known as quasi-satellite orbits, but they are not gravitationally bound moons of the planet.

Spacecraft Exploration of Venus

More than 40 missions have been launched toward Venus, although not all were successful. NASA’s Mariner 2 completed the first successful flyby of another planet in 1962. The Soviet Venera program later achieved the first successful landing on another planet and returned the first photographs from the surface of Venus. NASA’s Magellan orbiter used radar to map almost the entire planet between 1990 and 1994. More recently, ESA’s Venus Express and Japan’s Akatsuki studied its atmosphere and climate, with Akatsuki’s mission ending in 2025.

A new period of exploration is planned for the early 2030s. NASA’s DAVINCI will send a probe through the atmosphere, while VERITAS will map the surface and interior from orbit. ESA’s Envision mission, currently planned for launch in 2031, will investigate how the planet’s geology, atmosphere and climate interact.

Why Venus Has Phases

Because Venus orbits closer to the Sun than Earth does, we see different portions of its sunlit hemisphere as the planets move around their orbits. Through a telescope, Venus displays a complete sequence of phases resembling those of the Moon, from a thin crescent through half and gibbous phases to nearly full.

Its apparent size also changes dramatically. Venus looks largest as a crescent when it is relatively close to Earth and smallest when its almost fully illuminated hemisphere faces us from the far side of the Sun. Galileo’s observation of these phases in 1610 provided important evidence that Venus orbits the Sun rather than Earth.

How to Find and Observe Venus

Venus is usually easy to identify because it is brighter than any star. Since it orbits closer to the Sun than Earth, it never appears far from the Sun in our sky. Look for it low in the west after sunset when it is the “evening star,” or low in the east before sunrise when it is the “morning star.” Its visibility changes throughout the year, so an astronomy app can confirm when and where to look.

Even a small telescope will reveal its changing phases, while observations over several weeks show noticeable changes in both phase and apparent size. Venus is often easiest to view during twilight, when the brighter sky reduces its intense glare. Its permanent cloud cover prevents ordinary telescopes from revealing surface features.

Safety warning: Never search for Venus with binoculars or a telescope while the Sun is above the horizon unless the Sun is safely blocked from view. Looking at the Sun through magnifying optics can damage the retina within seconds and may cause permanent vision loss.

Why Venus Is Named After a Roman Goddess

Venus has been visible since prehistoric times, so it has no single discoverer. The Romans named the brilliant planet after Venus, their goddess of love and beauty, whose Greek counterpart was Aphrodite. It is the only planet named after a female deity, and most of its surface features are also named after historical or mythological women.

The usual modern adjective for something relating to the planet is Venusian. Cytherean is a valid but much less common alternative, derived from Cytherea—an ancient title for Aphrodite associated with the Greek island of Cythera. Contrary to a claim sometimes repeated online, Venusian is not merely a science-fiction term.