March 18, 2026
Venus Facts: Everything You Need to Know About Earth's Twin
Venus is the second planet from the Sun and the hottest world in our solar system. Often called Earth's twin because of its similar size and mass, Venus is in reality a world of extremes — with surface temperatures hot enough to melt lead, an atmosphere dense enough to crush a submarine, and clouds made of sulfuric acid. Named after the Roman goddess of love and beauty, Venus is the brightest natural object in the night sky after the Moon, visible as the "morning star" or "evening star" depending on the season. Despite being our closest planetary neighbor, Venus remained hidden beneath its opaque cloud cover until radar mapping and Soviet landers revealed its volcanic hellscape. This complete guide covers everything we know about Venus: its size, diameter, surface area, physical features, crushing atmosphere, retrograde rotation, and the missions that unveiled its secrets — all drawn from NASA's Planetary Fact Sheets and decades of exploration data.
Photo credit: Unsplash
Venus Fact File
How Big Is Venus?
Venus is the sixth-largest planet in the solar system and Earth's nearest match in size. Its equatorial diameter is 12,104 km (7,521 miles) — roughly 95% of Earth's 12,756 km. The difference between the two planets is only 652 km, which means if you placed Venus next to Earth, you would struggle to tell them apart by size alone. Unlike most planets, Venus has virtually no polar flattening — its polar and equatorial diameters are nearly identical because the planet rotates so slowly that centrifugal forces barely distort its shape.
The surface area of Venus is 460.2 million km² (177.7 million square miles), about 90% of Earth's total surface area. Its mass is 4.867 × 10²&sup4; kg, approximately 81.5% of Earth's, producing a surface gravity of 8.87 m/s² — about 90% of what you feel standing on Earth. A 70 kg person would weigh roughly 63 kg on Venus. This near-Earth gravity, combined with similar bulk density (5.24 g/cm³ vs. Earth's 5.51 g/cm³), is why Venus earned the nickname "Earth's twin" — though the resemblance ends at the surface.
Venus by the Numbers
Venus orbits the Sun at an average distance of 108.2 million km (0.723 AU), completing one orbit every 224.7 Earth days. Its orbit is the most circular of any planet in the solar system, with an eccentricity of just 0.0068 compared to Earth's 0.0167. But the truly extraordinary number is Venus's rotation period: it takes 243 Earth days to complete a single rotation on its axis — longer than its year. This means a day on Venus (one full rotation) is actually longer than a Venusian year (one full orbit around the Sun).
To make things even stranger, Venus rotates retrograde — from east to west — the opposite direction of most planets. Because the retrograde spin partially cancels the orbital motion, a solar day on Venus (sunrise to sunrise) lasts about 116.75 Earth days, shorter than its sidereal day. The axial tilt of 177.4° is sometimes described as "nearly upside down," which is another way of interpreting the retrograde rotation. Venus comes closer to Earth than any other planet, passing within about 38.2 million km at inferior conjunction — making it our nearest planetary neighbor.
The Crushing Atmosphere
Venus has the densest atmosphere of any rocky planet. The surface pressure is 92 bar — equivalent to the pressure 900 meters beneath Earth's oceans. If you stood on the surface, you would experience the same crushing force as a deep-sea submersible. The atmosphere is 96.5% carbon dioxide with 3.5% nitrogen and traces of sulfur dioxide, water vapor, and carbon monoxide. This massive blanket of CO&sub2; creates the most extreme greenhouse effect in the solar system, raising the surface temperature to an average of 465 °C (869 °F) — hotter than Mercury, despite being nearly twice as far from the Sun.
The temperature is remarkably uniform across the entire planet. Day and night, equator and poles, the surface stays within a few degrees of 465 °C. The thick atmosphere acts as a thermal blanket, redistributing heat so efficiently that there is essentially no weather at the surface — just a dim, orange-tinted twilight beneath 65 km of cloud. The cloud deck itself is made of sulfuric acid droplets (H&sub2;SO&sub4;) and extends from roughly 45 to 70 km altitude. These clouds reflect about 75% of incoming sunlight, making Venus brilliantly bright in Earth's sky, but they trap infrared radiation escaping from below, sustaining the runaway greenhouse effect.
Scientists believe Venus may have once had liquid water on its surface billions of years ago. As the Sun gradually brightened, surface water evaporated, adding water vapor (a potent greenhouse gas) to the atmosphere, which raised temperatures further, evaporating more water — a runaway feedback loop. Eventually, ultraviolet radiation split the water molecules apart, and the hydrogen escaped to space. What remains is a bone-dry world where the atmospheric water content is less than 0.002%. Venus serves as a cautionary tale for understanding greenhouse effects on Earth.
Physical Features of Venus
Venus's surface is dominated by two continent-sized highland regions. Ishtar Terra, roughly the size of Australia, sits in the northern hemisphere and contains Maxwell Montes — the tallest mountain on Venus at approximately 11 km above the mean surface level (comparable to Earth's Mauna Kea measured from the ocean floor). Ishtar Terra also features the high plateaus of Lakshmi Planum, bordered by rugged mountain ranges. In the southern hemisphere, Aphrodite Terra stretches nearly 10,000 km along the equator — about the size of South America — and contains deep rift valleys and fractured terrain that suggest tectonic activity.
Venus hosts over 1,600 major volcanic features, more than any other body in the solar system. These include large shield volcanoes like Maat Mons (8 km high) and Sif Mons, as well as features unique to Venus: pancake domes — steep-sided, flat-topped volcanic structures 20–50 km across and about 1 km tall, formed by the eruption of highly viscous lava under the crushing atmospheric pressure. Corona structures — circular volcanic-tectonic features ranging from 100 to 2,600 km in diameter — dot the surface, possibly formed by mantle plumes rising beneath the crust.
Notably, Venus has relatively few impact craters (about 1,000), and they are distributed almost uniformly across the surface. None are smaller than about 3 km in diameter — the thick atmosphere burns up or breaks apart smaller impactors before they reach the ground. The even distribution and relatively young apparent age of the craters led scientists to hypothesize that Venus's entire surface was catastrophically resurfaced by volcanic activity roughly 300–500 million years ago, erasing its earlier geological record.
Surface and Terrain
Nearly everything we know about Venus's surface comes from radar mapping, because the thick cloud cover makes visual observation impossible from orbit. NASA's Magellan spacecraft, which orbited Venus from 1990 to 1994, mapped 98% of the surface using synthetic aperture radar (SAR) at a resolution of about 100 meters. The resulting images revealed a world shaped almost entirely by volcanism: vast rolling plains of solidified lava flows cover about 80% of the surface, with highland regions (terrae) making up the remaining 20%.
The surface features extensive lava channels, some stretching thousands of kilometers. Baltis Vallis, the longest known channel in the solar system, runs for 6,800 km — longer than the Nile River. These channels were carved by extremely fluid lava, possibly composed of carbonatite or sulfur-rich compounds that remain liquid at Venus's extreme temperatures. The surface also shows tesserae — regions of highly deformed, ridged terrain that may represent the oldest surviving crust, pre-dating the global volcanic resurfacing event.
At the surface, conditions are otherworldly. The atmosphere is so dense that it refracts light dramatically, bending the horizon upward — a person standing on Venus would perceive the surface curving up around them rather than falling away. The dim orange light filtering through 65 km of cloud creates perpetual twilight, roughly comparable to a heavily overcast day on Earth. Wind speeds at the surface are only about 0.3–1.0 m/s — a gentle breeze — but because the atmosphere is so dense, even these slow winds exert significant force on anything in their path.
Why Venus Rotates Backwards
Venus is one of only two planets in the solar system that rotates retrograde (Uranus being the other, though its extreme tilt is a separate phenomenon). On Venus, the Sun rises in the west and sets in the east. The planet takes 243 Earth days to complete one rotation — the slowest of any planet — meaning its sidereal day is longer than its 224.7-day year. Several theories attempt to explain this unusual rotation.
The most widely discussed hypothesis is a giant impact early in Venus's formation that either flipped the planet or dramatically slowed and reversed its spin. Another leading theory involves atmospheric thermal tides: the Sun heats Venus's thick atmosphere asymmetrically, creating a gravitational torque that, over billions of years, could have gradually slowed the planet's rotation to a near-standstill and then reversed it. A third possibility is that Venus originally rotated prograde but with a very high axial tilt (close to 180°), which is mathematically equivalent to a slow retrograde rotation with low tilt. The question remains one of the most intriguing puzzles in planetary science.
Missions to Venus
Venus has been explored by over 40 spacecraft since the 1960s, though its hostile environment makes surface missions extraordinarily challenging. The Soviet Venera program achieved a series of remarkable firsts: Venera 7 became the first spacecraft to successfully land on another planet (1970), and Venera 9 returned the first photographs from the surface of another world (1975). Venera 13 (1982) survived for 127 minutes on the surface — the longest of any Venus lander — transmitting color images and the first audio recordings of another planet's surface (the sound of Venusian wind). No lander has survived longer; the extreme heat and pressure destroy electronics rapidly.
NASA's Magellan orbiter (1990–1994) transformed our understanding of Venus by radar-mapping 98% of its surface. ESA's Venus Express (2006–2014) studied the atmosphere and discovered evidence of recent volcanic activity, including transient hotspots and fresh-looking lava flows. JAXA's Akatsuki, currently orbiting Venus, studies atmospheric dynamics including the mysterious "super-rotation" — upper atmosphere winds that circle the planet in just 4 Earth days, 60 times faster than Venus rotates.
A new wave of Venus missions is now in development. NASA's VERITAS (Venus Emissivity, Radio science, InSAR, Topography, and Spectroscopy) will map Venus's surface at far higher resolution than Magellan, searching for active volcanism and tectonic processes. NASA's DAVINCI (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) will send an instrumented descent sphere through the atmosphere, sampling gases all the way down and capturing close-up images of the surface during descent. ESA's EnVision orbiter will complement these missions with high-resolution radar and spectrometry. Together, these missions aim to answer fundamental questions: Is Venus still volcanically active? Did it once have oceans? And could microbial life exist in its temperate cloud layers?
Frequently Asked Questions About Venus
▶What is the size of Venus?
Venus has an equatorial diameter of 12,104 km (7,521 miles), making it 95% the size of Earth. Its total surface area is 460.2 million km². Venus is the sixth-largest planet in our solar system and the closest in size to Earth, which is why the two are often called sister planets or twins.
▶How big is Venus compared to Earth?
Venus is nearly the same size as Earth. Its diameter is 95% of Earth’s, its mass is 81.5% of Earth’s, and its surface gravity is 90% of Earth’s. A 70 kg person would weigh about 63 kg on Venus. Despite these similarities, conditions on Venus are radically different — surface temperatures reach 465 °C and atmospheric pressure is 92 times Earth’s.
▶What is the diameter of Venus in km?
The equatorial diameter of Venus is 12,104 km (7,521 miles). Unlike most planets, Venus has almost no polar flattening — its polar diameter is essentially the same as its equatorial diameter because the planet rotates so slowly. For comparison, Earth’s equatorial diameter is 12,756 km, making Venus only 652 km narrower.
▶Why is Venus so hot?
Venus is the hottest planet in the solar system due to a runaway greenhouse effect. Its thick atmosphere is 96.5% carbon dioxide, which traps solar energy and raises the surface temperature to an average of 465 °C (869 °F) — hot enough to melt lead. The dense cloud layers of sulfuric acid also reflect sunlight but trap infrared radiation, creating an insulating blanket that keeps the surface uniformly scorching, day and night.
▶Why does Venus spin backwards?
Venus rotates retrograde — from east to west — the opposite direction of most planets. The leading theory is that a massive collision with a large body early in Venus’s history flipped or reversed its spin. Another hypothesis suggests that tidal interactions between Venus’s thick atmosphere and the Sun gradually slowed and reversed its rotation over billions of years. The result is that on Venus, the Sun rises in the west and sets in the east.
▶What are the main physical features of Venus?
Venus’s major physical features include Maxwell Montes (the tallest mountain at 11 km above mean surface level), Ishtar Terra and Aphrodite Terra (two continent-sized highland regions), over 1,600 major volcanic features including shield volcanoes and unique pancake domes, and vast rolling plains covered in solidified lava flows. The surface was mapped almost entirely by NASA’s Magellan spacecraft using synthetic aperture radar.
Explore More
Want to test your knowledge of Venus and the other planets? Our Solar System games challenge you to sort planets by properties, identify worlds from clues, and compare planetary extremes. Venus is just the beginning — explore all eight planets and discover what makes each one unique.
Sources
- NASA Planetary Fact Sheet. "Venus Fact Sheet." nssdc.gsfc.nasa.gov.
- NASA Solar System Exploration. "Venus: In Depth." solarsystem.nasa.gov/venus.
- NASA Jet Propulsion Laboratory. "Magellan Mission to Venus." science.nasa.gov.
- ESA Space Science. "Venus Express: Mission Summary." esa.int/Science_Exploration.
- NASA Discovery Program. "VERITAS and DAVINCI Missions." discovery.nasa.gov.
- Soviet Academy of Sciences. "Venera Program Results." Archived mission reports.