Size and Distance :

With a radius of 3,760 miles (6,052 kilometers), Venus is roughly the same size as Earth — just slightly smaller.

From an average distance of 67 million miles (108 million kilometers), Venus is 0.7 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. It takes sunlight 6 minutes to travel from the Sun to Venus.

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Orbit and Rotation :

Venus' rotation and orbit are unusual in several ways. Venus is one of just two planets that rotate from east to west. Only Venus and Uranus have this "backwards" rotation. It completes one rotation in 243 Earth days — the longest day of any planet in our solar system, even longer than a whole year on Venus. But the Sun doesn't rise and set each "day" on Venus like it does on most other planets. On Venus, one day-night cycle takes 117 Earth days because Venus rotates in the direction opposite of its orbital revolution around the Sun.

Venus makes a complete orbit around the Sun (a year in Venusian time) in 225 Earth days or slightly less than two Venusian day-night cycles. Its orbit around the Sun is the most circular of any planet — nearly a perfect circle. Other planet's orbits are more elliptical, or oval-shaped.

With an axial tilt of just 3 degrees, Venus spins nearly upright, and so does not experience noticeable seasons.

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Internal structure :

Venus, represented without its atmosphere and showing its internal structure. Based on a false-color global radar view from Magellan.

Without seismic data or knowledge of its moment of inertia, little direct information is available about the internal structure and geochemistry of Venus. The similarity in size and density between Venus and Earth suggests they share a similar internal structure: a core, mantle, and crust. Like that of Earth, the Venusian core is at least partially liquid because the two planets have been cooling at about the same rate The slightly smaller size of Venus means pressures are 24% lower in its deep interior than Earth's. The principal difference between the two planets is the lack of evidence for plate tectonics on Venus, possibly because its crust is too strong to subduct without water to make it less viscous. This results in reduced heat loss from the planet, preventing it from cooling and providing a likely explanation for its lack of an internally generated magnetic field. Instead, Venus may lose its internal heat in periodic major resurfacing events.

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Atmosphere and climate :

Cloud structure in the Venusian atmosphere in 2018, revealed by observations in the two ultraviolet bands by Akatsuki

Planet Venus - viewed by the Parker Solar Probe (July 2020)

Venus has an extremely dense atmosphere composed of 96.5% carbon dioxide, 3.5% nitrogen - both being supercritical fluids at surface, and traces of other gases including sulfur dioxide. The mass of its atmosphere is 93 times that of Earth's, whereas the pressure at its surface is about 92 times that at Earth's—a pressure equivalent to that at a depth of nearly 1 km (5⁄8 mi) under Earth's oceans. The density at the surface is 65 kg/m3, 6.5% that of water or 50 times as dense as Earth's atmosphere at 293 K (20 °C; 68 °F) at sea level. The CO2-rich atmosphere generates the strongest greenhouse effect in the Solar System, creating surface temperatures of at least 735 K (462 °C; 864 °F). This makes Venus' surface hotter than Mercury's, which has a minimum surface temperature of 53 K (−220 °C; −364 °F) and maximum surface temperature of 700 K (427 °C; 801 °F), even though Venus is nearly twice Mercury's distance from the Sun and thus receives only 25% of Mercury's solar irradiance. This temperature is higher than that used for sterilization.

Venus' atmosphere is extremely enriched of primordial noble gases compared to that of Earth. This enrichment indicates an early divergence from Earth in evolution. An unusually large comet impact or accretion of a more massive primary atmosphere from solar nebula have been proposed to explain the enrichment. However, the atmosphere is also depleted of radiogenic argon, a proxy to mantle degassing, suggesting an early shutdown of major magmatism.