Venus is a terrestrial planet in the inner Solar System, the second planet from the Sun and Earth’s closest planetary neighbor. It is comparable to Earth in size and mass but has a dense, carbon dioxide–dominated atmosphere producing a strong Greenhouse effect and a globally clouded sky of sulfuric acid aerosols. Mean surface temperature is about 737 K (464 °C), with surface pressure near 92 bar, making it the hottest planet in the solar system despite receiving less solar energy than Mercury. Its mean radius is 6,051.8 km and mass 4.867 × 10^24 kg. Venus has no natural satellites. These properties are summarized by NASA’s planetary fact sheets and overview materials. NASA Planetary Fact Sheet; NASA Venus Facts; Britannica.

Orbit, rotation, and illumination

• –Venus orbits at a mean distance of about 108.2 million km (0.72 AU) with a sidereal orbital period of 224.7 Earth days and very low eccentricity (~0.007). Its sidereal rotation period is about −243 Earth days (retrograde), while the mean solar day is ~116.8 Earth days; the Sun therefore rises in the west and sets in the east. Axial tilt is about 177° (effectively a flipped spin axis). These parameters are tabulated by NASA and Britannica. NASA Fact Sheet; Britannica.
• –With a high geometric/Bond albedo (~0.69/0.77) from its global cloud deck, Venus is the brightest planet as seen from Earth, reaching visual magnitude about −4.6 and displaying phases over a synodic period of ~584 days, an observation central to early heliocentric proofs. NASA Fact Sheet; NASA Venus Facts.

Atmosphere and climate

• –Composition is ~96.5% CO₂ and ~3.5% N₂ with trace gases including SO₂, H₂O, CO, HCl, HF, and noble gases; mean surface pressure is ~92 bar and mean surface temperature ~737 K. NASA Fact Sheet; Britannica.
• –Clouds of sulfuric acid aerosols span roughly 50–70 km altitude, defining a multilayered cloud deck. Above, the middle/upper atmosphere contains CO formed by CO₂ photodissociation and a complex sulfur chemistry; Venus Express investigations constrained cloud microphysics and chemistry. ESA Venus Express overview; ESA Acid clouds and lightning.
• –The upper atmosphere exhibits “super‑rotation,” with winds transporting the cloud tops around the planet in ~4 Earth days and zonal speeds near ~100 m/s, varying with latitude and time. ESA Venus Express overview; ESA winds analysis.
• –Lightning on Venus remains debated. Venus Express reported whistler‑mode electromagnetic waves near 100 Hz consistent with lightning discharges; other searches have set stricter limits, and optical confirmation is rare. Nature (Russell et al. 2007); ESA VEX lightning note; GRL 2023 review.

Surface and geology

• –Below the clouds, Magellan’s radar mapped ~98% of the surface at ~100–300 m resolution, revealing widespread volcanic plains, coronae, rifts, and tectonically deformed highlands. Impact crater density implies a geologically young surface, with resurfacing styles still under study. NASA Magellan mission summary; NASA Magellan fact; NASA history note.
• –Tesserae are rugged, highly deformed terrains with intersecting ridge–trough patterns that are among the oldest surfaces on the planet and key to understanding crustal evolution. Britannica—tesserae; USGS/encyclopedia entry.
• –Maxwell Montes (in Ishtar Terra) is the highest mountain complex on Venus, rising nearly 11 km above the mean planetary radius; the adjacent Cleopatra impact crater is ~100 km across. JPL Photojournal PIA00149; Britannica—Maxwell Montes.
• –Evidence for present‑day volcanism has strengthened. A study of repeat Magellan images found a volcanic vent at Maat Mons that expanded and changed shape between early and late 1991, interpreted as an eruptive event. Science (Herrick & Hensley, 2023); JPL news. Re‑analyses in 2024 identified radar signatures of new lava in Sif Mons and Niobe Planitia during the Magellan era, suggesting activity comparable in vigor to Earth’s in places. Nature Astronomy (2024); JPL summary; Reuters report.

Observation and appearance from Earth

• –Venus is typically the third brightest natural object in Earth’s sky after the Sun and Moon, visible as the “morning” or “evening” star and showing phases analogous to the Moon’s over a synodic period of ~584 days; nearest approaches are on the order of 38 million km. NASA Venus Facts.

Exploration

• –Early in situ knowledge came from the Soviet Venera program, whose landers and the Pioneer Venus Multiprobe sampled the atmosphere and, in several cases, survived minutes to hours on the surface, confirming the hot, high‑pressure conditions and enabling landmark surface imagery. NASA Venus Facts; NASA Pioneer Venus 2; NSSDC Venera images.
• –NASA’s [Magellan (spacecraft)] radar‑mapped the globe (1990–1994), transforming geologic understanding. NASA Magellan mission; NASA history.
• –ESA’s Venus Express (2006–2014) documented atmospheric dynamics, chemistry, and the 4‑day super‑rotation, and investigated cloud microphysics and the polar vortices. ESA VEX overview; ESA south‑polar vortex.
• –JAXA’s Akatsuki entered orbit in 2015 after an initial insertion failure, imaging atmospheric structure and gravity waves; contact was lost in April 2024, and operations were formally terminated on September 18, 2025. JAXA mission page; JAXA press release, Sept. 18, 2025 (JP); NASA mission note.

Current questions and upcoming missions

• –Reported 2020 detections of phosphine (PH₃) in the clouds sparked interest in potential disequilibrium chemistry or biology, but independent analyses and SOFIA aircraft observations set strict upper limits (~≤0.8 ppb) and found no compelling evidence; the issue remains open to targeted re‑measurement. Nature Astronomy debate; GRL SOFIA upper limit; NASA SOFIA update.
• –NASA’s DAVINCI will probe the atmosphere from top to near‑surface, including tessera descent imaging; as of 2025, NASA materials indicate a launch target around 2029–2030 with atmosphere entry early next decade. NASA Goddard DAVINCI feature; NASA mission page.
• –VERITAS, an orbiter to map topography and surface composition at high resolution, was delayed to no earlier than 2031 following a 2022 programmatic review. NASA/JPL announcement; NASA HQ release.
• –ESA’s EnVision, adopted in January 2024, targets a November 2031 launch to investigate interior–surface–atmosphere coupling with advanced radar and spectroscopy. ESA EnVision factsheet; ESA EnVision mission.

Nomenclature and cultural notes

• –Named for the Roman goddess Venus (Greek Aphrodite), the planet lends names of women (mythic and real) to most surface features; exceptions include Maxwell Montes. NASA Venus Facts; JPL PIA00149.

Internal links used: Solar System, Greenhouse effect, [Magellan (spacecraft)], Venera program, Akatsuki, NASA.