Venus

Venus
	Near-global view of Venus in natural colour, taken by the MESSENGER space probe
Designations
Pronunciation	/ˈviːnəs/ ⓘ
Named after	Roman goddess of love (see goddess Venus)
Adjectives	Venusian /vɪˈnjuːziən, -ʒən/, rarely Cytherean /sɪθəˈriːən/ or Venerean / Venerian /vɪˈnɪəriən/
Symbol
Orbital characteristics
	Epoch J2000
Aphelion	0.728213 AU (108.94 million km)
Perihelion	0.718440 AU (107.48 million km)
Semi-major axis	0.723332 AU (108.21 million km)
Eccentricity	0.006772
Orbital period (sidereal)	224.701 d; 0.615198 yr; 1.92 Venus solar day;
Orbital period (synodic)	583.92 days
Average orbital speed	35.02 km/s
Mean anomaly	50.115°
Inclination	3.39458° to ecliptic; 3.86° to Sun's equator; 2.15° to invariable plane;
Longitude of ascending node	76.680°
Argument of perihelion	54.884°
Satellites	None
Physical characteristics
Mean radius	6,051.8±1.0 km; 0.9499 Earths;
Flattening	0
Surface area	4.6023×108 km2; 0.902 Earths;
Volume	9.2843×1011 km3; 0.857 Earths;
Mass	4.8675×1024 kg; 0.815 Earths;
Mean density	5.243 g/cm3
Surface gravity	8.87 m/s2; 0.904 g;
Escape velocity	10.36 km/s (6.44 mi/s)
Synodic rotation period	−116.75 d (retrograde) ; 1 Venus solar day
Sidereal rotation period	−243.0226 d (retrograde)
Equatorial rotation velocity	6.52 km/h (1.81 m/s)
Axial tilt	2.64° (for retrograde rotation); 177.36° (to orbit)
North pole right ascension	18h 11m 2s; 272.76°;
North pole declination	67.16°
Albedo	0.689 (geometric); 0.76 (Bond);
Temperature	232 K (−41 °C) (blackbody temperature)
Surface absorbed dose rate	2.1×10−6 μGy/h
Surface equivalent dose rate	2.2×10−6 μSv/h; 0.092–22 μSv/h at cloud level
Apparent magnitude	−4.92 to −2.98
Absolute magnitude (H)	−4.4
Angular diameter	9.7″–66.0″
Atmosphere
Surface pressure	93 bar (9.3 MPa); 92 atm
Composition by volume	96.5% carbon dioxide; 3.5% nitrogen; 0.015% sulfur dioxide; 0.0070% argon; 0.0020% water vapour; 0.0017% carbon monoxide; 0.0012% helium; 0.0007% neon; Trace carbonyl sulfide; Trace hydrogen chloride; Trace hydrogen fluoride;
	Defining the rotation as retrograde, as done by NASA space missions and the USGS, puts Ishtar Terra in the northern hemisphere and makes the axial tilt 2.64°. Following the right-hand rule for prograde rotation puts Ishtar Terra in the negative hemisphere and makes the axial tilt 177.36°.;

Venus is the second planet from the Sun. It has the densest atmosphere of all rocky bodies in the Solar System, so dense that at surface level and 92 atmospheres, it is a supercritical fluid. The planet's surface is dominated by volcanoes – there are 167 Venusian volcanoes that are over 100 km (60 mi) across. Venus has a diameter roughly equal to Earth's at 12,104 km (7,521 mi) and is classified as a terrestrial planet.

The surface of Venus has unique features of volcanic origin, such as 'farras' which are wide pancake-like lava domes and 'arachnoids' which are concentric fractures resembling spider webs. It is thought that the planet's crust is releasing internal heat through active volcanism and shaping the surface with large resurfacing. Above, Venus's atmosphere has a rough composition of 96.5% carbon dioxide, 3.5% nitrogen, and reflective sulfuric acid cloud cover. Venus has a weak induced magnetosphere.

Venus has a solar year that is 224.7 Earth days long and a solar day that is 117 Earth days long. Its dense atmosphere is the reason why the planet has a slow retrograde rotation and an extreme greenhouse effect. This is demostrated by Venus's average and consistent surface temperature of 464 °C (867 °F). Geological processes on Venus are relatively slow as shown by lack of erosion in craters, though there are some evidence that the planet still has active volcanism. Venus has no natural satellite.

Like other planets in the Solar System, Venus was formed approximately 4.5 billion years ago. As of the early 2020s, it is suggested that Venus's atmosphere might be similar to one surrounding the early Earth and there may have been substantial quantities of surface liquid water. Back then, Venus might have been more conducive to life. Over billions of years, solar forcing and large volcanic resurfacing may have eroded the initial atmosphere and created the new carbon dioxide-rich atmosphere.

Venus is the third brightest object in Earth's sky after the Moon and the Sun, therefore it has been important in human culture. Venus was the second planet to be visited by humans, with the first flyby by the Mariner 2 probe in 1962, the first atmospheric entry by the Venera 4 probe in 1967, the first successful landing by the Venera 8 probe in 1972 and the first orbiting probe by Venera 9 in 1975. As of 2024, there is no active probe on Venus, though it is a subject of three missions as a gravity assist waypoint.

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[13] Defining the rotation as retrograde, as done by NASA space missions and the USGS, puts Ishtar Terra in the northern hemisphere and makes the axial tilt 2.64°. Following the right-hand rule for prograde rotation puts Ishtar Terra in the negative hemisphere and makes the axial tilt 177.36°.