Venusi

Regional Level Types
Venus	Planet

A planet in our Solar System, second-closest to the Sun. Information on the composition (atmosphere, surface) is derived from Earth-based, Earth-orbital and spacecraft-based (incl. landers like Venera 9) science; also based on modelling.

The planet represents an extremely harsh environment, with a global mean surface temperature of ca. 740° K (467°C/872°F) and pressure of ca. 95 bar, the surface is extremely dry (ca. 20 ppm of H₂O).

The atmosphere is also harsh; the composition of the lower portion is: 96.5% CO₂, ~4% N₂ (2.5 in the more upper portions), 30-185 ppm SO₂, 40-150 ppm H₂O, 17-51 ppm CO, 3 ppm H₂S, with traces of HDO, HCl, COS, S_1-8, SO and HF.

The typical composition of the surface (information from 3 landers) in wt.% is: 45.1-48.7 SiO₂, 1.25-1.59 TiO₂, 15.8-17.9 Al₂O₃, 7.7-9.4 FeO, 0.14-0.2 MnO, 8.1-11.5 MgO, 7.1-10.3 CaO, 2-2.4 Na₂O, 0.1-4.0 K₂O, 0.88-4.7 SO₃.

Note on the mineral list: it is based on a normative composition taken from the results of the lander's analyses, taken exclusively from the volcanic plains and rises area; this has limitations, as the composition is based on XRF measurements, that include elements starting from Mg. Thus, this composition does not consider the possible presence of carbonate minerals, and some of the listed minerals may or may not exist in reality. Meanwhile, there are fluvial-like geological features on the planet, and it has been suggested that they may be connected with carbonatite lavas; some other geological formations were also supposed to be due to kimberlitic magmatism. Calcite is predicted to be stable; to be sure, the sulphuric acid rains are supposed to occur, but this concerns the upper atmosphere, and the compound is though to evaporate when in its lower part. Iron sulfides and anhydrite may be present in some of the Venusian regions.

Geological features

- Volcanic plains and rises: ca. 80% of the surface; landforms are usually typical of fluid basaltic lava; the post-accretion heat on Venus is mainly due to radioactivity of U, Th, and K; a (single) evidence of high Th content is suggestible of chemical differentiation; the surface is generally low in K, but there are exceptions; the basalts are similar to either MORB and alkaline Earth basalt types in Mg*, FeO/MnO and Ca/Al ratios, and abundance of Ti;
- Steep sided domes: scattered, together with "pancakes", among the volcanic plains; likely connected with the activity of more viscous magma;
- Long Channels or Canali: meandering features, may be as much as 6800 km long, incised into the plains or tesserae; the liquids responsible of the formation of canalli are basalt, liquid sulfur, carbonatite lavas, carbonate-sulfate lavas, or water;
- Venusian Highlands: their low radar reflectance indicates a possible occurrence of "heavy metal frost" in form of metal sulfides (e.g., galena) rather than previously thought elemental tellurium;
* Highland Plateaus: ca. 8% of the surface; often deformed by faults -> tessera; some internal parts seem to be resurfaced by basaltic lava flows
* Ishtar Terra: a unique feature resembling typical Earth's continent
* Low-emissivity deposits: concern the highest elevations, like Maxwell Montes around Ishtar Terra.

Coordinates:
Young provides that "[o]n Venus, longitude is measured from 0 to 360 degrees with the prime meridian centered within a small impact crater named Ariadne, located in Sedna Planitia..... Because Venus rotates in a clockwise direction as viewed looking down on the north pole, longitude on Venus increases in numerical value toward the east from the planet's prime meridian."

Other Databases

Wikipedia:	https://en.wikipedia.org/wiki/Venus
Wikidata ID:	Q313

Localities in this Region

References