Baltis Vallis is a sinuous channel on

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...

ranging from wide and ~ long, slightly longer than the

Nile The Nile, , Bohairic , lg, Kiira , Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered the longest ...

and the longest known channel of any kind in the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

. It is thought the channel once held a river of

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

. It is a single channel over most of its length, but

anastomoses An anastomosis (, plural anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be norm ...

in several sections, for lengths of up to . There appear to be other, smaller channels in the same area, down to the limit of resolution, some of which seem to be tributaries of Baltis Vallis. The lava must have had a very low viscosity, possibly due to a

carbonatite Carbonatite () is a type of intrusive or extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geochemical verification. Carbonati ...

composition. At the volcano

Ol Doinyo Lengai Ol Doinyo Lengai (Oldoinyo Lengai), "Mountain of God" in the Maasai language, is an active volcano located in the Gregory Rift, south of Lake Natron within the Arusha Region of Tanzania, Africa. Part of the volcanic system of the East African Ri ...

in Tanzania,

natrocarbonatite Natrocarbonatite is a rare carbonatite lava which erupts from the Ol Doinyo Lengai volcano in Tanzania within the East African Rift of eastern Africa. Natrocarbonatite lavas were first documented in 1962, by J B Dawson. Composition Whereas mo ...

lava erupts at around , not far above Venus's mean ambient temperature of . Analysis of cross-sectional profiles (using brightness data from ''

Magellan Ferdinand Magellan ( or ; pt, Fernão de Magalhães, ; es, link=no, Fernando de Magallanes, ; 4 February 1480 – 27 April 1521) was a Portuguese explorer. He is best known for having planned and led the 1519 Spanish expedition to the East ...

synthetic aperture radar Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes. SAR uses the motion of the radar antenna over a target region to provide fine ...

images) indicates that while Baltis Vallis does have levees, primarily in its first , and intrachannel ridges, mainly in the segment from the source, the feature is primarily erosional, with a bottom surface below the surrounding plains at 90% of the sites studied. The average depths and widths of the channel are 46 ± 16 m and 2.2 ± 0.4 km, respectively. The channel is located in an area consisting entirely of plains and wrinkle ridges. The formation of the channel may be associated with a single event that emplaced a large unit that type of volcanic terrain. The topography of the channel undulates over a range of over , with some stretches traveling uphill, indicating that various regions have uplifted and/or subsided since the channel formed. At present, the terminus is slightly higher in elevation than the source. Both ends of the channel are obscured, so its original length is unknown. The channel was initially discovered by the Soviet Venera 15 and 16 orbiters which, in spite of their one-kilometer resolution, detected more than of the channel. Similar channel-like features are common on the plains of Venus. In some places they appear to have been formed by lava which may have melted or thermally eroded a path over the plains' surface. Most are wide. They resemble terrestrial meandering rivers in some aspects, with meanders, cutoff bows and abandoned channel segments. However, Venusian channels are not as tightly sinuous as terrestrial rivers. Most are partly buried by younger lava plains, making their sources difficult to identify. A few have vast radar-dark plains units associated with them, suggesting large flow volumes. These channels with large deposits appear to be older than other channel types, as they are crossed by fractures and wrinkle ridges, and are often buried by other volcanic materials. In addition, they appear to run both upslope and downslope, suggesting that the plains were warped by regional tectonism after channel formation.

References

* {{Venus Volcanism on Venus Volcanic landforms Lava channels