Baltis Vallis is a sinuous channel on

Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

ranging from wide and ~ long, slightly longer than the

Nile The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...

and the longest known channel of any kind in the

Solar System The Solar SystemCapitalization 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 "Sola ...

. 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 Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

. It is a single channel over most of its length, but anastomoses 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 rock, intrusive or extrusive rock, extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geoche ...

composition. At the volcano Ol Doinyo Lengai in Tanzania, natrocarbonatite lava erupts at around , not far above Venus's mean ambient temperature of . Analysis of cross-sectional profiles (using brightness data from '' Magellan''

synthetic aperture radar Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or 3D reconstruction, three-dimensional reconstructions of objects, such as landscapes. SAR uses the motion of the radar antenna over a target regi ...

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