Arachnoid (astrogeology)

Short description: Large structure of unknown origin on Venus

Venusian arachnoid Trotula Corona[1]

In astrogeology, an arachnoid /əˈræknɔɪd/ is a large geological structure resembling a spider web. They are of unknown origin, and have been found only on the surface of the planet Venus. They appear as concentric ovals surrounded by a complex network of fractures, and can span 200 kilometers. Over 90 arachnoids have been identified on Venus.[2]

Arachnoids could be related to volcanos, however it is also possible that different arachnoids are formed by different processes.[3] One possible explanation is that an upwelling of magma from the interior of the planet pushed up on the surface, causing cracks.[4] An alternate theory concerning their origin is that they are a precursor to coronae formation.[5]

Much of what is known about arachnoids is the result of studies performed by C.B. Dawson and L.S. Crumpler.[6]

## See also

* Chaos terrain
* Geysers on Mars
* Pancake dome
* Rille
* Coronae

## References

1. ↑ "Planetary Names: Corona, coronae: Trotula Corona on Venus". http://planetarynames.wr.usgs.gov/Feature/6092.
2. ↑ Kostama, V.P. (2002). "The Four Arachnoid Groups of Venus". Lunar and Planetary Science Conference: 1115. Bibcode: 2002LPI....33.1115K. http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1115.pdf.
3. ↑ This article contains text from the Astronomy Picture of the Day [1]. As a work of the United States Federal Government, it is in the public domain.
4. ↑ "WTP: Venus: Arachnoids". https://pds.jpl.nasa.gov/planets/captions/venus/arach.htm.
5. ↑ Hamilton, Calvin J.. "Arachnoids". http://solarviews.com/cap/venus/arach1.htm.
6. ↑ Dawson and Crumpler. "Characteristics of Arachnoids from Magellan Data". Lunar and Planetary Institute Conference: 383–384. http://www.lpi.usra.edu/meetings/lpsc1993/pdf/1193.pdf.

## External links

* NASA Astronomy Picture of the Day: Arachnoids on Venus (20 January 1998)

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