Divalia Fossae

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Divalia Fossae
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A section of Divalia Fossae between 45°E and 90°E
Feature typeTrough system
LocationEquator of 4 Vesta
Coordinates9°3′S 196°14′E / 9.050°S 196.233°E / -9.050; 196.233[1]
Length549.37 km[1]
DiscovererDawn
EponymDivalia

Divalia Fossae /dɪˈveɪliə ˈfɒseɪ/ is the large series of parallel equatorial troughs on the giant asteroid 4 Vesta. It is one of the longest chasms in the Solar System, stretching across roughly two-thirds of Vesta's equator. The trough system is named after the Roman festival of Divalia; the name Divalia Fossae was officially approved by the International Astronomical Union (IAU) on 27 December 2011.[1]

Geology

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Divalia Fossae is one of Vesta's two major trough systems, with the other being Saturnalia Fossae. Divalia Fossae consists of numerous—in some regions, up to seven—parallel troughs ranging from a few hundred meters to about 20.5 kilometers in diameter. The troughs run roughly parallel to Vesta's equator, encircling roughly two-thirds of the body. Divalia Fossae terminates at the cratered highlands of Vestalia Terra. Divalia Fossae in turn overlaps the troughs of Saturnalia Fossae, meaning that Divalia Fossae is the younger of the two trough systems; in 2021, a team of planetary scientists led by H. C. J. Cheng used crater counting to estimate Divalia Fossae's age as roughly 3.4–3.6 billion years old.[2][3]

The troughs of Divalia Fossae appear to run concentrically around the Rheasilvia impact basin. As such, early hypotheses of the origin of Divalia Fossae have invoked the impact event that created Rheasilvia, with energy from the impact event shattering Vesta's crust and leading to normal faulting along its equator. Estimates of Divalia Fossae's age via crater counts agree with the age of the Rheasilvia basin, supporting a relationship between the two.[3] However, the troughs of Divalia Fossae are not truly concentric with respect to Rheasilvia's center. Furthermore, the northernmost of Divalia Fossae's troughs cross-cut sections of Rheasilvia's rim. As the formation of Rheasilvia spanned roughly 2–3 hours, and models of fracturing in Vesta's interior take place within only minutes, this implies that Divalia Fossae formed after the Rheasilvia impact event.[4] An alternative hypothesis invokes true polar wander after the Rheasilvia impact event, with the impact event additionally decreasing Vesta's rotational period. The reorientation and "spinning up" of Vesta is capable of inducing stresses across Vesta's equator whilst still remaining consistent with the observed characteristics of Divalia Fossae.[4][5] A second hypothesis instead proposes that Divalia Fossae represents a large series of crater chains (catenae) from the debris ejected by the formation of Rheasilvia.[6]

A section of Divalia Fossa (green horizontal band), with lesser parallel troughs to the north and south
A computer-generated view of a portion of Divalia Fossa

See also

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References

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  1. ^ a b c "Divalia Fossae". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program. (Center Latitude: -9.05°, Center Longitude: 196.23°; Planetocentric, +East)
  2. ^ Schäfer, Michael; Natheus, Andreas; Williams, David A.; et al. (December 2014). "Imprint of the Rheasilvia impact on Vesta – Geologic mapping of quadrangles Gegania and Lucaria". Icarus. 244: 60–73. Bibcode:2014Icar..244...60S. doi:10.1016/j.icarus.2014.06.026. hdl:2286/R.I.28060.
  3. ^ a b Cheng, Hui Ching Jupiter; Klimczak, Christian; Fassett, Caleb I. (September 2021). "Age relationships of large-scale troughs and impact basins on Vesta". Icarus. 366. Bibcode:2021Icar..36614512C. doi:10.1016/j.icarus.2021.114512. 114512.
  4. ^ a b Cheng, Hui Ching Jupiter; Klimczak, Christian (August 2022). "Structural relationships in and around the Rheasilvia basin on Vesta". Journal of Structural Geology. 161. Bibcode:2022JSG...16104677C. doi:10.1016/j.jsg.2022.104677. 104677.
  5. ^ Schmidt, B. E. (December 2011). Tectonics of Vesta: Indication of Spin-up and Reorientation?. American Geophysical Union, Fall Meeting 2011. Bibcode:2011AGUFM.U21B..06S. U21B-06.
  6. ^ Hirata, Naoyuki (March 2023). "Secondary Cratering From Rheasilvia as the Possible Origin of Vesta's Equatorial Troughs". Journal of Geophysical Research: Planets. 128 (3). arXiv:2303.14955. Bibcode:2023JGRE..12807473H. doi:10.1029/2022JE007473. e2022JE007473.
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