Feralia Planitia

Feralia Planitia
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Feralia Planitia (green and blue, center), an old, degraded crater near Vesta's equator. It is 270 km across and predates Rheasilvia (green at bottom)
Feature typePlains, impact basin
Location4 Vesta
Coordinates3°2′N 101°43′E / 3.033°N 101.717°E / 3.033; 101.717[1]
Length270 km (170 mi)[1]
Depth5–7 km (3.1–4.3 mi) (northern rim) 14 km (8.7 mi) (southern rim)[2]: 110 
DiscovererHubble Space Telescope
EponymFeralia

Feralia Planitia (/fəˈreɪliə pləˈnɪʃiə/) is the third-largest known impact structure on the asteroid Vesta, after Rheasilvia and Veneneia. It is one of several old, degraded impact basins that predate the Rheasilvia basin that now dominates Vesta. It is situated near the equator, and is 270 kilometres (170 mi) across east to west, though compressed latitudinally by the Rheasilvia impact.[3]

Observation and naming

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Feralia Planitia (green, top) is large enough to be visible from Earth, here as seen in a model of Vesta constructed from Hubble Space Telescope images taken in May 1996. The much larger crater at the bottom is Rheasilvia

Feralia Planitia was first seen in distant observations of Vesta by the Hubble Space Telescope (HST), which observed Vesta in 1994, 1996, 2007, and 2010. Feralia Planitia was then given the informal provisional designation of Feature Y.[4]: 1106, 1111  Feralia Planitia, alongside Vesta's other surface features, were resolved in detail for the first time by the Dawn orbiter, which orbited Vesta from 16 July 2011 to 4 September 2012.[5][6] The feature was then named after the ancient Roman public festival of Feralia, where citizens would place offerings at the tombs of the dead. The name Feralia Planitia was officially approved by the International Astronomical Union (IAU) on 27 December 2011.[1]

Geology and characteristics

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An image of the Lepida Quadrangle on Vesta, including the far northwestern corner of Feralia Planitia. Lepida is located at right, whilst Vestalia Terra is located at lower left

Feralia Planitia, located near the equator, dominates Vesta's eastern hemisphere. The basin is roughly ellipsoidal and elongated east to west and very roughly spans 130 by 300 kilometers. Feralia Planitia is surrounded by elevated terrain, with the northern rim dropping roughly 5–7 kilometers and the southern rim dropping by up to 14 kilometers. It borders the cratered highlands of Vestalia Terra to the west, the rim of Rheasilvia to the south, Divalia Fossae to the east, and Saturnalia Fossae to the northwest. Two major impact craters further alter Feralia Planitia's rim: the ~45 km Lepida on the northern wall, and the ~35–40 km Oppia on the southern wall.[2]: 107–112 

Feralia Planitia is likely an ancient, degraded impact basin, though whether it was formed by a single impact event or multiple remains unclear.[7]: 91 [2]: 116  The surrounding cratered highlands likely represent ejecta blasted out by the impact event(s) that created Feralia Planitia. Meanwhile, he interior of Feralia Planitia is comparatively unmodified by the extensive troughs of Divalia Fossae and Saturnalia Fossae, though some of their troughs extend into the walls of Feralia Planitia, indicating that they are younger than the basin. As Divalia Fossae and Saturnalia Fossae are similar in age to the Rheasilvia and Veneneia impact basins,[8] this indicates that both the trough systems and the two major southern impact basins are younger than Feralia Planitia.[2]: 116–118  However, a precise date for Feralia Planitia's formation cannot be determined through crater counting, as the basin underwent a resurfacing event roughly 3.62 billion years ago.[7]: 99  Feralia Planitia's surface is partially composed of eucrites, a type of basaltic rock containing anorthite, calcium-poor pyroxene, and augite. This is in contrast to the older northern and northeastern highlands, whose mineralogy is dominated by howardite, a mixture of eucrite and diogenite.[9]: 131–134  Feralia Planitia is the site of a negative gravity anomaly.[10]

References

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  1. ^ a b c "Feralia Planitia". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program. (Center Latitude: 3.03°, Center Longitude: 101.71°; Planetocentric, East+)
  2. ^ a b c d Garry, W. Brent; Williams, David A.; Yingst, R. Aileen; et al. (8 October 2014). "Geologic mapping of ejecta deposits in Oppia Quadrangle, Asteroid (4) Vesta". Icarus. 244: 104–119. Bibcode:2014Icar..244..104G. doi:10.1016/j.icarus.2014.08.046. hdl:2286/R.I.28056.
  3. ^ Garry, W. B.; et al. (April 2012). Geologic Mapping of Av-10 Oppia Quadrangle of Asteroid 4 Vesta (PDF). EGU General Assembly 2012. Vienna, Austria. Bibcode:2012EGUGA..14.5711G. 5711. Archived (PDF) from the original on 17 April 2021. Retrieved 21 May 2024.
  4. ^ Reddy, Vishnu; Li, Jian-Yang; Le Corre, Lucille; et al. (30 July 2013). "Comparing Dawn, Hubble Space Telescope, and ground-based interpretations of (4) Vesta". Icarus. 226 (1): 1103–1114. arXiv:1307.6608. Bibcode:2013Icar..226.1103R. doi:10.1016/j.icarus.2013.07.019.
  5. ^ Vega, Priscilla; Brown, Dwayne (16 July 2011). "NASA's Dawn Spacecraft Enters Orbit Around Asteroid Vesta". NASA. Archived from the original on 19 June 2012. Retrieved 17 July 2011.
  6. ^ "Dawn has Departed the Giant Asteroid Vesta". NASA JPL. NASA. 5 September 2012. Retrieved 5 September 2012.
  7. ^ a b Buczkowski, D. L.; Wyrick, D. Y.; Toplis, M. (4 April 2014). "The unique geomorphology and physical properties of the Vestalia Terra plateau". Icarus. 244: 89–103. Bibcode:2014Icar..244...89B. doi:10.1016/j.icarus.2014.03.035. hdl:2286/R.I.28072.
  8. ^ 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.
  9. ^ Tosi, F.; Frigeri, A.; Combe, J. -Ph (21 May 2015). "Mineralogical analysis of the Oppia quadrangle of asteroid (4) Vesta: Evidence for occurrence of moderate-reflectance hydrated minerals". Icarus. 259: 129–149. Bibcode:2015Icar..259..129T. doi:10.1016/j.icarus.2015.05.018.
  10. ^ Raymond, C. A.; Park, R. S.; Konopliv, A. S.; et al. (March 2014). Geophysical Constraints on the Structure and Evolution of Vesta's Crust and Mantle (PDF). 45th Lunar and Planetary Science Conference. The Woodlands, Texas, United States. 2214. Archived (PDF) from the original on 21 April 2024. Retrieved 21 May 2024.
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