Snowman craters

Marcia, Calpurnia, and Minucia
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The snowman craters. From left to right are Marcia, Calpurnia, and Minucia.
Feature typeImpact craters
Location4 Vesta
Coordinates
Diameter
  • 67.60 km (Marcia)
  • 50.19 km (Calpurnia)
  • 23.15 km (Minucia)
DiscovererDawn
EponymRoman Vestal Virgins

The snowman craters are a set of three overlapping craters on the giant asteroid 4 Vesta: Marcia, Calpurnia, and Minucia. The crater set lies in Vesta's northern hemisphere, spanning southwest to northeast from the equator to nearly 30°N. The craters formed sequentially, with the smallest and northernmost – Minucia – being the oldest, and the largest and southernmost – Marcia – being the youngest.

Naming

The crater set was given the nickname "snowman craters" by Dawn's imaging team due to its resemblance to snowman sculptures. The individual craters were all named after Vestal Virgins of ancient Roman religion; the names were all adopted by the International Astronomical Union in 2011. Marcia's name was adopted on 30 September, and Calpurnia and Minucia's names were adopted on 27 December.

Characteristics

The crater complex stretches southwest to northeast from Vesta's equator to nearly 30°N.: 20  A low-albedo region, informally named "Olbers" in Hubble Space Telescope images before Dawn's arrival, lies to the east.: 81  Marcia is the largest and southernmost of the three, Minucia the smallest and northernmost, and Calpurnia in between. The terrain surrounding the complex is softened and darkened by craters' ejecta blankets. Stratigraphically, the craters lie one on top of the other, with Minucia the oldest and Marcia the youngest.: 21 : 81  Initially, it was believed that Marcia and Minucia formed simultaneously from the impact of a binary asteroid's components.

Marcia

Marcia has a diameter of 67.6 km, spanning 68 km north to south and 58 km east to west.: 81  Its elongated shape suggests that it was formed by an oblique, low-angle impact.: 15  It is the largest well-preserved post-Rheasilvia crater and shows a complex geology.: 393  Its crater rim is irregular in the west and more rounded in shape in the east, with outcroppings of bright material.: 394  Its northern wall has gully-like features leading to lobate deposits near the bottom of the crater.: 402  The eastern crater wall is relatively steep. Part of its floor terrain has pits ranging in size from a few tens of meters to hundreds of meters. The pits are usually rimless and some appear in clusters. The origin of the pits are debated, but may be the result of the sublimation of volatiles. The southern part of the floor is elevated on a terrace, separated from the northern floor by a scarp. The southern floor is smoother in texture with lobes of material.: 397  Marcia's ejecta blanket is darker on its eastern side.: 399 

Calpurnia

Calpurnia has a diameter of 50.2 km, spanning 54 km north to south and 52 km east to west.: 81  It is about half as deep as Marcia.: 15  Its crater rim is less defined than Marcia's, and part of Marcia's ejecta blanket covers its floor and southwest rim.: 81  Calpurnia's ejecta is also dark and partially constrained by the Vestalia Terra highlands to the east. Most of its own ejecta field was obliterated by the Marcia impact.: 15 

Minucia

Minucia has a diameter of 23.2 km, spanning 26 km north to south and 23 km east to west.: 81  Its rim is not well-defined, and it has a lower than normal depth-to-diameter ratio compared to similarly-sized craters. Its floor has an oval-shaped lobate deposit, which may be from landslide material or impact melt.: 29 

References

  1. 1 2 3 4 5 6 7 8 Individual GPN entries:
    • For Marcia's, see "Marcia". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
    • For Calpurnia's, see "Calpurnia". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
    • For Minucia's, see "Minucia". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
    Coordinates are planetocentric, +East
  2. ↑ Denise Chow (3 August 2011). "Asteroid Vesta Home to 'Snowman' Made of Craters". NBC News. Retrieved 8 September 2026.
  3. ↑ "Vesta - Snowman Craters - NASA Science". May 2025. Archived from the original on 15 April 2026. Retrieved 8 September 2026.
  4. 1 2 Aileen Yingst, R.; Mest, Scott C.; Brent Garry, W.; Williams, David A.; Berman, Daniel C.; Gregg, Tracy K. P. (September 2023). "A Geologic Map of Vesta Produced Using a Hybrid Method for Incorporating Spectroscopic and Morphologic Data". The Planetary Science Journal. 4 (9): 157. Bibcode:2023PSJ.....4..157A. doi:10.3847/PSJ/acebe9. ISSN 2632-3338. Archived from the original on 14 March 2024. Retrieved 13 November 2026.
  5. 1 2 3 4 5 6 Williams, David A.; et al. (December 2014). "The geology of the Marcia quadrangle of asteroid Vesta: Assessing the effects of large, young craters". Icarus. 244: 74–88. Bibcode:2014Icar..244...74W. doi:10.1016/j.icarus.2014.01.033.
  6. ↑ Lakdawalla, Emily (16 August 2011). "Vesta's wacky craters". The Planetary Society. Archived from the original on 20 April 2026. Retrieved 18 October 2026.
  7. ↑ "3-D Image of Vesta's "Snowman" Craters". NASA Jet Propulsion Laboratory (JPL). 24 January 2012. Archived from the original on 10 May 2026. Retrieved 13 November 2026.
  8. 1 2 3 Jaumann, R.; Nass, A.; Otto, K.; Krohn, K.; Stephan, K.; McCord, T.B.; Williams, D.A.; Raymond, C.A.; Blewett, D.T.; Hiesinger, H.; Yingst, R.A.; De Sanctis, M.C.; Palomba, E.; Roatsch, T.; Matz, K.-D. (September 2014). "The geological nature of dark material on Vesta and implications for the subsurface structure". Icarus. 240: 3–19. Bibcode:2014Icar..240....3J. doi:10.1016/j.icarus.2014.04.035. Archived from the original on 2 June 2025. Retrieved 13 November 2026.
  9. 1 2 3 4 5 De Sanctis, M.C.; Frigeri, A.; Ammannito, E.; Tosi, F.; Marchi, S.; Zambon, F.; Raymond, C.A.; Russell, C.T. (March 2015). "Mineralogy of Marcia, the youngest large crater of Vesta: Character and distribution of pyroxenes and hydrated material". Icarus. 248: 392–406. Bibcode:2015Icar..248..392D. doi:10.1016/j.icarus.2014.10.051. Archived from the original on 15 April 2025. Retrieved 13 November 2026.
  10. ↑ "Topography and Albedo Image of Marcia Crater". NASA/Jet Propulsion Laboratory. 11 December 2011. Archived from the original on 19 April 2026. Retrieved 18 October 2026.
  11. ↑ Williams, David A.; O'Brien, David P.; Schenk, Paul M.; Denevi, Brett W.; Carsenty, Uri; Marchi, Simone; Scully, Jennifer E.C.; Jaumann, Ralf; De Sanctis, Maria Cristina; Palomba, Ernesto; Ammannito, Eleonora; Longobardo, Andrea; Magni, Gianfranco; Frigeri, Alessandro; Russell, Christopher T. (November 2014). "Lobate and flow-like features on asteroid Vesta". Planetary and Space Science. 103: 24–35. Bibcode:2014P&SS..103...24W. doi:10.1016/j.pss.2013.06.017. Archived from the original on 18 December 2024. Retrieved 13 November 2026.