Wilkes Land crater

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Wilkes Land crater is an informal term that may apply to two separate cases of conjectured giant impact craters hidden beneath the ice cap of Wilkes Land, East Antarctica. These are distinguished by the names Wilkes Land anomaly and Wilkes Land mascon (mass concentration), based on terms used in their principal published reference sources.

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Wilkes Land anomaly

A giant impact crater beneath the Wilkes Land ice sheet was first proposed by Richard A. Schmidt in 1962 on the basis of the seismic and gravity discovery of the feature made by the U.S. Victoria Land Traverse in 1959–60 (VLT), and the data provided to Schmidt by John G. Weihaupt, geophysicist of the VLT (Geophysical Studies in Victoria Land, Antarctica, Report No. 1, Geophysical and Polar Research Center, University of Wisconsin, 1–123). [1] Schmidt further considered the possibility that it might be the elusive source of the tektites of the Australasian strewnfield (which is only 790,000 years old).

EGM2008 gravity anomaly map EGM2008 gravity anomaly map.svg
EGM2008 gravity anomaly map

The hypothesis was detailed in a paper by Weihaupt in 1976. [2] Evidence cited included a large negative gravity anomaly coincident with a subglacial topographic depression 243 kilometres (151 mi) across and having a minimum depth of 848 metres (2,782 ft).

The claims were challenged by Charles R. Bentley in 1979. [3] On the basis of a 2010 paper by Weihaupt et al., [4] Bentley's challenge was proven to be incorrect, and the Earth Impact Database (Rajmon 2011) reclassified the Wilkes Land Anomaly from a "possible impact crater" to a "probable impact crater" on that basis. A potential impact crater site has been proposed by other investigators in the Ross Sea. [5] [6]

Mass concentration

Map of Antarctica showing Wilkes Land, with the crater conjectured by von Frese et al. marked in red Antarctica Map Wilkes L Crater.png
Map of Antarctica showing Wilkes Land, with the crater conjectured by von Frese et al. marked in red

The Wilkes Land mass concentration (or mascon) is centered at 70°S120°E / 70°S 120°E / -70; 120 and was first reported at a conference in May 2006 by a team of researchers led by Ralph von Frese and Laramie Potts of Ohio State University. [7] [8]

The team used gravity measurements by NASA's GRACE satellites to identify a 300 km (190 mi) wide mass concentration and noted that this mass anomaly is centered within a larger ring-like structure visible in radar images of the land surface beneath the Antarctic ice cap. That combination suggested to them that the feature may mark the site of a 480 km (300 mi) wide impact crater buried beneath the ice and more than 2.5 times larger than the 180 km (110 mi) Chicxulub crater.

Due to the site's location beneath the Antarctic ice sheet, there are no direct samples to test for evidence of impact. There are alternative explanations for this mass concentration, such as formation by a mantle plume or other large-scale volcanic activity, but a variety of research methods lend support to the impact hypothesis. [9] If the impact crater hypothesis is correct, based on the size of the ring structure, it has been suggested by Frese's team that the impactor could have been four or five times wider than the Chicxulub impactor, which is believed to have caused the Cretaceous–Paleogene extinction event. [8]

Because mass concentrations on Earth are expected to dissipate over time, Frese and his collaborators believe the structure must be less than 500 million years old and also note that it appears to have been disturbed by the rift valley that formed 100 million years ago, during the separation of Australia from the Gondwana supercontinent. [8]

The researchers speculate that the putative impact and associated crater may have contributed to this separation by weakening the Earth's crust at this location. These bracketing dates also make it possible that the site could be associated with the Permian–Triassic extinction event. [8] The Permian–Triassic extinction occurred 250 million years ago and is believed to be the largest extinction event since the origin of complex multicellular life.

Plate reconstructions for the Permian–Triassic boundary place the putative crater directly antipodal to the Siberian Traps, and Frese et al. (2009) use the controversial theory that impacts can trigger massive volcanism at their antipodes to bolster their impact crater theory. [10] However, there are already other suggested candidates for giant impacts at the Permian–Triassic boundary, such as Bedout, off the northern coast of Western Australia, although all are equally contentious and it is currently under debate whether or not an impact played any role in this extinction.

The complete absence of a well-defined impact ejecta layer associated with the Permian–Triassic boundary at its outcrops within Victoria Land and the central Transantarctic Mountains argues against there having been any impact capable of creating a crater the size of the hypothesized Wilkes Land impact crater within Antarctica at the Permian–Triassic boundary. [11] [12] Nonetheless, according to Frese, recent studies in 2018 seem to sustain the impact origin of the crater, and the event may be linked to the separation of Eastern Antarctica from southern Australia. [13]

See also

Related Research Articles

<span class="mw-page-title-main">Extinction event</span> Widespread and rapid decrease in the biodiversity on Earth

An extinction event is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the background extinction rate and the rate of speciation. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from disagreement as to what constitutes a "major" extinction event, and the data chosen to measure past diversity.

The Mesozoic Era is the era of Earth's geological history, lasting from about 252 to 66 million years ago, comprising the Triassic, Jurassic and Cretaceous Periods. It is characterized by the dominance of gymnosperms such as cycads, ginkgoaceae and araucarian conifers, and of archosaurian reptiles such as the dinosaurs; a hot greenhouse climate; and the tectonic break-up of Pangaea. The Mesozoic is the middle of the three eras since complex life evolved: the Paleozoic, the Mesozoic, and the Cenozoic.

<span class="mw-page-title-main">Permian–Triassic extinction event</span> Earths most severe extinction event

Approximately 251.9 million years ago, the Permian–Triassicextinction event forms the boundary between the Permian and Triassic geologic periods, and with them the Paleozoic and Mesozoic eras. It is Earth's most severe known extinction event, with the extinction of 57% of biological families, 83% of genera, 81% of marine species and 70% of terrestrial vertebrate species. It is also the greatest known mass extinction of insects. It is the greatest of the "Big Five" mass extinctions of the Phanerozoic. There is evidence for one to three distinct pulses, or phases, of extinction.

<span class="mw-page-title-main">Triassic–Jurassic extinction event</span> Mass extinction ending the Triassic period

The Triassic–Jurassic (Tr-J) extinction event (TJME), often called the end-Triassic extinction, marks the boundary between the Triassic and Jurassic periods, 201.4 million years ago. It is one of five major extinction events, profoundly affecting life on land and in the oceans. In the seas, about 23–34% of marine genera disappeared. On land, all archosauromorph reptiles other than crocodylomorphs, dinosaurs, and pterosaurs became extinct; some of the groups which died out were previously abundant, such as aetosaurs, phytosaurs, and rauisuchids. Plants, crocodylomorphs, dinosaurs, pterosaurs and mammals were left largely untouched, allowing the dinosaurs, pterosaurs, and crocodylomorphs to become the dominant land animals for the next 135 million years.

<span class="mw-page-title-main">Chicxulub crater</span> Prehistoric impact crater in Mexico

The Chicxulub crater is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is offshore, but the crater is named after the onshore community of Chicxulub Pueblo. It was formed slightly over 66 million years ago when an asteroid, about ten kilometers in diameter, struck Earth. The crater is estimated to be 200 kilometers in diameter and 1 kilometer in depth. It is believed to be the second largest impact structure on Earth, and the only one whose peak ring is intact and directly accessible for scientific research.

<span class="mw-page-title-main">Mass concentration (astronomy)</span> Region of a planet or moons crust that contains a large positive gravitational anomaly

In astronomy, astrophysics and geophysics, a mass concentration is a region of a planet's or moon's crust that contains a large positive gravity anomaly. In general, the word "mascon" can be used as a noun to refer to an excess distribution of mass on or beneath the surface of an astronomical body, such as is found around Hawaii on Earth. However, this term is most often used to describe a geologic structure that has a positive gravitational anomaly associated with a feature that might otherwise have been expected to have a negative anomaly, such as the "mascon basins" on the Moon.

<span class="mw-page-title-main">Araguainha crater</span> Impact crater in Brazil

The Araguainha crater or Araguainha dome is an impact crater on the border of Mato Grosso and Goiás states, Brazil, between the villages of Araguainha and Ponte Branca. With a diameter of 40 kilometres (25 mi), it is the largest known impact crater in South America.

<span class="mw-page-title-main">Siberian Traps</span> Large region of volcanic rock in Russia

The Siberian Traps are a large region of volcanic rock, known as a large igneous province, in Siberia, Russia. The massive eruptive event that formed the traps is one of the largest known volcanic events in the last 500 million years.

<span class="mw-page-title-main">GRACE and GRACE-FO</span> Joint American-German space mission to map Earths gravitational field

The Gravity Recovery and Climate Experiment (GRACE) was a joint mission of NASA and the German Aerospace Center (DLR). Twin satellites took detailed measurements of Earth's gravity field anomalies from its launch in March 2002 to the end of its science mission in October 2017. The two satellites were sometimes called Tom and Jerry, a nod to the famous cartoon. The GRACE Follow-On (GRACE-FO) is a continuation of the mission on near-identical hardware, launched in May 2018. On March 19, 2024, NASA announced that the successor to GRACE-FO would be Gravity Recovery and Climate Experiment-Continuity (GRACE-C), to be launched in or after 2028.

<span class="mw-page-title-main">Silverpit crater</span>

Silverpit crater is a buried sub-sea structure under the North Sea off the coast of the island of Great Britain. The 20 km (12 mi) crater-like form, named after the Silver Pit—a nearby sea-floor valley recognized by generations of fishermen—was discovered during the routine analysis of seismic data collected during exploration for gas in the Southern North Sea Sedimentary Basin.

Ralph R. B. von Frese is an American geophysicist at the Ohio State University who identified the Wilkes Land mass concentration in Antarctica in collaboration with Laramie Potts.

Laramie Potts is an American scientist who identified the Wilkes Land mass concentration in Antarctica in collaboration with Ralph von Frese. He is from South Africa. He is an associate professor in the School of Applied Engineering and Technology and teaches geomatics (surveying) at the New Jersey Institute of Technology (NJIT).

<span class="mw-page-title-main">Cretaceous–Paleogene boundary</span> Geological boundary between time periods

The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K–T) boundary, is a geological signature, usually a thin band of rock containing much more iridium than other bands. The K–Pg boundary marks the end of the Cretaceous Period, the last period of the Mesozoic Era, and marks the beginning of the Paleogene Period, the first period of the Cenozoic Era. Its age is usually estimated at 66 million years, with radiometric dating yielding a more precise age of 66.043 ± 0.043 Ma.

<span class="mw-page-title-main">Gondwana</span> Neoproterozoic to Cretaceous landmass

Gondwana was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia, Zealandia, Arabia, and the Indian Subcontinent.

<span class="mw-page-title-main">Cretaceous–Paleogene extinction event</span> Mass extinction event about 66 million years ago

The Cretaceous–Paleogene (K–Pg) extinction event, also known as the K–T extinction, was the mass extinction of three-quarters of the plant and animal species on Earth approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs. Most other tetrapods weighing more than 25 kg (55 lb) also became extinct, with the exception of some ectothermic species such as sea turtles and crocodilians. It marked the end of the Cretaceous period, and with it the Mesozoic era, while heralding the beginning of the current era, the Cenozoic. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, Fatkito boundary or K–T boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows unusually high levels of the metal iridium, which is more common in asteroids than in the Earth's crust.

<span class="mw-page-title-main">Michael R. Rampino</span> American geologist

Michael R. Rampino is a Geologist and Professor of Biology and Environmental Studies at New York University, known for his scientific contributions on causes of mass extinctions of life. Along with colleagues, he's developed theories about periodic mass extinctions being strongly related to the earth's position in relation to the galaxy. "The solar system and its planets experience cataclysms every time they pass "up" or "down" through the plane of the disk-shaped galaxy." These ~30 million year cyclical breaks are an important factor in evolutionary theory, along with other longer 60-million- and 140-million-year cycles potentially caused by mantle plumes within the planet, opining "The Earth seems to have a pulse," He is also a research consultant at NASA's Goddard Institute for Space Studies (GISS) in New York City.

<span class="mw-page-title-main">Asish Basu</span> Indian geologist, academic, and researcher

Asish R. Basu is a geologist, academic, and researcher. He is Professor Emeritus of Earth and Environmental Sciences at the University of Texas at Arlington. He is most known for his research in Earth Science -related subjects, such as isotope geochemistry, flood basalt volcanism, and mineralogy-petrology.

References

  1. ↑ Schmidt, Richard A. (1962). "Australites and Antarctica". Science. 138 (3538): 443–444. Bibcode:1962Sci...138..443S. doi:10.1126/science.138.3538.443. PMID   17794921. S2CID   5626171. Abstract.
  2. ↑ Weihaupt, John G. (1976). "The Wilkes Land anomaly: Evidence for a possible hypervelocity impact crater". Journal of Geophysical Research. 81 (B32): 5651–5663. Bibcode:1976JGR....81.5651W. doi:10.1029/JB081i032p05651. Abstract.
  3. ↑ Bentley, Charles R. (September 10, 1979). "No giant meteorite crater in Wilkes Land, Antarctica". Journal of Geophysical Research. 84: 5681–5682. Bibcode:1979JGR....84.5681B. doi:10.1029/JB084iB10p05681. Abstract.
  4. ↑ Weihaupt, John G.; Rice, Alan; Van der Hoeven, Frans G. (2010). "Gravity anomalies of the Antarctic lithosphere". Lithosphere. 2 (6): 454–461. Bibcode:2010Lsphe...2..454W. doi: 10.1130/l116.1 . Abstract.
  5. ↑ Khryanina, L. P. (1985). "Possible meteorite impact structures in the Ross Sea, Antarctica". International Geology Review. 27 (10): 1207–1211. Bibcode:1985IGRv...27.1207K. doi:10.1080/00206818509466495. ISSN   0020-6814.
  6. ↑ Gerard-Little, P.; Abbott, D.; Breger, D.; Burckle, L. (2006-03-01). "Evidence for a Possible Late Pliocene Impact in the Ross Sea, Antarctica". 37th Annual Lunar and Planetary Science Conference 1399. Bibcode: 2006LPI....37.1399G .
  7. ↑ Frese, Ralph R. B. von; Potts, Laramie V.; Wells, Stuart B.; Gaya-Piqué, Luis-Ricardo; Golynsky, Alexander V.; Hernandez, Orlando; Kim, Jeong Woo; Kim, Hyung Rae; Hwang, Jong Sun (2006). "Permian–Triassic mascon in Antarctica". American Geophysical Union, Fall Meeting 2007. 2007: Abstract T41A–08. Bibcode:2006AGUSM.T41A..08V.
  8. 1 2 3 4 Gorder, Pam Frost (June 1, 2006). "Big Bang in Antarctica – Killer Crater Found Under Ice". Ohio State University Research News. Archived from the original on March 6, 2016.
  9. ↑ Klokočník, Jaroslav; Kostelecký, Jan; Bezděk, Aleš (17 August 2018). "On the detection of the Wilkes Land impact crater". Earth, Planets and Space. 70 (1): 135. Bibcode:2018EP&S...70..135K. doi: 10.1186/s40623-018-0904-7 . hdl: 10084/131644 . ISSN   1880-5981.
  10. ↑ Frese, Ralph R. B. von; Potts, Laramie V.; Wells, Stuart B.; Leftwich, Timothy E.; Kim, Hyung Rae; Kim, Jeong Woo; Golynsky, Alexander V.; Hernandez, Orlando; Gaya-Piqué, Luis-Ricardo (25 February 2009). "GRACE gravity evidence for an impact basin in Wilkes Land, Antarctica". Geochemistry, Geophysics, Geosystems. 10 (2). Bibcode:2009GGG....10.2014V. doi: 10.1029/2008GC002149 . ISSN   1525-2027.
  11. ↑ Retallack, Gregory J.; Seyedolali, Abbas; Krull, Evelyn S.; Holser, William T.; Ambers, Clifford P.; Kyte, Frank T. (1998). "Search for evidence of impact at the Permian–Triassic boundary in Antarctica and Australia". Geology. 26 (11): 979–982. Bibcode:1998Geo....26..979R. doi:10.1130/0091-7613(1998)026<0979:SFEOIA>2.3.CO;2.
  12. ↑ Retallack, Gregory J.; Greaver, Tara; Jahren, A. Hope (January 2007). "Return to Coalsack Bluff and the Permian–Triassic boundary in Antarctica". Global and Planetary Change. 55 (1–3): 90–108. Bibcode:2007GPC....55...90R. doi:10.1016/j.gloplacha.2006.06.017.
  13. ↑ Klokočník, Jaroslav; Kostelecký, Jan; Bezděk, Aleš (2018). "On the detection of the Wilkes Land impact crater". Earth Planets Space. 70: 135. Bibcode:2018EP&S...70..135K. doi: 10.1186/s40623-018-0904-7 . hdl: 10084/131644 .

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