THE IMPORTANCE OF THE ALVAREZ K-PG BOUNDARY ASTEROID IMPACT HYPOTHESIS FOR IMPACT CRATERING RESEARCH

When a granular material is impacted by a sphere, its surface deforms like a liquid yet it preserves a circular crater like a solid. Although the mechanism of granular impact cratering by solid spheres is well explored, our knowledge on granular impact cratering by liquid drops is still very limited. Here, by combining high-speed photography with high-precision laser profilometry, we investigate liquid-drop impact dynamics on granular surface and monitor the morphology of resulting impact craters. Surprisingly, we find that despite the enormous energy and length difference, granular impact cratering by liquid drops follows the same energy scaling and reproduces the same crater morphology as that of asteroid impact craters. Inspired by this similarity, we integrate the physical insight from planetary sciences, the liquid marble model from fluid mechanics, and the concept of jamming transition from granular physics into a simple theoretical framework that quantitatively describes all of the main features of liquid-drop imprints in granular media. Our study sheds light on the mechanisms governing raindrop impacts on granular surfaces and reveals a remarkable analogy between familiar phenomena of raining and catastrophic asteroid strikes.

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Australian impact cratering record: Updates and recent discoveries

Large Meteorite Impacts and Planetary Evolution VI ◽

10.1130/2021.2550(02) ◽

2021 ◽

Author(s):

Raiza R. Quintero ◽

Aaron J. Cavosie ◽

Morgan A. Cox ◽

Katarina Miljković ◽

Allison Dugdale

Keyword(s):

First Generation ◽

Ore Deposits ◽

Impact Cratering ◽

Accessory Minerals ◽

Asteroid Impact ◽

Shock Deformation ◽

Structure Recognition ◽

Deformation Phase ◽

Oblique Impacts

ABSTRACT There are currently 31 confirmed structures of impact origin in Australia. More than 49 additional structures have been proposed to have formed due to asteroid impact but await confirmation. Many discoveries have been made in Australia in the time since the last comprehensive review of the Australian impact cratering record was published in a peer-reviewed journal in 2005. These include further expanding the record of confirmed craters, and providing new insights into a variety of impact-related processes, such as shock deformation, phase transitions in accessory minerals, new impact age determinations, studies of oblique impacts, and more. This update is a review that focuses principally on summarizing discoveries made since 2005. Highlights since then include confirmation of five new Australian impact structures, identification of Earth’s oldest recognized impact structure, recognition of shock deformation in accessory minerals, discovery of the high-pressure phase reidite in Australia, determination of the links between impact craters and some ore deposits, and publication of the first generation of numerical hydrocode models for some Australian craters.

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The demise of dinosaurs and learned taste aversions: The biotic revenge hypothesis

Ideas in Ecology and Evolution ◽

10.4033/iee.2017.10.9.c ◽

2018 ◽

Vol 10 (1) ◽

Author(s):

Michael Frederick ◽

Gordon G. Gallup, Jr.

Keyword(s):

Empirical Support ◽

Volcanic Eruptions ◽

Deccan Traps ◽

Supporting Evidence ◽

Asteroid Impact ◽

Toxic Plants ◽

Extinction Event ◽

Impact Hypothesis ◽

Multiple Causes

Numerous hypotheses have been advanced to explain the worldwide extinction event that led to the disappearance of the dinosaurs. There is considerable empirical support for the well-known asteroid impact hypothesis, and volcanic eruptions in the Deccan Traps have also been implicated. Increasingly, theories involving multiple causes are being considered, yet few of these consider how the cognitive and behavioral abilities of certain classes of animals may have differed in ways that allowed some to survive while others perished. Here we advance the hypothesis along with supporting evidence that the emergence of toxic plants coupled with an inability to form learned taste aversions may have contributed to the extinction of dinosaurs.

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Premature rejection in science: The case of the Younger Dryas Impact Hypothesis

Science Progress ◽

10.1177/00368504211064272 ◽

2022 ◽

Vol 105 (1) ◽

pp. 003685042110642

Author(s):

James Lawrence Powell

Keyword(s):

Continental Drift ◽

Younger Dryas ◽

Western Hemisphere ◽

First Century ◽

Meteorite Impact ◽

Substantial Evidence ◽

Indian Culture ◽

Impact Cratering ◽

Cool Period ◽

Impact Hypothesis

The progress of science has sometimes been unjustifiably delayed by the premature rejection of a hypothesis for which substantial evidence existed and which later achieved consensus. Continental drift, meteorite impact cratering, and anthropogenic global warming are examples from the first half of the twentieth century. This article presents evidence that the Younger Dryas Impact Hypothesis (YDIH) is a twenty-first century case. The hypothesis proposes that the airburst or impact of a comet ∼12,850 years ago caused the ensuing ∼1200-year-long Younger Dryas (YD) cool period and contributed to the extinction of the Pleistocene megafauna in the Western Hemisphere and the disappearance of the Clovis Paleo-Indian culture. Soon after publication, a few scientists reported that they were unable to replicate the critical evidence and the scientific community at large came to reject the hypothesis. By today, however, many independent studies have reproduced that evidence at dozens of YD sites. This article examines why scientists so readily accepted the early false claims of irreproducibility and what lessons the premature rejection of the YDIH holds for science.

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Origins of the asteroid-impact hypothesis

Physics Today ◽

10.1063/pt.3.4764 ◽

2021 ◽

Vol 74 (6) ◽

pp. 12-12

Author(s):

Nicholas R. White

Keyword(s):

Asteroid Impact ◽

Impact Hypothesis

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The demise of dinosaurs and learned taste aversions: The biotic revenge hypothesis

Ideas in Ecology and Evolution ◽

10.24908/iee.2017.10.9.c ◽

2018 ◽

Vol 10 (1) ◽

Author(s):

Michael Frederick ◽

Gordon G. Gallup, Jr.

Keyword(s):

Empirical Support ◽

Volcanic Eruptions ◽

Deccan Traps ◽

Supporting Evidence ◽

Asteroid Impact ◽

Toxic Plants ◽

Extinction Event ◽

Impact Hypothesis ◽

Multiple Causes

Numerous hypotheses have been advanced to explain the worldwide extinction event that led to the disappearance of the dinosaurs. There is considerable empirical support for the well-known asteroid impact hypothesis, and volcanic eruptions in the Deccan Traps have also been implicated. Increasingly, theories involving multiple causes are being considered, yet few of these consider how the cognitive and behavioral abilities of certain classes of animals may have differed in ways that allowed some to survive while others perished. Here we advance the hypothesis along with supporting evidence that the emergence of toxic plants coupled with an inability to form learned taste aversions may have contributed to the extinction of dinosaurs.

Download Full-text