A model for long-term climatic effects of impacts

We simulated climatic changes following the impacts of asteroids of different sizes on the present surface of Earth. These changes are assumed to be due to the variations of the radiation energy budget as determined by the amount of dust globally distributed in the atmosphere following the impact. A dust evolution model is used to determine the dust particle size spectra as a function of time and atmospheric altitude. We simulate radiation transfer through the dust layer using a multiple scattering calculation scheme and couple the radiative fluxes to an ocean circulation model in order to determine climatic changes and deviations over 2000 years following the impact. Resulting drops in sea surface temperatures are of the order of several degrees at the equator and decrease toward the poles, which is deduced from the increasing importance of infrared insulation of the dust cover at high latitudes. While gravitational settling reduces the atmospheric amount of dust significantly within 6 months, temperature changes remain present for roughly 1 year irrespective of impactor size. Below 1000 m ocean depth, these changes are small, and we do not observe significant modifications in the structure of the ocean circulation pattern. For bodies smaller than 3 km in diameter, climatic effects increase with impactor size. Beyond this threshold, there is enough dust in the atmosphere to block almost completely solar radiation; thus additional dust does not enhance climatic deviations anymore. In fact, owing to interaction in the infrared, we even observe smaller effects by going from a 5 km impactor to larger diameters

The Atmospheric Effects Model (AEM): Estimating Projectile Survivability for Crater Formation on Venus, Earth, and Mars

The Atmospheric Effects Model (AEM) described here is a modular tool to investigate the evolution of projectile (asteroid and meteoroid) characteristics through an atmosphere to approximate the likelihood of impact crater formation. Using AEM, I examine the effects of deceleration, mass loss, and fragmentation on a theoretical projectile population through the atmospheres of Venus, Earth, and Mars. Projectiles were modeled to span densities, diameters, velocities, and angles of trajectory. Algorithms and parameters were optimized using known terrestrial impacts (Chicxulub and Meteor Crater) and observed meteor phenomena (Tunguska airburst and Chelyabinsk bolide). I show that planetary atmospheres effectively filter small projectiles, and that variations in algorithms and parameters produce reasonable results when applied correctly. Projectiles required to produce a crater ≥ 1 km have initial masses ≥ 10^6 kg for Mars, ≥ 10^8 kg for Earth, and ≥ 10^10 kg for Venus. Applications include surface age and analytical error constraints.Master of Scienc

Catastrophic events & mass extinctions, impacts and beyond

sponsors University of Vienna, Austria, Lunar and Planetary Institute ... [and others]international organizing and program committee, Walter Alvarez ... [and others] ; local organizing committee, Christian Koeberl ... [and others]PARTIAL CONTENTS: Global Distribution of Chicxulub Ejecta / P. Claeys, W. Kiessling, and W. Alvarez--Long-Term Environmental Perturbations Following a Late Eocene Impact? Evidence from the Massignano GSSP, Italy / R. Coccioni, D. Basso, H. Brinkhuis, S. Galeotti, S. Gardin, S. Monechi, and S. SpezzaJerri--Radio Search for Extrasolar Cometary Impacts at 22 GHz (Water MASER Emission) / C.B. Cosmovici, S. Pogrebenko, S. Montebugnoli, and G. Maccaferri--Comparison of the Chemical Composition Between Bosumtwi Rocks and Ivory Coast Tektites: Search for a Meteoritic Component in Impact Breccias / X. Dai, C. Koeberl, W.U. Reimold, and I. McDonal

Impact cratering, bridging the gap between modeling and observations : February 7-9, 2003, Houston, Texas

The purpose of this workshop is to discuss how physical observations of craters, both on the Earth and on other solid bodies of the solar system, can be combined with the results from modeling of impact cratering for a better understanding of the impact cratering process. The main goals of the workshop are to reconcile physical observations with theoretical and experimental modeling of impact processes, and to point out areas that future studies should focus on to improve the observation/modeling connection.Sponsor: Lunar and Planetary Institute, National Aeronautics and Space AdministrationSponsor: Lunar and Planetary Institute, National Aeronautics and Space Administration, Conveners: Robert Herrick. Lunar and Planetary Institute, Elisabetta Pierrazzo, Planetary Science Institute ; Scientific Organizing Committee: Bevan French, Natural History Museum, Kevin Housen, Boeing Corporation, William McKinnon, Washington University, Jay Melosh, University of Arizona, Michael Zolensky, NASA Johnson Space Center.Modeling Meteorite Impacts: What We Know and What We Would Like to Know / H.J. Melosh--Observations of the Terrestrial Impact Cratering Record / R. A. F. Grieve--What Do We Need to Know to Model Impact Processes? / K. A. Holsapple--Mechanisms of In Situ Rock Displacement During Hypervelocity Impact:Field and Microscopic Observations / J. G. Spray--Effects of Target Properties on the Cratering Process / K. R. Housen--Importance of Target Properties on Planetary Impact Craters, Both Simple and Complex / P. M. Schenk

Modeling the formation of the K-P boundary layer

Accepted versio

Large Meteorite Impacts and Planetary Evolution

Topics considered include: Petrography, geochemistry and geochronology; impact-induced hydrothermal base metal mineralization; nickel-and platinum group element -enriched quartz norite in the latest jurassic morokweng impact structure, south Africa; extraterrestrial helium trapped in fullerenes in the sudbury; synthetic aperture radar characteristics of a glacially modified meltsheet; the chicxulub seismic experiment; chemical compositions of chicxulub impact breccias; experimental investigation of the chemistry of vaporization of targets in relation to the chicxulub impact; artificial ozone hole generation following a large meteoroid impact into an oceanic site; three dimensional modeling of impactite bodies of popigai impact crater, Russia

Results of the Workshop on Impact Cratering, Bridging the Gap Between Modeling and Observations : February 7-9, 2003, Houston, Texas

Discusses how physical observations of craters, both on the Earth and on other solid bodies of the solar system, can be combined with the results from modeling of impact cratering for a better understanding of the impact cratering process.Sponsored by: Lunar and Planetary Institute, National Aeronautics and Space AdministrationEdited by: Robert Herrick and Elisabetta Pierazzo ; Sponsored by: Lunar and Planetary Institute, National Aeronautics and Space Administration ; Scientific Organizing Committee: Bevan French, Natural History Museum, Kevin Housen, Boeing Corporation, William McKinnon, Washington University, Jay Melosh, University of Arizona, Michael Zolensky, NASA Johnson Space Center.PARTIAL CONTENTS: Observations of the Terrestrial Impact Cratering Record / R. A. F. Grieve--Antipodal Hotspots on Earth: Are Major Deep-Ocean Impacts the Cause? / J. T. Hagstrum--Magnetic Fields of Lunar Impact Basins and Their Use in Constraining the Impact Process / J. S. Halekas and R. P. Lin--Pyroclastic Flows and Surges: Possible Analogy for Crater Ejecta Deposition / H. Hargitai and A. Kereszturi--Thicknesses of and Primary Ejecta Fractions in Basin Ejecta Deposits / L. A. Haskin and W. B. McKinnon--Constraints on the Impact Process from Observations of Oblique Impacts on the Terrestrial Planets / R. R. Herrick and K. Hessen--Linking Experimental Modelling of Impact Craters to Structural Components of the Real Thing / A. R. Hildebrand--Does Melt Volume Give the Signature of the Impactor? / K. A. Holsapple--What Do We Need to Know to Model Impact Processes? / K. A. Holsapple--Effects of Target Properties on the Cratering Process / K. R. Housen--Complex Crater Formation: Verification of Numerical Models / B. A. Ivanov

On impact and volcanism across the Cretaceous-Paleogene boundary

The cause of the end-Cretaceous mass extinction is vigorously debated, owing to the occurrence of a very large bolide impact and flood basalt volcanism near the boundary. Disentangling their relative importance is complicated by uncertainty regarding kill mechanisms and the relative timing of volcanogenic outgassing, impact, and extinction. We used carbon cycle modeling and paleotemperature records to constrain the timing of volcanogenic outgassing. We found support for major outgassing beginning and ending distinctly before the impact, with only the impact coinciding with mass extinction and biologically amplified carbon cycle change. Our models show that these extinction-related carbon cycle changes would have allowed the ocean to absorb massive amounts of carbon dioxide, thus limiting the global warming otherwise expected from postextinction volcanism

NEOimpactor: a tool for assessing Earth's vulnerability to the NEO impact hazard

The Earth’s surface bears the scars of 4.5 billion years of bombardment by asteroids,despite most having been erased by tectonic activity and erosion. Asteroids predominantlyorbit the Sun in the asteroid belt between Mars and Jupiter, but a large numberoccupy orbits close to the Earth’s. These bodies are termed Near Earth Objects (NEOs)and they present a very real impact threat to the Earth. In 1998 NASA inauguratedthe ‘Spaceguard Survey’ to catalogue 90% of NEOs greater than 1 km in diameter. Thesmaller bodies, meanwhile, remain undetected and far more numerous.In order to understand the NEO hazard, the consequences resulting from an asteroidimpact require modelling. While the atmospheric entry of asteroids is a criticalpart of the impact process, it is the surface impact which is most important, both ontoland and into the oceans. It is the impact generated effects (IGEs) that are hazardousto human populations on the Earth and the infrastructure they occupy. By modellingthese IGEs and the consequences they present for humans and infrastructure, anunderstanding of the global vulnerability to the hazard is developed.‘NEOimpactor’ is the software solution built to investigate the global vulnerabilityto NEO impacts. By combining existing mathematical models which describethe impact and effects, a unified impact simulator tool has been developed with thecapacity to model the real consequences of any terrestrial impact.By comparing the consequences of multiple impact events, a complete vulnerabilityassessment of the global NEO hazard is derived. The result maps are designedfor ease of dissemination to explain the impact risk to a non-specialist audience. Thesystem has identified China, US, India, Japan and Brazil as facing the greatest overallrisk, as well as indicating the various factors influencing vulnerability. The results canbe used for informing the international decision making processes regarding the NEOhazard and potential mitigation strategies

Impactors and the Impacted: Analytical Techniques to Identify and Understand the Impact Evolution of Extraterrestrial Materials

Impacts play a huge role in Solar System evolution. Signatures of the early phases of planetary compaction were identified in meteorites, which implied impacts were the driver for asteroid compaction. Traces of impacting projectiles have also been located at sites all over the world in impact ejecta layers. Here, ejecta from a catastrophic impact 65 Ma ago is examined to understand the process of global ejecta processing and dispersion