This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

14 May 2009

Article: "Asteroid impact may have gassed Earth"

From the article...

A burst of carbon monoxide triggered by an asteroid impact may have been a key factor in the mass extinction which saw off the dinosaurs 65 million years ago.

The claim comes from Japanese scientists who have simulated the impact that created the massive crater at Chicxulub on Mexico's Yucatán Peninsula.

The Chicxulub impact, which occurred around the end of the Cretaceous period and the beginning of the Tertiary (the K-T boundary), is thought to have blackened the skies with dust, blocking photosynthesis. The impact would also have triggered intense global firestorms, boosting the atmospheric concentration of the greenhouse gas carbon dioxide and warming the Earth.

But the shock of the impact may also have released significant amounts of greenhouse gasses by breaking down carbonate rocks such as calcite. Previous estimates have suggested that the Chicxulub impact could have released enough carbon dioxide from carbonate rocks at the site to cause a global warming of about 1-2 ºC.1,2

The Japanese team, led by Ko Kawaragi of the University of Tokyo, now suggest in Earth and Planetary Science Letters3 that the shocked carbonates would have released much more carbon monoxide than carbon dioxide, leading to a global warming of 2-5 °C for several years after the impact.

"Asteroid impact may have gassed Earth: Did dinosaur-killing space rock create enough carbon monoxide to trigger extreme global warming?"
Anjali Nayar
Nature Magazine
13 May 2009

Link: Nature News Article


Earth and Planetary Science Letters
Volume 282, Issues 1-4, 30 May 2009, Pages 56-64

"Direct measurements of chemical composition of shock-induced gases from calcite: an intense global warming after the Chicxulub impact due to the indirect greenhouse effect of carbon monoxide"
Ko Kawaragia, Yasuhito Sekinea, Corresponding Author Contact Information, E-mail The Corresponding Author, Toshihiko Kadonob, Seiji Sugitaa, Sohsuke Ohnoc, Ko Ishibashid, Kosuke Kurosawaa, Takafumi Matsuia and Susumu Ikedaa, aDepartment of Complexity Science and Engineering, Graduate School of Frontier Sciences, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8561, Japan, bInstitute of Laser Engineering Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan, cInstitute for Study of the Earth's Interior, Okayama University, 827 Yamada, Misasa, Tottori 682-0193, Japan, dDepartment of Earth and Planetary Science, Graduate School of Science, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8561, Japan

Shock-induced devolatilization in hypervelocity impacts has been considered to play important roles in the atmospheric evolution and mass extinctions in Earth's history. Although the chemical composition of shock-induced gas species from carbonate rocks has been considered as a key to understand the environmental change after the Chicxulub impact, it has not been investigated extensively before. Here, we conduct direct measurements of the chemical composition (CO/CO2) of shock-induced gas species from calcite (CaCO3) using both a laser gun system and an isotopic labeling technique. The CO/CO2 ratio of the shock-induced gas species from calcite is measured to be 2.02 ± 0.41, suggesting that gaseous CO has been dominant in the shock-induced gases in the Chicxulub impact. In order to evaluate the environmental effects of the injection of CO gas, we investigated the post-impact atmospheric chemistry by incorporating our experimental results into a tropospheric photochemical model. The results suggest that an intense (2–5 °C) global warming would have lasted for several years after a Chicxulub-size impact mainly due to the greenhouse effect of tropospheric O3, which is produced via photochemical reactions associated with CO gas. Such an intense global warming could have damaged the biosphere in the mass extinction at the Cretaceous–Paleogene (K–P) boundary.

Link: Earth and Planetary Science Letters Abstract Link

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