Research press release


Scientific Reports

Palaeontology: Asteroid impact location contributed to the extinction of dinosaurs



海保 邦夫(かいほ・くにお)と大島 長(おおしま・なが)は、地中に存在する炭化水素と硫酸塩の量に基づいて、仮想の小惑星衝突で生成する成層圏のすすと硫酸塩の量を計算した。20、200、500、1500、および2600テラグラム(Tg)という5段階の量のブラックカーボン(すすに相当)を用いて、小惑星の衝突が生じる気候への影響を推定した。その結果、炭化水素濃度が高い、または極めて高い地帯(成層圏へ入るブラックカーボン230~590 Tgおよび590~2300 Tgに相当)では、世界の平均地表気温の低下が大量絶滅を引き起こす条件を発生させるものとなることが分かった。しかし、炭化水素濃度がそれに満たなければ、大量絶滅は起こらないと考えられた。研究チームは、地表の約13%がこの大量絶滅を引き起こすための要件を満たすと計算している。

The asteroid impact that led to the demise of the dinosaurs would only have resulted in a mass extinction in areas rich in hydrocarbons, occupying approximately 13% of the Earth’s surface, according to a study in Scientific Reports.

66 million years ago the Chicxulub asteroid impact, in what is now Mexico, led to an ecosystem collapse including the devastation of land vegetation, and the extinction of dinosaurs and approximately 75% of all land and sea animals. Previous research has shown that the burning of hydrocarbons in rocks as a result of the asteroid impact produced stratospheric soot and sulphate aerosols causing extreme global cooling and drought. However, the quantities of hydrocarbons and sulphur in rocks varies widely depending on the location, suggesting that the probability of an extinction event was dependent on the impact site.

Kunio Kaiho and Naga Oshima calculated the amount of stratospheric soot and sulphate that would be formed by a virtual asteroid impact, depending on the amount of hydrocarbon and sulphate present in the ground. Using five quantities of black carbon (equivalent to soot), 20, 200, 500, 1500, and 2600 teragrams (Tg), the authors estimated the effect on the climate caused by an asteroid impact. They found that in areas of the earth with a high or very high concentration of hydrocarbons (equivalent to 230-590 Tg of black carbon and 590-2,300 Tg of black carbon entering the stratosphere), the resulting decrease in global mean surface air temperature would produce the conditions responsible for a mass extinction. However, in areas with lower concentrations of hydrocarbons, a mass extinction would not have occurred. The authors calculate that approximately 13% of the earth’s surface meets the requirements that would have caused this mass extinction.

doi: 10.1038/s41598-017-14199-x

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