2 mars 2015

Chaleur d'un impact météoritique

La comète qui a frappé la Terre de plein fouet et qui a exterminé les dinosaures, les ptérosaures et les reptiles marins il y a 65 millions d'années a eu des effets dévastateurs sur l'environnement global. Toutefois, malgré qu'elle ait frappé au Mexique, certains avancent la théorie selon laquelle les effets de l'intense chaleur auraient été plus dévastateurs de l'autre côté du globe qu'ici, en Amérique.

Extrait de l'article:

The space rock that struck Mexico's Yucatan peninsula at the end of the Cretaceous period seems to have ultimately wiped out the dinosaurs. But did it ignite global firestorms that destroyed almost everything at unthinkable speed?

A bit of playing with fire shows that the reality may be more complicated than we thought.

The small-scale inferno pictured is created by four halogen lamps. The idea is to recreate the immense thermal energy that would have been released at the impact site.

Claire Belcher of the University of Exeter, UK, and her colleagues placed the lamps around a basket of plant material, such as the pine tree needles shown here, to see how living and dead vegetation would be affected by this heat.

The researchers found that close to the Chicxulub impact site, even the most severe heat pulse predicted by computer simulations would have lasted less than a minute, which was too short to ignite live plants. However, less-intense heat would have been felt as far away as New Zealand and lasted about 7 minutes – long enough to start live vegetation burning.

"This flips our understanding of the effects of the impact on its head," says Belcher. "Palaeontologists may need to look for new clues from fossils found a long way from the impact to better understand the mass extinction event."

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