Southwest Research Institute | 2016 jun 22
[c][attachment=0]earth-asteroid-impact.jpg[/attachment][/c][hr][/hr]In the first billion years of Earth’s history, the planet was bombarded by primordial asteroids, while a faint Sun provided much less heat. A Southwest Research Institute-led team posits that this tumultuous beginning may have ultimately fostered life on Earth, particularly in terms of sustaining liquid water.
“The early impacts caused temporary, localized destruction and hostile conditions for life. But at the same time, they had a long-term beneficial effect in stabilizing surface temperatures and delivering key elements for life as we know it,” said Dr. Simone Marchi ...
“Atmospheric and surface conditions during the first billion years of Earth’s history are poorly understood due to the scarcity of geological and geochemical evidence,” said Marchi. However, ancient zircon crystals in sedimentary rocks provide evidence that our planet had liquid oceans, at least intermittently, during this earliest period. His team created a new model for impact-generated outgassing on the early Earth, showing how a resulting greenhouse effect could have counterbalanced the weak light from the infant Sun enough to sustain liquid water.
The findings could be key to understanding how life started on Earth despite the faint young Sun and havoc caused by collisions. Studies of other stars, as well as theoretical modeling, have shown that Sun-like stars begin their life about 20 to 30 percent fainter in visible wavelengths than the Sun is at present. They gradually increase in luminosity over time. ...
Massive Impact-induced Release of Carbon and Sulfur Gases in the Early Earth’s Atmosphere - S. Marchi et al
- Earth and Planetary Science Letters 449:96 (01 Sep 2016) DOI: 10.1016/j.epsl.2016.05.032