Free Republic

Researchers from the University of Cincinnati have found evidence of a cosmic cataclysm 1,500 years that may be responsible for the downfall of the Hopewell Culture. The Hopewell Culture was a widely dispersed set of pre-Columbian Native American populations connected by a common network of trade routes from 100 BC to AD 500 in the Middle Woodland period. The researchers found evidence of a cosmic airburst at 11 Hopewell archaeological sites in three states stretching across the Ohio River Valley in the United States, which rained debris down into the Earth’s atmosphere creating a fiery explosion around 1,500 years ago...

Mercury reflects very little light but its surface is low in iron, which rules out the presence of iron nanoparticles, the most likely "darkening agent". First, researchers modelled how much carbon-rich material could have been dropped on Mercury by passing comets. Then they fired projectiles at a sugar-coated basalt rock to confirm the darkening effect of carbon. Their results, published in the journal Nature Geoscience, support the idea that Mercury was "painted black" by cometary dust over billions of years. The effect of being intermittently blasted with tiny, carbon-rich "micrometeorites", the team says, is more than enough to account for...