Scientists Reveal Hidden Danger of Cosmic Airbursts
Scientists from UC Santa Barbara have uncovered new evidence showing that cosmic airbursts—explosions of comets or asteroids in the atmosphere—may be more common and destructive than traditional crater-forming impacts.
These “touchdown” airbursts release intense heat and pressure but often leave little to no visible crater, making them harder to study.
In a series of four recent studies, Professor James Kennett and his colleagues presented findings from sites ranging from the deep ocean floor near Greenland to ancient desert settlements. They identified impact markers such as rare cometary minerals, molten glass, tiny spherules formed by extreme heat, and shocked quartz—a type of quartz fractured by high pressure.
One study revealed, for the first time, evidence of the Younger Dryas Impact event in marine sediments from Baffin Bay off Greenland’s coast. This event, about 12,800 years ago, involved a fragmented comet exploding above Earth and is linked to sudden global cooling, mass extinctions, and cultural changes in human populations. The researchers found layers of carbon-rich sediment containing high levels of platinum and iridium along with impact-related materials deep below the ocean surface.
Another study investigated a shallow lake near Perkins, Louisiana, which may be the first known crater associated with the Younger Dryas Boundary. Sediment samples from the site contained impact spherules, meltglass, and shocked quartz dating to the event, although further research is needed to confirm the crater’s origin.
The team also revisited the 1908 Tunguska airburst in Siberia, the only recorded touchdown event in history. Their analysis found shocked quartz grains with distinctive fractures, impact spherules, melted metals, and carbon in the soil. These findings provide the first comprehensive evidence of impact materials at the site, complementing eyewitness accounts and observations of flattened trees.
In addition, the researchers expanded evidence for a Bronze Age airburst over Tall el-Hammam in the southern Jordan Valley. They identified a variety of shocked quartz fracture patterns similar to those at Tunguska, indicating complex high-pressure impacts. These findings support the idea that ancient airbursts caused widespread destruction.
The studies suggest that touchdown airbursts may happen far more frequently than previously believed. Unlike classic crater-forming impacts, these events can cause widespread damage through intense heat and shockwaves without leaving large craters. According to Professor Kennett, they deserve closer scientific attention due to their potential impact on Earth’s climate, ecosystems, and human history.
