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When a massive asteroid collided with Earth 66 million years ago, the resulting dust clouds blocked the sun for approximately 15 years. Recent research suggests that this dust may have been the main factor behind the mass extinction event that led to the demise of non-avian dinosaurs and numerous other species.
The impact of the Chicxulub asteroid released sulfur-based gases and vast amounts of silicate dust into the atmosphere. It also triggered global wildfires that emitted soot and carbon dioxide.
The aftermath of this event resulted in an “impact winter,” which contributed to the extinction of 75% of the planet’s species.
Previous studies focused on the role of sulfuric gas emissions or soot injections from wildfires, without considering the potential impact of silicate dust.
To explore this further, Cem Berk Senel and his team analyzed fine-grained material deposited at a site in North Dakota during the Chicxulub impact. The researchers found that the grains ranged from 0.8 to 80 micrometers in diameter, with an average size of 2.88 micrometers.
Using a climate model, the team discovered that sulfur gases initially played a primary role in global cooling by blocking sunlight. However, these gases only remained in the atmosphere for about eight years. In contrast, silicate dust persisted for 15 years after the impact, indicating its significant contribution to sustaining the global winter. The researchers observed that the dust alone caused a 15°C drop in Earth’s surface temperature, and its effect gradually diminished after the initial years.
Notably, the silicate dust was more effective than sulfur gases at blocking the wavelengths of light necessary for photosynthesis in plants and phytoplankton.
According to Senel, the silicate dust resulted in a prolonged shutdown of photosynthesis after the impact, leading to a lack of food for many species and subsequent extinctions on land and in the oceans.
The researchers plan to further investigate the long-term climatic effects of the asteroid impact and continue unraveling the mysteries around one of the most significant mass extinction events in history.
