Is the threat of a civilization-ending asteroid strike higher than we thought?
In short: Earth is constantly bombarded by space debris, from daily dust showers to annual fireballs. While we often view giant impacts as once-in-an-epoch catastrophes, new satellite data suggests our historical records might be undercounting the true frequency of these devastating cosmic collisions.
The frequency of asteroid impacts depends entirely on the size of the object. Every day, Earth is struck by over 100 tons of dust and sand-sized particles. On a larger scale, an automobile-sized asteroid enters the atmosphere and creates a fireball roughly once a year, while a football-field-sized meteoroid causes significant local damage about every 2,000 years. However, objects large enough to threaten human civilization are estimated to strike only once every few million years.
The difficulty in measuring these rates stems from the fact that many space rocks vaporize in the atmosphere, and those that do land are often eroded by wind and water. To counter this, scientists use high-resolution satellite data to examine impact craters. A recent NASA-funded study led by James Garvin suggests that large asteroids may hit Earth more frequently than previously cataloged. By identifying large rings in satellite data, the team argues that certain craters are tens of miles wider than once thought, implying far more powerful impacts occurred in the past million years.
This finding is currently a point of scientific contention. While the study suggests a higher risk, other researchers, such as Anna Łosiak and Gordon Osinski, argue that the 'rings' identified in the data may not be structural crater features but rather subtle artifacts. While the consensus remains that no large asteroids pose an immediate threat to Earth for the foreseeable future, the debate highlights the complexity of planetary defense: we are still refining our understanding of how often 'serious crap' happens from above.
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Sources
- Summary by Intellect · source: How Often do Asteroids Hit the Earth?: Crash Course Geology #20
- Also: Asteroid Fast Facts - NASA
- Also: Big asteroids hit Earth more frequently than thought: study | Space
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