When it comes to life and its history on Earth, meteorite impacts have been one of the ever-present threats to total extinction. It’s even possible that life may have had multiple beginnings — with early iterations being utterly destroyed by the impact of a massive body early in Earth’s history.
We know, though, that life has managed to expand and diversify into almost every available ecological niche on the planet and that all life on Earth can be traced back to a last universal common ancestor that existed some 3.6 billion years to 4.2 billion years ago. Since then, impacts on Earth’s surface have regularly disrupted the living order, yet life remains.
Meteorite impacts, when viewed through their ability to radically alter Earth’s environment, have been considered a force for destruction. However, with a more nuanced perspective on the history of life on Earth, along with a greater understanding of the role that meteorite impacts have had in shaping the world we live in, scientists are reconsidering these events as detrimental to a planet’s ability to support life.
How Meteorites Shaped Earth’s Evolution
Alexandra Pontefract, a microbiologist who specializes in how impacts influence planetary habitability from Johns Hopkins’ Applied Physics Laboratory, thinks that the sentiment that impacts are detrimental to life can be traced back to our understanding that the mass extinction of the dinosaurs was due to a large impact at the end of the Cretaceous.
“At this time, the existence of a global layer of iridium, marking the end of geologic preservation of dinosaurs, was discovered, resulting in a groundbreaking hypothesis that a large meteorite impact caused a global extinction level event,” Pontefract says.
“The idea that we could be wiped out by this type of global catastrophe is also something that captures our imaginations, and this filtered into popular culture in the 1990s, with Deep Impact and Armageddon, fomenting the idea that a giant fiery ball heading towards us is generally not a good thing,” she continues.
Asteroid Dust and Its Role in Supporting Life
However, through Pontefract’s work and others, researchers are realizing that meteorite impacts on planetary (and moon) surfaces can also positively shape habitable conditions.
Take, for example, the work done by Kurosawa, who showed that carbon-rich asteroids can react with atmospheric nitrogen to produce hydrogen cyanide — which is thought to be one of the most important chemical precursors to the origin of life. Smaller asteroids, as well as the constant infall of interplanetary dust, are also a source of biologically relevant organics to planetary surfaces, such as sugars, amino acids, and carbohydrates.
“It is important to note that this infall would have been higher early on in the evolution of the solar system due to the higher concentrations of asteroids and co
