Trying to piece together the appearance of life on Earth is a little like looking through a kaleidoscope. There are competing theories for where Earth’s water came from, and there’s incomplete evidence for how the Moon formed and what role it played in life’s emergence. There are a thousand other questions, each with competing answers. Sometimes, contradictory research is published within days of each other.
But that’s nature, and that’s part of the thrill of science. There’s rigorous determination behind all the evidence and inquiry, and the kaleidoscope calms down over time. Order emerges, and the picture becomes clearer.
Asteroids are one of the moving pieces in the kaleidoscope. An asteroid impact caused the most dramatic extinction in Earth’s history. But they may have delivered some of Earth’s water and the basic chemistry for life. Their impacts may have created niches for life, too. Asteroids are dangerous but also beneficial. Like many things in nature, it’s all about the amount.
A new research paper looks at other solar systems to see if they have asteroid belts. If they do, the asteroids in those belts could contribute to habitability on planets in those systems. The paper is “Asteroids and life: How special is the solar system?” and it’s available on the pre-print site arxiv.org. The lead author is Rebecca Martin, an associate professor in the Physics and Astronomy Department at the University of Nevada, Las Vegas.
It’s enticing to look at our neighbours in the Solar System and come to simple conclusions. The asteroid-blasted surfaces of Mercury, the Moon, and Mars look like they’ve had the life battered right out of them (if any of them ever hosted any life.) But simple conclusions often come back to haunt us, and that’s true of asteroids.
Asteroid impacts may have given life on Earth a helping hand. Their impact craters were new types of habitats, and habitat variety can be good for life. Asteroid impacts can create systems of hydrothermal vents underground that can aid life. The Chicxulub impact that ended the dinosaurs created a vast system of hydrothermal vents that lasted over one million years and chemically and mineralogically modified a giant chunk of the Earth’s crust. Chemical and mineralogical variety can be good for life.
This figure is a model of the temperature at the Chicxulub impact site based on borehole samples. The impact created a system of hydrothermal vents that lasted over one million years. The impact was apocalyptic for dinosaurs, but other similar impacts further back in Earth’s history may have aided life’s emergence. Image Credit: Abramov and Kring 2007.
Asteroid impacts created clays that may have played a critical role in developing simple organic molecules like formaldehyde and more complex molecules like RNA. Asteroid impacts may have been essential for the transition from chemistry to biology. Their impacts could’ve changed Earth’s atmosphere into something more conducive to life when their iron cores reacted with ocean water to release hydrogen. The resulting atmosphere may have paved the way for the emergence of organic molecules.
Nature keeps rotating the kaleidoscope, and scientists keep peering into it.
“Given the mounting evidence for the potential role of asteroids in the emergence of life on Earth, it is not unreasonable to assume that asteroid impacts on a terrestrial planet (in the habitable zone of its host star) are a necessary condition for the emergence of life and to study the consequences of this assumption,” the authors explain.
In our Solar System, asteroids are concentrated in the asteroid belt. If asteroids help enable life’s emergence, then asteroid belts might be necessary for life to emerge on exoplanets in other solar systems. Or, at the very least, helpful.
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