The emergence of life on Earth is a mystery. What were the conditions that made it possible for life to happen here? We do not know. We also don’t know if those conditions are an absolute requirement or if there are different ways for life to come out of the inorganic universe. A group of researchers now think that there are hundreds of paths that life might have taken.
It all boils down to repeating chemical reactions, specifically self-sustaining repetition. Also known as autocatalysis, this requirement pushes all the possible combinations of chemical elements, the ingredients the universe has available, only towards specific reactions. And this new work suggests that there are more ways to mix them together.
“It was thought that these sorts of reactions are very rare. We are showing that it's actually far from rare. You just need to look in the right place,” Betül Kaçar, a NASA-supported astrobiologist and University of Wisconsin–Madison professor of bacteriology, said in a statement.
“We will never definitively know what exactly happened on this planet to generate life. We don't have a time machine. But, in a test tube, we can create multiple planetary conditions to understand how the dynamics to sustain life can evolve in the first place.”
Kaçar and her team, led by postdoctoral researcher Zhen Peng, found 270 combinations of molecules with autocatalytic properties using elements across the periodic table. In particular, they were looking for comproportionation reactions. These produce multiple copies of the same molecules, and the more molecules that are produced, the faster the reaction gets.
“If those conditions are right, you can start with relatively few of those outputs. Every time you take a turn of the cycle you spit out at least one extra output which speeds up the reaction and makes it happen even faster,” co-author Zach Adam explained.
The authors have likened this approach to a recipe book. A recipe book that is more complex than expected. Not every one of these reactions might lead to life but the fact that there are many could imply that life might find many ways to emerge.
“Carl Sagan said if you want to bake a pie from scratch, first you must create the universe,” Kaçar said. “I think if we want to understand the universe, first we must bake a few pies.”
The research is published in the Journal of the American Chemical Society.