The theory of evolution by natural selection forced a paradigm shift in our understanding of biology by providing a framework by which living organisms change over time. Through this lens, we have been able to create huge family trees of plants and animals, tracing them back billions of years to the earliest life forms on our planet. However, once we get to the beginning, things get more complicated.
One of the perennial questions in science is how life on our planet came about in the first place. Some support the notion of abiogenesis, in which life arose from non-living prebiotic chemicals. Others are kicking the can a little further down the road, suggesting that life originated elsewhere in the universe and was brought here when Earth was young. A growing body of scientific evidence suggests that at least the essential building blocks of life can form in space.
The near-vacuum of molecular clouds—huge accumulations of gas and dust that eventually collapse into stellar systems—are proving to be pretty good gardens in which to grow some of the basic ingredients of life. New research by Serge Krasnokutski of the Laboratory Astrophysics Group at the Max Planck Institute for Astronomy and colleagues adds peptides to the list of organic molecules that can form in space. Your insights were published in the journal natural astronomy.
“We have previously discovered the formation of biomolecules in a variety of ways, most commonly through energetic processes. in the the Miller-Urey experimentsthey created electrical sparks in a glass jar that lead to the formation of biomolecules,” Krasnokutski told SYFY WIRE. “These energetic processes randomly destroy chemical bonds. It’s not an efficient way to get biological molecules.”
Scientists wanted to find a way to build biomolecules like peptides in an environment similar to the conditions found in molecular clouds in space, but there appeared to be a significant obstacle. On Earth, the process by which peptides are formed requires first the introduction of water and then the removal of water in subsequent steps.
Krasnokutski wondered if there was a way to skip the water steps and get to peptides through a different chemical route. To find out, they built an analogue of space in the lab to see what chemical reactions might occur.
“We have a high-vacuum chamber that allows us to get into a vacuum state similar to that found in the dense regions of the interstellar medium. Then we have a substrate in the chamber that is cooled to 10 Kelvin,” Krasnokutski said.
This substrate replaces the dust particles present in space. The team then deposited carbon monoxide, ammonia and single carbon atoms – chemicals common in target regions of space – on the substrate where the gases freeze.
“When carbon atoms arrive at the ice surface, we see reactions taking place. We found that they are extremely reactive with almost all of the molecules we studied, even at this very low temperature,” Krasnokutski said.
Under these conditions, these reactions form aminoketenes, the precursors to peptides. Then these aminoketenes meet and react to form peptides without having to go through the complex water reactions previously thought to be necessary.
So far they have been able to form glycine peptides through this process, but Krasnokutski is hopeful that other peptides and even proteins could be formed through similar processes. If confirmed, it could fill in some of the gaps in our picture of how life formed on Earth.
“The formation of peptides in space would definitely affect the origin of life,” Krasnokutski said. “If these peptides, or even proteins, can be delivered to the surface of planets, these molecules could trigger the formation of complex organic systems. At this point we have found this formation, everything else is speculation.”
We may not be aliens on our own planet, but there’s a chance that at least some of our most basic parts are extraterrestrial in origin. We don’t know about you, but we think that’s pretty cool.