The mystery of life’s origins on Earth persists, but scientists are making strides in unraveling the processes and components involved. The prevailing theory suggests that life emerged from a primordial mixture of organic chemicals and biomolecules on early Earth, eventually evolving into living organisms.
It has long been hypothesized that some of these crucial ingredients could have arrived from space. A recent study, published in Science Advances, reveals that peptides, a special class of molecules, may form more readily under space conditions compared to those found on Earth. This suggests that these molecules could have been transported to early Earth via meteorites or comets, potentially paving the way for life to develop elsewhere in the universe.
Life’s essential functions are sustained by proteins, large and complex carbon-based molecules found within cells. The blueprint for producing the vast array of proteins required for life is stored in DNA, another intricate organic molecule.
However, these complex molecules are synthesized from simpler building blocks known as amino acids—the fundamental components of life.
To comprehend life’s origins, researchers must understand how and where these building blocks originate and under what conditions they spontaneously organize into more intricate structures. Finally, scientists aim to decipher the crucial step that transforms these structures into self-replicating systems—living organisms.
The recent study sheds light on the potential formation and assembly of some of these building blocks, shedding insight on their journey to Earth.
DNA, consisting of two long strands forming a double helix, is composed of smaller units called nucleotides. Each nucleotide contains three elements: a sugar molecule (deoxyribose in DNA), a phosphate group, and a nitrogenous base. These bases—adenine (A), thymine (T), cytosine (C), and guanine (G)—pair up specifically to form the rungs of the DNA ladder.
Peptides, on the other hand, are chains of amino acids. They play crucial roles in catalyzing biochemical reactions essential for life and could have been involved in forming early versions of cell membranes.
Despite their potential significance, peptides were not thought to form spontaneously under Earth’s conditions. However, recent research has shown that the cold environment of space is more conducive to peptide formation.
In the low-density environment of interstellar clouds, carbon atoms can adhere to dust grains, reacting with carbon monoxide and ammonia to form amino acid-like molecules. As these clouds condense into denser structures like asteroids and comets, peptides can assemble, aided by the presence of water molecules.
Laboratory experiments emulating interstellar reactions demonstrate that peptide formation, although slightly hindered, is not obstructed. Furthermore, as asteroids and comets heat up and form liquids, peptide formation is enhanced, leading to the creation of more complex organic molecules. These processes likely occurred during the formation of our solar system.
Given that many essential building blocks of life can form in space, and considering the efficiency of peptide formation in these conditions, it’s plausible that extraterrestrial impacts delivered loads of these molecules to early Earth, potentially facilitating the emergence of life.
In essence, the availability of life’s building blocks throughout the universe suggests that the conditions necessary for their self-assembly into living organisms remain a key question. Answering this question will provide insights into the potential prevalence of life beyond Earth.
