A multidisciplinary team of researchers involving astrophysicists, astrochemists and biochemists, has reported the detection of the prebiotic molecule ethanolamine in space, which could have been incorporated into the early Earth. This species forms the simplest head of phospholipids that make up the membranes of all present-day cells.

Discovery of ethanolamine, the simplest head of phospholipids (building blocks of cell membranes) towards the molecular cloud G+0.693-0.027 located in the center of our Galaxy. Credits: Víctor M. Rivilla & Carlos Briones (Centro de Astrobiología, CSIC-INTA) / NASA Spitzer Space Telescope, IRAC4 camera (8 microns).

The appearance of cell membranes represents a crucial step in the origin and early evolution of life on Earth, as they compartmentalize the cell and thus hold together its genetic material and metabolic machinery. However, the origin and evolution of the cell membrane is unclear. A team led by Víctor M. Rivilla, researcher at the Center of Astrobiology in Madrid (CSIC-INTA, associated to the NASA Astrobiology Program), has detected the presence of ethanolamine (NH₂CH₂CH₂OH), one of the key components of the head of phospholipids that build-up the cellular membranes. The molecule was detected in a molecular cloud near the galactic center using the IRAM 30-meter and Yebes 40-meter radiotelescopes in Spain. “These results suggest that ethanolamine forms efficiently in interstellar space in molecular clouds where new stars and planetary systems form”, says Víctor M. Rivilla.

Ethanolamine is the simplest molecule that, together with a phosphate group, forms the head of phospholipids. The measured abundance of this molecule in the interstellar medium relative to water shows that it likely formed in space and could be later incorporated into meteorites. “We know that a broad repertoire of prebiotic molecules could have been delivered to the early Earth through the bombardment of comets and meteorites”, says Izaskun Jiménez-Serra, one of the co-authors. “We estimate that around 1 million of billions (10¹⁵) of litres of ethanolamine might have been delivered to the early Earth through meteoritic impacts. This is equal to the total volume of Lake Victoria, Africa's largest lake by area”, adds Jiménez-Serra.

Experiments simulating the chemical conditions on early Earth confirm that ethanolamine could have produced phospholipids at the dawn of our planet. Carlos Briones, a biochemist who co-authored the work, comments: “The availability of ethanolamine on the early Earth, together with fatty acids or alcohols, may have contributed to the assembly and early evolution of primitive cell membranes. This has important implications not only for the study of the origin of life on Earth, but also on other habitable planets and satellites anywhere in the Universe”.

The interstellar hunt of new prebiotic molecules in the interstellar medium does not stop here, and will continue in the following years. “Thanks to the improved sensitivity of the current and next generation of radiotelescopes, we will be able to detect interstellar molecules with increasing complexity that are direct precursors of the three basic components of life: lipids which form the membranes, RNA and DNA nucleotides which contain the genetic information, and also proteins that are responsible for the metabolic activity, says Víctor M. Rivilla. “Are these prebiotic seeds distributed across the whole Galaxy, and even in other galaxies? We will know relatively soon”, concludes Rivilla.

More information:

Article published by the Proceedings of the National Academy of Sciences of the United States of America (PNAS) #21-01314: “Discovery in space of ethanolamine, the simplest phospholipid head group” by Víctor M. Rivilla et al.

Contact:

Víctor M. Rivilla
Centro de Astrobiología de Madrid (INTA-CSIC)