Found in DNA and cell membranes, phosphorous is a crucial building block for life. New research suggests that this important element may have been seeded on Earth by comets.

The question of how phosphorous — an essential building block of life — first became available on Earth 4-billion years ago at the dawn of life has puzzled scientists for decades. Now, astronomers believe they have found the answer, their research suggests that the element — born in star-forming regions of space — was likely deposited on Earth by comets. The researchers also found that the molecule phosphorous monoxide could have played a vital role in the formation of life.

The background of this infographic shows a part of the night sky in the constellation of Auriga, where the star-forming region AFGL 5142 is located. The ALMA image of this object is on the top left of the infographic, and one of the locations where the team found phosphorus-bearing molecules is indicated by a circle. The most common phosphorus-bearing molecule in AFGL 5142 is phosphorus monoxide, represented in orange and red in the diagram on the bottom left. Another molecule found was phosphorus mononitride, represented in orange and blue. Using data from the ROSINA instrument onboard ESA’s Rosetta, astronomers also found phosphorus monoxide on comet 67P/Churyumov–Gerasimenko, shown on the bottom right. © ALMA (ESO/NAOJ/NRAO), Rivilla et al.; ESO/L. Calçada; ESA/Rosetta/NAVCAM; Mario Weigand, www.SkyTrip.de

“Life appeared on Earth about 4 billion years ago, but we still do not know the processes that made it possible,” says Víctor Rivilla from the National Institute of Astrophysics INAF in Florence, and lead author of a new study published in the journal Monthly Notices of the Royal Astronomical Society.

In order to conduct their study, the team utilised the European Southern Observatory’s (ESO) Atacama Large Millimeter/submillimeter Array (ALMA) located on the Chajnantor plateau in the Chilean Andes. With the aid of the 66 high-precision antennas and the sophisticated interferometer that comprise ALMA, the team conducted an intense and detailed study of the star-forming region known as AFGL 5142. Their observations revealed that molecules containing phosphorous — such as phosphorous monoxide — form as massive star ignite.

The stunning Milky Way above the antennas at the ALMA Observatory. © Y. Beletsky (LCO)/ESO

“Flows of gas from young massive stars open up cavities in interstellar clouds. Molecules with phosphorus form along the cavity walls through photochemistry,” Maria Drozdovskaya, from the Center for Space and Habitability (CSH) and the University of Bern, explains. In star-forming regions, the study shows, phosphorous monoxide can ‘freeze out’ — becoming trapped in ice surrounding interstellar dust grains. As the budding solar system develops and in the infancy of the stars within the system, these icy grains of dust clump together, thus forming pebbles, planetesimals, and ultimately, comets.