Cosmic origins of phosphorus, a building block for life, traced by scientists

Jan. 15 (UPI) -- Using the combined powers of ALMA, a powerful observatory, and Rosetta, the European Space Agency's comet-studying probe, scientists have for the first time observed the precise cosmic origins of phosphorus, an element essential to life.

The new research, published Wednesday in the journal Monthly Notices of the Royal Astronomical Society, also showed how phosphorus is carried by comets.

Scientists were able to locate phosphorus in the star-forming region AFGL 5142. The astronomers' attraction to AFGL 5142 was two-fold.

"AFGL 5142 is relatively close to us and therefore you can get the necessary spatial resolution," study author Kathrin Altwegg, an astrophysicist at the University of Bern in Switzerland, told UPI. "Scientists also believe by now that our sun emerged from something similar: a massive cloud where large and small stars are formed simultaneously."

Researchers have previously found phosphorus in distant regions of space, but were unable to pinpoint the precise location of the element within star-forming regions. The power of the Atacama Large Millimeter/submillimeter Array, located in the Chilean desert, allowed scientists to determine the exact location of cosmic phosphorus within AFGL 5142.

"Thanks to the unique sensitivity and spatial resolution of this instrument, we have been able to map for the first time the emission of molecules with phosphorus, and connect it to local physical/chemical properties," lead study author Victor Rivilla, researcher at the Arcetri Astrophysical Observatory of INAF, Italy's National Institute for Astrophysics, told UPI in an email.

The ALMA data showed the phosphorus is located on the walls of a cavity shaped by the molecular outflow produced by a newly formed star.

"This has allowed us to understand that the molecules are formed during the formation of new stars thanks to the combination of two physical processes: shocks created by protostellar outflows and photochemistry triggered by ultraviolet radiation from the protostar," Rivilla said.

To determine how phosphorus might have been carried to Earth, scientists analyzed data collected by ROSINA, the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis.

For two years, ESA's Rosetta probe circled the comet 67P/Churyumov-Gerasimenko, all the while using its mass spectrometer to study its chemical composition. Scientists previously found the signatures of phosphorus in the ROSINA data, but weren't sure what molecules the phosphorus atoms were linked with. A reexamination of the ROSINA data revealed the presence of phosphorus monoxide, PO, on the comet.

In the earliest days of the solar system, most of the phosphorous remained trapped inside icy mineral grains, and thus, not available for chemistry. The discovery of phosphorus monoxide offers clues as to how phosphorus became available to chemistry and made it possible for life to begin on primordial Earth.

"These icy grains finally formed comets," Altwegg said. "Closer to the sun, at the position where the Earth formed, the ice sublimated and then species like PO underwent chemistry. That's why scientists asked for a long time how it was possible to start life on the early Earth as you need phosphorous in a chemical active form, not in minerals. PO might give the explanation."

While a combination of findings, made possible by ALMA and ROSINA, supports the theory that comets played a vital role in delivering the building blocks of life to planet Earth, scientists suggest this is only part of the story of life's cosmic beginnings.

"We have to strengthen the link from clouds to protostars, planets, comets and then Earth by looking at other molecules, isotopes, studying more star forming regions with different characteristics and of course, more comets," Altwegg said.