If you were to choose one element that represents life, the answer would likely to be carbon. With the readiness to react with other basic elements and capability to form hundreds of thousands of organic compounds, it is no doubt the most essential chemical component that forms life.
However, many other elements such as phosphorus and iron are also essential for sustaining life. Besides being the main element of the core of our rocky planet, iron also plays an irreplaceable role in oxygen-breathing life-forms due to its ability to bind oxygen. By linking deoxyriboses in DNA, phosphorus is responsible for the chain-like structure of genetic materials for almost life-forms on Earth. What's more, phosphorylation turns ADP into ATP, enabling the generation of energy molecules in cellular respiration.
Scientists have already found carbon molecules, large and small littered in all over the space, even in the outer planets of our solar system such as Uranus and Neptune. Their iconic blue color is caused by the presence of methane in the atmosphere. Methane can undergo photolysis, producing trace amounts of other hydrocarbons. These include alkanes, particularly ethane, as well as various unsaturated hydrocarbons.
Related reading: Organic Compounds in the solar system
But what about iron and phosphorus? Are those elements as abundant as carbon in the universe? According to a recent study, a team of Cardiff University astronomers has provided a less optimistic answer: no, at least in the galaxies they have surveyed.
Heavy elements such as phosphorus and iron are created in stars through nuclear fusion and later spilled all over the space through explosion like the supernovae. Using the William Herschel Telescope, the British scientists searched for the infrared light emission signature of phosphorus and iron in two groups of the supernova remnant, one located in the Crab Nebula (6,500 lightyears away from Earth) and the other at the constellation Cassiopeia (11,000 lightyears away). The results suggested that in general there is a lack of elements such as phosphorus and iron.
Between the two observed remnants, the one in the Crab Nebula appeared to much less phosphorus than in Cas A. To confirm this conclusion, however, the team would require extra time on the telescope and survey all parts again in case missing certain phosphorus-rich regions.
During an interview with the Royal Astronomical Society, Jane Greaves, the lead author of the study said: "The route to carrying phosphorus into new-born planets looks rather precarious. We already think that only a few phosphorus-bearing minerals that came to the Earth—probably in meteorites—were reactive enough to get involved in making proto-biomolecules."
"If phosphorus is sourced from supernovae, and then travels across space in meteoritic rocks, I'm wondering if a young planet could find itself lacking in reactive phosphorus because of where it was born? That is, it started off near the wrong kind of supernova? In that case, life might really struggle to get started out of phosphorus-poor chemistry, on another world otherwise similar to our own," she added.
Even though some may conclude that the scarcity of phosphorus in space could be the reason why alien life-forms are so hard to emerge therefore difficult to be detected, it is entirely possible that life can still exist but with biochemical mechanisms that do not rely on phosphorus.
Source: Seeker via Youtube