Experts argue that targeting water-rich planets in the search for extraterrestrial life wastes valuable resources. Instead, astronomers should prioritize worlds rich in phosphorus and nitrogen, essential elements for life.
Essential Elements for Life
Phosphorus forms the backbone of DNA and RNA, storing and transmitting genetic information. Nitrogen builds proteins, the fundamental components of cells. Without these in a planet’s rocky mantle, life cannot emerge, regardless of abundant water.
Dr. Craig Walton of ETH Zurich explains: “You could feasibly have a planet that looks great with oceans and even dry land, but there is no life and never will be because the other elements you need are simply all but absent.”
The Chemical Goldilocks Zone
Planets form from molten rock, where heavy elements like iron sink to the core and lighter ones rise to the mantle and crust. Oxygen levels during formation critically influence phosphorus and nitrogen availability.
Excess oxygen traps phosphorus in the mantle and expels nitrogen to space. Insufficient oxygen pulls phosphorus into the core. Numerical models reveal a narrow ‘chemical Goldilocks zone’ where both elements concentrate in the mantle, enabling life.
Earth resides squarely in this zone by chance, but habitable planets may number just 1 to 10 percent of prior estimates.
Implications for Exploration
Current focus on oxygen-rich atmospheres as habitability signs may mislead. Dr. Walton warns: “It would be very disappointing to travel all the way to such a planet to colonise it and find there is no phosphorus for growing food.”
Researchers advise checking planetary formation conditions beforehand, akin to verifying food safety before consumption.
Mars and Beyond
Mars falls outside this zone, boasting ample phosphorus but scarce surface nitrogen, plus toxic salts. Dr. Walton notes: “Mars is fairly similar to Earth… This means growing food there might be relatively easy,” yet major alterations remain necessary for habitability.
Future searches should analyze host star compositions, as planets inherit similar chemistry. Systems mirroring our Sun offer prime targets for life.
