In the vast reaches of the cosmos, Earth may have been blessed with extraordinary chemical fortune, determining its habitability. According to a recent study by ETH Zurich, during the early formation of our planet, oxygen had to be in an extremely narrow zone, termed the ‘Goldilocks zone’, for two life-essential elements, phosphorus and nitrogen, to remain available in adequate quantities.
These elements are crucial: phosphorus is fundamental in the construction of DNA and RNA, while nitrogen is an essential part of proteins. Without them, life could not emerge. Craig Walton, a researcher at the Center for the Origin and Prevalence of Life at ETH Zurich, along with Professor Maria Schönbächler, led the research highlighting the importance of these elements being present in the correct amounts during the formation of a planet’s core.
During Earth’s core formation, around 4.6 billion years ago, precise oxygen levels allowed phosphorus and nitrogen to remain near the surface, where they could be utilized by life. Otherwise, phosphorus would have bonded with heavy metals and been lost to the core, while nitrogen might have escaped into the atmosphere. This discovery could redefine the search for life beyond Earth, showing that the presence of water is not sufficient.
The model developed by Walton and his co-authors reveals that both phosphorus and nitrogen remain in the mantle in sufficient quantities only within a very narrow range of moderate oxygen conditions. The results indicate that Earth is precisely within this zone. Other planets, like Mars, formed outside this zone, resulting in less favorable conditions for life.
These findings could alter how scientists assess the habitability of other planets. Until now, the emphasis was on the presence of water. Walton and Schönbächler argue that a planet may have water but still be chemically inhospitable from the start if oxygen levels during core formation are inadequate.
Moreover, the chemical composition of a planet’s stellar system can influence these conditions. As planets primarily form from the same material as their stars, solar systems with chemistry vastly different from ours may be poor candidates in the search for life. Walton suggests we should focus on solar systems with stars resembling our Sun.
This research, detailed in the publication ScienceDaily, could revolutionize how we approach the search for life beyond Earth, by highlighting the importance of specific chemical conditions during planetary formation.
Original published at O Cafezinho.