"Scientists hunting for life beyond Earth have long thought that water is one of the key indicators. But a group of experts now says that looking for life on water-rich planets could be a waste of time. Instead, they claim we should be turning our telescopes to worlds that are filled with phosphorus and nitrogen. Life as we know it simply cannot form without these two elements - even if there's abundant water."
"Phosphorus is required to make DNA and RNA, which store and transmit genetic information in all lifeforms. Nitrogen, meanwhile, is an essential component of proteins, which are the basic building blocks of cells. This means that life can only form on worlds within the 'chemical Goldilocks zone', where there is just the right amount of nitrogen and phosphorus in the rocky mantle."
"Lead author Dr Craig Walton, of ETH Zurich, told the Daily Mail: '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.' While no life as we understand it can survive without liquid water and oxygen, looking for planets that have these ingredients might be misleading."
"This is because a planet's 'oxygen balance' at the moment of its formation determines how much phosphorus and nitrogen remain available for life. When planets cool out of molten rock, a sorting process happens in which the heavy elements like iron sink towards the core, while lighter ones float to the surface to form the mantle and crust. If there is too much oxygen present, phosphorus gets locked in the mantle while nitrogen is forced out into the atmosphere and eventually lost into space."
Planets with abundant surface water can still be incapable of supporting life if they lack sufficient phosphorus and nitrogen in their rocky mantles. Phosphorus is essential for forming DNA and RNA; nitrogen is essential for proteins. A 'chemical Goldilocks zone' of mantle composition is required for biogenesis. The overall planetary oxygen balance during formation controls element partitioning: cooling from molten rock causes heavy elements to sink to the core and lighter elements to float to the mantle and crust. Excess oxygen locks phosphorus into oxidized forms and drives nitrogen into the atmosphere to be lost; insufficient oxygen binds phosphorus into the core.
Read at Mail Online
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