Ingredients for Earth: A dash of magnesium, a sprinkle of silicon, some carbon and of course oxygen et voilà, you have the basic recipe for a habitable planet.
Of course, that doesn't mean that life will easily spring up in environments possessing these elements, but they are some of the key chemical ingredients we know it needs in order to form. Scientists, though, had thought the chance of crucial minerals formed from these building blocks coming together in the same ratios as Earth, allowing life to form, was relatively rare.
Not any more. New research has suggested that rocky planets are three times more likely than previously thought to have the same type of minerals as our own, to the extent that Earth-like planets have the potential to form in every single planetary system. This is based on a sophisticated model made of the chemical evolution of the Milky Way by the University of Hull, presented at the National Astronomy Meeting in Llandudno, Wales, yesterday.
Minerals made from carbon, oxygen, magnesium and silicon can turn the rocky landscapes of planets from barren, inhospitable worlds to something more akin to Earth. But just a very small change in the recipe can dramatically alter the temperature and even the plate tectonics on a planet, dictating whether it is habitable or not. Only a third of rocky planets were thought to have the correct ratio.
"Too much magnesium or too little and your planet ends up having the wrong balance between minerals to form the type of rocks that make up the Earth’s crust," Professor Brad Gibson, who led the research, said in a statement. “Too much carbon and your rocky planet might turn out to be more like the graphite in your pencil than the surface of a planet like the Earth."
But using the model, the astronomers at the E.A. Milne Centre for Astrophysics calculated the chances of life’s chemical building blocks existing in the right amounts, and found they could be present in every planetary system, not just a third. "At first, I thought we’d got the model wrong!" Gibson explained.
"Everything was in the right place; the rates of stars forming and stars dying, individual elements and isotopes all matched observations of what the Milky Way is really like. But when we looked at planetary formation, every solar system we looked at had the same elemental building blocks as Earth, and not just one in three."
The mineralogy of rocks on Earth, such as these seen on the Kamchatka Peninsula, provided some of the chemical building blocks for life. Credit: Europlanet/A. Samper
Based on their model, they found that these elemental building blocks are found in every exoplanet system no matter where it is in the galaxy. Of course, there are many other requirements for life to form, such as a planet being in its star’s habitable zone where temperatures are not too hot or cold for liquid water to exist.
Importantly, though, this discovery at least increases the chance of Earth-like planets forming by a factor of three, and tentatively suggests that some of the chemical ingredients for life are not that rare.