Craig Walton, astrobiologist, our planet has life thanks to being in its chemical Goldilocks zone at birth: “Earth is precisely within this range”

Earth finds itself among the fortunate planets in the universe. Among its many blessings, it has plentiful water which is considered essential to the formation of life.

Furthermore, our planet is located within the ‘Goldilocks’ habitable zone from the Sun. That helps keep things for the most part on the surface of Earth not too hot and not too cold, so that the water doesn’t boil off but can still be in liquid form.

But according to new research by a group of researchers at ETH Zurich it also happened to have another thing going for it. At its birth, Earth found itself within a “chemical Goldilocks zone” as well that made it possible for life to develop.

Earth’s stroke of luck that made life possible

Water is just one of the necessities for the formation of life. Organic molecules must also be present, along with two essential elements, phosphorus and nitrogen. If these aren’t present in sufficient amounts in a planet’s surface at birth, life won’t have a chance of getting started.

Phosphorus is a key ingredient in the formation of DNA and RNA, and the energy balance of cells. Nitrogen, on the other hand, is vital component of proteins, without which cells cannot form or function.

In order that phosphorus doesn’t sink into the core or nitrogen jettison out into space as the planet is taking shape, there has to be just the right chemical balance of another key element in the developing core of the new planet, according to the findings of the study led by Craig Walton, postdoc at the Centre for Origin and Prevalence of Life at ETH Zurich, and ETH professor Maria Schönbächler.

“During the formation of a planet’s core, there needs to be exactly the right amount of oxygen present so that phosphorus and nitrogen can remain on the surface of the planet,” explained Walton in a statement.

When planet forms, as the Earth did some 4.6 billion years ago, the slurry of material is initially molten. This allows heavier elements to sink toward the center while lighter elements rise to the surface.

Without enough oxygen, phosphorus will fuse to heavier elements like iron and will be pulled with it to the core. Too much oxygen creates conditions that allow nitrogen to be lost to space, as happened on Mars in the researchers’ findings. A deficiency of either of these two key ingredients of life means that there isn’t the chemistry for it form.

“Our models clearly show that the Earth is precisely within this range. If we had had just a little more or a little less oxygen during core formation, there would not have been enough phosphorus or nitrogen for the development of life,” he added.

Study’s findings can help in the search for life on exoplanets

Walton and Schönbächler hope that their research will help change the focus of how we search for life on other planets in the universe. While a planet may have water, that doesn’t necessarily mean that it started with the right chemical balance to make it suitable for life.

They want astronomers to look beyond the habitable zone around a star and take into account whether a planet was within the chemical Goldilocks zone as well. They say that those hunting for signs of life in the universe should focus their energy on looking at those planets that are orbiting stars similar to our Sun.

“This makes searching for life on other planets a lot more specific,” Walton said.

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