The earth was formed relatively quickly from the cloud of dust and gas surrounding the Sun, while taking from it water and gases, some of which are now locked in the mantle of the planet. These are the isotopes of the neon, extracted from the pillow lava at the bottom of the ocean. The discovery sheds light not only on the birth story of our home, but also in the future will help to identify the potentially inhabited stellar systems.
We were trying to understand where and how the neon was acquired in the mantle of the Earth, which tells us how quickly and in what conditions the planet was formed.
-Curtis Williams, co-author of a study from the University of California, Davis, USA
Neon, unlike compounds such as water, carbon dioxide and nitrogen, is an inert noble gas, and it is not influenced by chemical and biological processes. Thus, he keeps the memory of where he came from, even after four and a half billion years and can tell about the history of our planet.
Today there are three competing theories about the formation of the Earth and how water and other gases were delivered to a growing planet. The first one says that it grew relatively fast during two to five million years and captured all necessary for life from the surrounding young Sun of the Cloud. The second relies on the process of formation of dust grains, which were exposed to the radiation of our star for some time, and then, having condensed into planetzimals, brought water and gases to the developing Earth. In the third variant, the Earth was formed for a long time, and the reserves replenished thanks to the falling meteorites on it, rich in water, carbon and nitrogen.
From the cosmos to the bottom of the ocean
To find out which of the three ideas is true, the scientists conducted an accurate measurement of the ratio of the isotopes of the neon, which were captured by the mantle of the Earth at the time of its formation.
Neon has three isotopes, neon-20, 21, and 22. All of them are stable and non-radioactive, but neon-21 is formed in the decay of uranium. Thus, the number of neon-20 and 22 on our planet is invariably since its formation, and will remain so forever. It is assumed that each of the three scenarios of the birth of the Earth agrees with the different ratio of neon-20 to neon-22.
To determine this coefficient, scientists had to get as close as possible to the depths of the mantle, assembling from the bottom of the Atlantic Ocean samples from the pillow lava – vitreous rock raised from the bowels of the earth and frozen in cold water.
To analyze the gases contained in the tiny vesicles of the basalt, the researchers placed them in a sealed chamber and destroyed, capturing the emissions with a sensitive mass spectrometer.
The ratio of the isotopes that they recorded was much higher than that of the irradiated particles or late accretion models, which bends the scale to the side of the theory of rapid early formation.
This clearly indicates that in the deep mantle of the Earth there is a nebular neon. And given that it is a marker of other sources of gas, hydrogen, water, carbon dioxide and nitrogen also accumulated on the planet at the same time, and this is all the ingredients that we know are essential to life.
-Curtis Williams
The results suggest that in order to absorb these vital compounds for life, the planet must reach at least Mars, before the nebula dissipates, and observations from other systems indicate that it takes between two and three million years.
However, are the worlds around distant stars forming on the same scenario? The data of the ALMA radio telescope array agrees.
ALMA can see protoplanetary disks of dust and gas around some nearby stars, and in some cases dark strips are detected in them.
There are several ways to remove dust from the disk, and one of them is that they form planets in them. It seems that this may be a common way to create habitable planets throughout the universe.
-Judge Mouhahpadhai, lead author of a study from the University of California, Davis
Solving the mystery of Earth formation and its habitability
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