Meteorites were not the main source of water on Earth
(ORDO NEWS) — Deep oceans cover most of our planet, but the origin of this vast body of water is not entirely clear. A popular hypothesis is that water was brought to Earth by ice-rich meteorites. But a new article claims that the small bodies that fell on the young Earth (namely, the so-called achondrites) were too dry for this.
Water covers 71 percent of the Earth’s surface, with an average ocean depth of almost four kilometers.
In general, our planet contains more water – primarily in a liquid state – than would be expected at its size and distance from the Sun.
It is generally accepted that water was brought here at the early stages of the development of the Earth during the fall of other space objects.
It could be a huge body that collided with the planet and caused the formation of the Moon (megaimpact), and many small objects that at first actively bombarded the Earth.
The object of the study was achondrites, a fairly common type of stone meteorites that do not have characteristic rounded inclusions – chondrules.
This absence is associated with the complete or partial melting of the meteorite material.
Achondrites were actively falling to the young Earth after the formation of the solar system about 4.5 billion years ago. They were in a molten state due to strong radiation.
In total, seven samples of achondrites have been studied, originating from at least five different planetesimals – celestial bodies that rotated in the solar system at the beginning of its history.
At the same time, these meteorites hit the Earth quite recently.
To begin with, scientists had to carefully remove water from the surface layers of these meteorites – using roasting in a furnace and a powerful pump.
This moisture got into the achondrites already on Earth and would interfere with measurements.
Next, the authors used various physical techniques to measure the content of magnesium, iron, calcium, silicon and, of course, water in the samples.
It turned out that in such meteorites there was extremely little water.
Moreover, achondrites turned out to be one of the “driest” extraterrestrial minerals: the water content in them did not exceed two micrograms per gram.
It is noteworthy that among the studied samples there are those formed both in the inner and outer parts of our planetary system.
“It is generally accepted that if an object comes from remote areas of the solar system, then it necessarily contains a lot of water.
Our article strongly refutes this. When the substance of a meteorite melts, there is no moisture left in it, ”said one of the authors, Sune Nielsen.
According to scientists, their result refutes the hypothesis that meteorites falling to Earth became the main source of water and filled the oceans.
These conclusions can also be useful for studying the problem of abiogenesis – the spontaneous generation of life, as well as when searching for traces of life on other planets.
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