There are a lot of theories about from where did water come on Earth. The answers to this were concluded from lava sampled in 1985 from Baffin Island in the Canadian Arctic.
Dr Mike Drake at the University of Arizona suggested a hypothesis few years back, He stated that water was already present at the surfaces of interstellar dust grains when they accreted to form our planet. Although this hypothesis fitted with all available evidence, it would only be feasible if the adhesion of water to the dust grains was sufficiently strong to survive the harsh conditions in the interstellar dust clouds where planets form and this is exactly what the recent study also says.
According to planetary scientists at the University of Hawaii, water-soaked dust grains present early in the solar system are the actual source of water on Earth.
Linda Elkins-Tanton, director of the Carnegie Institution for Science’s Department of Terrestrial Magnetism stated that evidence is mounting that the planet’s water arrived early, during formation, aboard meteorites and small bodies called “planetesimals.” Studies also suggests that though the planet-forming collisions were so energetic that they led to oceans of magma and widespread melting, even the intense heat would not have dried out the planet completely.
Professor Scott Hyman had already stated how water was formed by nuclear synthesis. He described how the chemical building blocks of water, hydrogen and oxygen, were formed in the “big bang” and in the interior of stars by the process. Planetary probes have stated detecting evidence that water may exist on other bodies in our solar system, however the amount of water present on Earth is the maximum in our solar system. Analysis of water samples from Earth’s deep mantle state that the water has been around on Earth since its formation.
About 4.6 billion years ago, Earth came into form as dust and rocks around the sun collided. Scientists questioned whether the first water molecules were held by the ancient minerals present in the deep mantle, 1,800 miles or 2,900 kilometers deep below Earth’s surface.
The depth is significant in the study and here is why. Lydia Hallis, lead author of the study and a planetary scientist with the University of Glasgow in the United Kingdom, while talking to Live Science stated, “We needed an undisturbed source of mantle from the Earth’s formation.” Earth’s surface has undergone several changes through all these years, but one thing that remains the same is the lava churning in the deep mantle. It has remained the same since the planet took shape.
Hallis said lava samples had to come from deep in the mantle because lava closer to the crust may have erupted and mixed with surface matter. In the search for primordial water, Hallis and her colleagues had to be sure that the minerals they analyzed dated back to Earth’s earliest days, with no contamination from younger rocks.
Finding lava samples in this unspoiled form was not an easy task. Hallis added that hydrogen is present everywhere on Earth. It however cannot be ascertained if the hydrogen that is measured isn’t hydrogen from contamination. In order to know what the researchers measured was something real; took several years.
Scientists were able to study lava’s cool form, which is undisturbed ancient water in basalt, with deep-mantle lava. Hydrogen atoms can tell where Earth’s water came from; particularly, in the percentage between two types of hydrogen atoms, called isotopes. One hydrogen isotope, deuterium, has one neutron, whereas another, hydrogen, has no neutron.
When the number of zero-neutron atoms relative to one-neutron atoms in water’s H2O molecules are compared, they reveal a ratio that is unique to every planet, this also includes asteroids and comets present in our solar system. Earth’s surface water found ratios that favored deuterium in earlier studies. This also sparked theories that water-rich asteroids or comets introduced water on Earth.
The new study however states a different story. The measure of hydrogen isotopes present in dust grains hidden deep inside Earth for billions of years were more. This stated that water-saturated dust embedded itself in the rocky clumps that finally became the Earth we see today.