- Our Sun is the surprising source of our planet’s abundant water supply, study finds
- Scientists analyze fragments of an asteroid that returned to Earth in 2010
- They say grains of extraterrestrial dust carried water to Earth as our planet formed
Water covers about 70 percent of Earth’s surface, but how it became so abundant on our planet has long puzzled scientists.
Now, an international team of researchers has suggested that the Sun is a ‘surprising potential source’ of Earth’s water, based on asteroid analysis.
Researchers point to the solar wind – a vicious stream of charged particles from the Sun that is composed largely of hydrogen ions.
They say that about 4.5 billion years ago, the solar wind created water within particles of space dust that hit Earth in the form of a spectacular meteor shower.
An artist’s impression of a C-type asteroid and space dust raining down on Earth at the beginning of its formation. Space dust carried the water that formed Earth’s oceans
Itokawa space weathering scene: An artist’s impression of the space weathering process, showing solar radiation affecting space dust on the surface of the Itokawa asteroid
What are solar winds?
The solar wind is created by the outward expansion of plasma (a collection of charged particles) from the Sun’s corona (outermost atmosphere).
This plasma is constantly heated to such an extent that the Sun’s gravity cannot stop it. It then travels along the Sun’s magnetic field lines that extend radially outwards.
As the Sun rotates (once every 27 days), it spins its magnetic field lines over its polar regions in a large rotating spiral, creating a constant stream of ‘wind’.
Solar winds still exist today, and travel at speeds of up to 560 miles per second (900 km per second) and temperatures of 2 million degrees Fahrenheit.
Early in the formation of the Solar System, the water in dust grains was produced by a process called space weathering, where solar winds changed the chemical composition of the grains to produce water molecules.
Study author Dr Luke Daly at the University of Glasgow explains, ‘Solar winds are mostly currents of hydrogen and helium ions that continuously flow from the Sun into space.
‘When those hydrogen ions hit an airless surface such as an asteroid or dust particles in space, they penetrate a few tens of nanometers below the surface, where they can affect the chemical composition of the rock.
‘Over time, the ‘space weathering’ effect of hydrogen ions can strip enough oxygen atoms out of the material in the rock so that H2O – water – is trapped within the minerals on the asteroid.’
Dr Daly thinks that this process, and the resulting formation of the oceans, preceded the formation of Earth’s magnetosphere – the region around Earth that is controlled by the planet’s magnetic field.
An artist’s impression of the space weathering process, showing solar radiation affecting dust particles floating in space
Different Types of Asteroids from the Solar System
With many letter-based systems developed, asteroid classification has proved controversial.
According to NASA the three main types are labeled C, S and M.
C-type (chondrite) Asteroids are the most common in the Solar System and are likely to consist of clay and silicate rocks.
They are darker in color than other asteroids and the most ancient objects in the Solar System – those that predate its birth.
S-Type (Stone) Asteroids are composed of silicate material as well as nickel-iron and are the most common visitors to Earth of the asteroid type.
S-type asteroids orbit closer to the Sun than C-types.
M-Type (Nickel-Iron) Asteroids vary depending on how far they form from the Sun.
Some are partially melted by the sinking of iron in the center and forcing the volcanic lava to the surface.
“As far as I know, there is no clear consensus on when the Earth’s magnetosphere formed,” he told MailOnline.
‘But this collapse of small dust grains and large asteroids that carried Earth’s water probably occurred within the first 5-15 million years of the history of the Solar System as Earth was gaining the last bit of its final mass, so possibly That was long before the magnetosphere. Established.’
Earth is very water-rich compared to other rocky planets in the Solar System.
About 71 percent of Earth’s surface is covered by water, and Earth’s oceans account for about 96.5 percent of all Earth’s water—but scientists had long wondered about its exact source.
One current theory is that water was carried to Earth in the final stages of their formation on C-type asteroids 4.6 billion years ago – the water-rich, primitive bodies in the asteroid belt.
‘However, previous testing of the isotopic “fingerprints” of these asteroids found that they did not, on average, match the water found on Earth, meaning there was at least one other unaccounted for the source,’ in Curtin. Study author Professor Phil Bland from the University of Perth, Australia.
‘Our research shows that the solar wind created water on the surface of tiny dust particles and that this isotopically lighter water probably provided the rest of Earth’s water.’
The new results are based on a microscopic atom-by-atom analysis of microscopic fragments of an S-type near-Earth asteroid, known as Itokawa, that is still in orbit in space today.
Itokawa’s samples were collected by the Japanese space probe Hayabusa and returned to Earth in 2010.
The researchers used an advanced analytical process called nuclear probe tomography to examine the samples from Itokawa.
The new theory is based on a microscopic atom-by-atom analysis of the microscopic fragments of an S-type near-Earth asteroid known as Itokawa. Pictured is a scanning electron microscope image of the Itokawa piece
Another scanning electron microscope image of the Itokawa piece. These pieces are about the width of a human hair