Around 70% of Earth’s land surface is covered by water, though scientists have long puzzled over how this happened.  

A team of international researchers has now suggested, using asteroid analysis, that the Sun might be the source of water for the Earth. 

The researchers point to solar wind – a vicious stream of charged particles from the Sun largely made of hydrogen ions.

According to them, around 4.5 billion year ago, the solar wind produced water from grains of space dirt. These were then smashed into Earth in a spectacular meteor shower. 

An artist’s impression of C-type asteroids and space dust raining down on the Earth early in its formation. The space dust carried water that formed the Earth’s oceans

A artist’s impression depicting C-type asteroids & space dust falling down upon the Earth at an early stage of its formation. It was the space dust that carried water which created Earth’s oceans.

Itokawa space weathering visualisation: An artist’s impression of the space weathering process, showing solar radiation affecting space dust on the surface of the Itokawa asteroid

Itokawa Space Weathering Visualization: Artist’s impression showing the process of space weathering. This shows solar radiation and space dust on top of the Itokawa Asteroid.

What are SOLAR WINDS? 

Solar wind is formed by outward expansions of plasma, a mixture of charged particles from the Sun’s outermost atmosphere. 

It is heated continuously to the point at which the Sun’s gravitation can’t keep it down. This plasma travels then along the Sun’s magnetic fields that radiate outward. 

When the Sun revolves once every 27 days, it windes up its magnetic field lines over its polar regions to create a large rotating circle that produces a continuous stream of ‘wind.


The sun’s energy is still available today. It can reach speeds of 560 miles per seconds (900 km/sec) and maintain temperatures up to 2 million degrees Fahrenheit. 

Space weathering was a method by which water from the dust grains became water during the creation of the Solar System. This process involved changing the chemical composition of grains so that water molecules could be produced.

‘The solar winds are streams of mostly hydrogen and helium ions which flow constantly from the Sun out into space,’ explains study author Dr Luke Daly at the University of Glasgow. 

“When these hydrogen ions touch an airless surface, such as an Asteroid or a Spaceborne Dust particle, they penetrate several tens to nanometres under the surface. They can then affect the chemical structure of the rock. 

‘Over time, the ‘space weathering’ effect of the hydrogen ions can eject enough oxygen atoms from materials in the rock to create H2O – water – trapped within minerals on the asteroid.’  

Dr Daly thinks this process, and the resulting formation of oceans, happened before the formation of Earth’s magnetosphere – the area around Earth 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

Artist’s impression showing the effects of solar radiation on dust particles in space.


The controversial issue of steroid classification is well-documented, and there have been many letter-based methods. 

NASA labels the types C, S and MM as their main type.

C-type (chondrite)Asteroids, which are most frequent in the solar system’s solar system, likely contain clay and silicate rock.

These asteroids are more dark than others and they represent the oldest objects in our solar system, dating back to the sun’s birth.

S-type (stony) asteroids are made of silicate materials as well as nickel-iron and are the most common visitors to the Earth of the asteroid types.

S-type asteroids are closer to the sun that C-types. 

M-type (nickel-iron) The formation distance of asteroids varies depending on their proximity to the sun.

These are partly melted and have iron in the middle, forcing volcanic lava up to the surface. 

MailOnline was told by he that there’s no consensus as to when Earth’s magnetic field formed.

“But the infall of small dust grains, large asteroids and that provided Earth’s water likely occurred within 5-15million years of the solar system’s history. Earth was receiving its last mass. This was probably long before the establishment of the magnetosphere. 

Earth has a high water content compared with other rocky planets within the Solar System. 

About 71 per cent of the Earth’s surface is water-covered, and Earth’s oceans hold about 96.5 per cent of all Earth’s water – but scientists had long puzzled over the exact source of it all. 

An existing theory is that water was carried to Earth in the final stages of its formation 4.6 billion years ago on C-type asteroids – water-rich, primitive bodies in the asteroid belt.   

‘However, previous testing of the isotopic “fingerprint” of these asteroids found they, on average, didn’t match with the water found on Earth meaning there was at least one other unaccounted for source,’ said study author Professor Phil Bland at Curtin University, Perth, Australia. 

“Our research shows that water is created by the solar wind on tiny dust grains, which may have provided water for the remaining water in the earth’s surface.”   

These new findings are the result of a careful atom-by atom analysis of tiny fragments from an S-type, near-Earth asteroid called Itokawa. It still orbits in outer space.  

Itokawa samples were taken by Hayabusa, a Japanese space probe. They returned them to Earth in 2010.

Itokawa samples were examined using a sophisticated analytical method called Atom Probe Tomography. 

The new theory is based on a meticulous atom-by-atom analysis of miniscule fragments of an S-type near-Earth asteroid known as Itokawa. Pictured is a scanning electron microscope image of the Itokawa fragment

This theory was based upon a detailed atom-by atom analysis of tiny fragments from an S-type near Earth asteroid called Itokawa. A scanning electron microscope image shows the Itokawa fragment.

Another scanning electron microscope image of the Itokawa fragment. These fragments are about the width of a human hair

Another image from the scanning electron microscope of the Itokawa segment. These fragments have a width similar to a human’s hair.

Atom probe photography allowed for the measurement of each atom in the grain’s atomic structure. It also enabled the detection and identification of individual water molecules.  

Professor Bland explained that Curtin University’s world class atom probe imaging system allowed for an unprecedented look at the Itokawa dust grains’ surface in the 50-nanometer range.

The researchers found that water had been produced below the surface by Itokawa’s dust-sized grains through space weathering. 

According to the research team, dust grains had enough water in them that they could hold approximately 20 litres of water per cubic meter of rock. 

Scanning electron image of a segment of an Itokawa fragment being prepared into a needle like shape for atom probe tomography analysis

A scanning electron image showing a section of the Itokawa fragment that was made into a needle-like shape for Atom Probe Tomography Analysis

Researchers suggest that this water-rich dust could have fallen onto Earth as part of Earth’s delivery of oceans.

Dr Daly stressed the fact that space dust carrying ocean-forming water to Earth was not on asteroids. Rather, it was floating around in space and then raining down upon Earth early in the morning in the form a stunning shower. 

They could have. space dust on the surfaces of asteroids that smashed into the Earth that would have brought water too – but only a small amount. 

‘There is a lot more dust that is free floating in space at that time which, should enough of it fall onto the Earth would have a much bigger impact on Earth’s oceans,’ Dr Daly told MailOnline. 

A view of the water content of one of the fragments of the Itokawa asteroids used in the study - the grey spheres mark the surface of the grain that was covered in a protective layer of chromium, and the blue spheres show the distribution of water in the Itokawa fragment where an increase in the concentration of the water at the grains surface can be seen. The image was created using atom probe tomography

View of the Itokawa Asteroids’ water content. One of the Itokawa pieces was used for the study. The grey spheres are the grain’s surface, which has been protected with a layer of chromium. Blue spheres depict the distribution and concentration of water in one fragment of Itokawa. Image was taken using atom probe photography

The team claims that NASA’s Artemis Astronauts might be able, thanks to these new discoveries, to extract fresh water from lunar dust later in the decade.   

Dr Daly explained that one barrier to future space exploration is how astronauts could get enough water without carrying any supplies. 

Itokawa’s water was created by the same process of space weathering that occurred on other planets. This means that astronauts might be able extract fresh water from dusty planets like the Moon.

“NASA’s Artemis Project is aiming to create a permanent lunar base. It would be a valuable and enormous resource to help achieve this goal if the lunar surface had a comparable water reservoir, as discovered on Itokawa by solar wind.

This study was published in Nature Astronomy. 

An illustration of the SpaceX Starship human lander design that will carry the first NASA astronauts to the surface of the Moon under the Artemis program in 2024

A SpaceX Starship illustration showing the human lander design for the SpaceX Starship. This will be used to transport first NASA astronauts to lunar surface in the Artemis program.

Explained: What is the difference between an asteroid and a meteorite?

This article is about asteroid A large amount of rock that was left from the collisions and early solar system. They are found between Mars and Jupiter within the Main Belt.

Comet A rock that is covered with ice, methane or other compounds. Their orbits lead them further from the sun.

meteor It is what Astronomers call an “flash of light” in the atmosphere, when debris has burned up.

The debris is also known as “a” meteoroid. Many of them are small enough to be vapourized in the atmosphere.

A meteoroid that makes it to Earth is known as a “A” Meteorite.

Asteroids and comets are the usual sources of meteoroids, meteoroids, or meteorites.

One example is that a comet’s tail passes by Earth, and much of it burns in the atmosphere. It forms a meteor Shower.