How Earth got its oceans: Hydrogen discovered in samples of asteroid dust suggests more than HALF of our planet’s water came from space rocks
- Researchers studied samples from asteroid Itokawa collected by Hayabusa (1)
- The study revealed the asteroid, thought to be dry, was ‘enriched in water’
- The team suggests asteroid like this could have delivered half of Earth’s water
Scientists have detected traces of water in dust from an asteroid previously assumed to be dry, adding new support for a theory that could explain how Earth’s oceans came to be.
In a new study, researchers from Arizona State University re-examined samples collected by Japan’s first Hayabusa probe back in 2010.
The spacecraft captured roughly 1,500 particles in total when it visited the asteroid Itokawa during the first-ever asteroid sampling mission.
The new analysis revealed a substantial amount of water and hydrogen compositions that are ‘indistinguishable from Earth,’ suggesting water-rich asteroids are far more common than previously thought.
Researchers now say an impact from a similar asteroid in our planet’s history could have been responsible for delivering as much as half of Earth’s water.
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In a new study, researchers from Arizona State University re-examined samples collected by Japan’s first Hayabusa probe back in 2010. The spacecraft captured roughly 1,500 particles in total when it visited the asteroid Itokawa during the first-ever asteroid sampling mission
‘We found the samples we examined were enriched in water compared to the average for inner solar system objects,’ said postdoctoral scholar Ziliang Jin.
Itokawa is what’s know as an S-type asteroid and is thought to have broken off of a larger object that measured at least 12 miles wide.
It’s estimated to be about 1,800 feet long and 700 to 1,000 feet wide, and circles the sun every 18 months.
‘S-type asteroids are one of the most common objects in the asteroid belt,’ said co-author Maitrayee Bose.
‘They originally formed at a distance from the sun of one-third to three times Earth’s distance.’
Despite a series of impacts that occurred to produce today’s Itokawa millions of years ago, the team says the asteroid retained its water.
‘The particles we analyzed came from a part of Itokawa called the Muses Sea,’ says Bose.
The new analysis revealed a substantial amount of water and hydrogen compositions that are ‘indistinguishable from Earth,’ suggesting water-rich asteroids are far more common than previously thought. The particles (shown) are just half the thickness of a human hair
‘It’s an area on the asteroid that’s smooth and dust-covered.’
‘Although the samples were collected at the surface, we don’t know where these grains were in the original parent body,’ Jin adds.
‘But our best guess is that they were buried more than 100 meters deep within it.’
‘The minerals have hydrogen isotopic compositions that are indistinguishable from Earth,’ the Jin said.
The water content of different materials, including primitive Earth and Itokawa, is plotted in the chart above
In the samples, each of which are just half the thickness of a human hair, the researchers found surprising amounts of water.
The discovery suggests these asteroids, assumed to be dry, may be home to much more water than previously thought.
‘This means S-type asteroids and the parent bodies of ordinary chondrites are likely a critical source of water and several other elements for the terrestrial planets,’ Bose said.
‘And we can say this only because of in-situ isotopic measurements on returned samples of asteroid regolith — their surface dust and rocks.
‘That makes these asteroids high-priority targets for exploration.’
WHAT ARE THE DIFFERENT TYPES OF SPACE ROCKS?
An asteroid is a large chunk of rock left over from collisions or the early solar system. Most are located between Mars and Jupiter in the Main Belt.
A comet is a rock covered in ice, methane and other compounds. Their orbits take them much further out of the solar system.
A meteor is what astronomers call a flash of light in the atmosphere when debris burns up.
This debris itself is known as a meteoroid. Most are so small they are vapourised in the atmosphere.
If any of this meteoroid makes it to Earth, it is called a meteorite.
Meteors, meteoroids and meteorites normally originate from asteroids and comets.
For example, if Earth passes through the tail of a comet, much of the debris burns up in the atmosphere, forming a meteor shower.