Research Fellow, Richard Greenwood, is researching what formed the Moon and when water arrived on the Earth. This will provide an understanding of whether there is water on exoplanets in nearby solar systems. Open University scientists have discovered that most of Earth’s water was present before the giant impact, which created the Moon, and not delivered later by small asteroids and comets as previously thought. This suggests liquid water can survive catastrophic impacts and could be abundant on exoplanets, making it more likely that life exists beyond our Solar System.
Research led by scientists from SSERVI’s International Partners at The Open University (OU) and an international team of academics, published March 28, 2018, in Science Advances, has discovered that water was present on Earth at an early stage in its evolution and survived the giant impact, which formed the Moon. This catastrophic impact about 100 million years after the Solar System formed*, resulted in the two colliding planets completely merging to create the Earth-Moon system we have now. We know exoplanets – planets in other solar systems – experienced similar high-energy collisions early in their evolution so liquid water, and therefore life, is more likely to be present on their surfaces.
Funded by the Science and Technology Facilities Council (STFC) in the most comprehensive study of its kind, scientists compared the oxygen composition** of lunar rocks brought back from all six of the NASA Apollo landings on the Moon with volcanic rocks from the ocean floor here on Earth. They detected only a small difference between the lunar and terrestrial rocks. This demonstrates how efficiently the two colliding planets mixed, and also places strict limits on the types of material that could have been added to the Earth afterwards. If most of the water on Earth had arrived after the collision, we would expect the lunar and terrestrial rocks to have distinctly different oxygen compositions. This suggests that liquid water on Earth must have existed at an earlier stage, prior to the Moon-forming impact.
Lead author of the research, Richard Greenwood from the OU, explains: “Because water is such a vital ingredient for life, we rightly see it as precious. Our research shows that water is also extremely resilient and can survive an event as catastrophic as two planets colliding. What’s even more fascinating is that, because this worked for the Earth and the Moon, it must also work for planets beyond our Solar System. Exoplanets with water on their surfaces may be much more common than we previously thought. And where there’s water, there could also be life!”
The research, ‘Oxygen isotopic evidence for accretion of Earth’s water prior to a high energy Moon-forming giant impact’, is published in Science Advances.
*The formation of the solar system has been dated as 4,567 million years ago.
**Oxygen isotopes: oxygen atoms with a variable number of neutrons.
Interested in reading more? Check out the blog about this paper written by Richard Greenwood for the non-specialist.
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Posted by: Soderman/SSERVI Staff
Source: SSERVI UK team