Space rock research could reveal origins of Earth’s oceans

Published: 13 November 2019

The return of a space probe bearing samples from a distant asteroid is being eagerly anticipated by researchers from the University of Glasgow and Curtin University in Australia.

The return of a space probe bearing samples from a distant asteroid is being eagerly anticipated by researchers from the University of Glasgow and Curtin University in Australia.A portrait of Dr Luke Daly from the School of Geographical and Earth Sciences

Scientists from the School of Geographical and Earth Sciences will receive three miniscule precious pieces of the asteroid Ryugu when the uncrewed Hayabusa2 mission returns to Earth late next year after six years in space.

They plan to use a sophisticated technique known as atom probe tomography, or APT, to examine the samples and learn more about how the Earth’s oceans were formed.

The samples will be provided by JAXA, the Japanese Aeronautical Exploration Agency, which launched Hayabusa2 in December 2014. Hayabusa2 arrived at Ryugu on June 2018 and later dropped a lander and two rovers onto its rocky, icy surface. In February this year, it fired an impactor into the asteroid, allowing the rovers to collect samples from beneath Ryugu’s surface.

Hayabusa 2 began the return leg of its journey this week, and is expected to touch down in Woomera, Australia in December next year. JAXA will share tiny slices of the samples collected by the mothership with research partners around the world, including planetary scientists from the University of Glasgow.

Dr Luke Daly of the University of Glasgow’s School of Geographical and Earth Sciences is the lead academic on the atom probe project. He will work with colleagues from Curtin University, in Australia to conduct the research.

The atom probe tomography equipment at Curtin University will allow the team to slice single atoms from the samples using a pulsed laser. Measuring the time it takes for those single atoms to move from the sample to a detector will determine their mass and charge and help the team build up, atom-by-atom, a full picture of the exact chemical and isotopic composition of the samples.

The team hope that their analysis will provide critical new insights into the early history of the solar system, particularly how water accumulated on the still-forming Earth.

Dr Daly added: “When the Earth began to take shape, water was only present in the our region of the solar system in the form of gas, which would have been blown away from the proto-Earth out by the early solar winds meaning Earth formed dry, so exactly where our oceans came from is still a bit of a mystery. One suggestion is that it was carried here on comets and asteroids, but recent measurements show that the composition of those potential sources don’t match that of the Earth’s oceans – there has to be another source which also contributed water.

“What we’re hoping to explore is the possibility that this missing water could have been seeded by the Sun itself. The APT process will give us an extraordinary level of detail about what the three samples we’ll receive from JAXA are made from and how they’ve been affected and altered by exposure to solar wind – radiation from the sun - while they were sitting on the surface of the asteroid.

“We know that the hydrogen ions from solar wind irradiates rocks and their constituent minerals, which generates water. Being able to physically interact with the Hayabusa2 samples with APT will provide us with a wealth of new information about the water in the asteroid and how it was formed. We hope that will help us get closer to unlocking the mystery of how our oceans were created.”

Dr Daly will spend time over the next year at APT facilities at the University of Oxford, in Australia at Curtin University and the University of Sydney, fine-tuning the APT process to ensure the research team maximise the potential of the samples from Hayabusa2.

He added: “It’s an enormous privilege to be working with JAXA and our partners in the UK and Australia to do this research, and we’re very grateful for the support of our funders. We’re excited to begin the analysis of the samples in early 2021.”

The researchers expect to begin work on the samples within three months of their arrival back on Earth. The preliminary work for this partnership is funded by the Science and Technology Facilities Council (STFC).

First published: 13 November 2019