Australian National University scientist Barbara Frasl is studying matter from the Sun obtained from soil samples from the Moon to get hints on the evolution of the solar system.
Frasl, of the Research School of Earth Sciences, is measuring the isotopic composition of oxygen embedded in iron-nickel grains in lunar soil samples retrieved in NASA’s Apollo missions.
The tiny metallic grains preserve particles from the Sun that were implanted in them when our star’s corona, or outer atmosphere, ripped into space as the “solar wind”, lashing the Moon.
It is thought that the corona reflects the composition of the solar nebula – the cloud of gas and dust from which the solar system took shape about 4.5 billion years ago.
Scientists are still arguing about the evolution of the solar system. Differences in the chemical and isotopic composition of the Sun, which accounts for 99.8 per cent of the mass of the solar system, and the planets enable them to test competing hypotheses.
Some of Frasl’s metallic grains probably have their origin in meteorites or asteroids that struck the Moon recently in geological terms. The samples contain more of the stuff of the Sun than do rocks and sediments from the Earth, which is partly shielded from the solar wind by its magnetic field.
"The Moon has no magnetic field, and when these energetic particles from the Sun hit it, they are implanted into the lunar surface," she says.
Frasl is analysing the fine grey grains on the ANU’s state-of-the-art SHRIMP (sensitive high resolution ion microprobe) mass spectrometer. She is working on samples as small as 50 millionths of a metre in diameter.
She is measuring the concentrations of the three oxygen isotopes – oxygen-16, the most common form of the element, oxygen-17 and oxygen-18.
Her results will complement data from NASA’s Genesis Project. The Genesis spacecraft collected elements from the solar wind in a 3-million-kilometre mission between 2001 and 2004. The oxygen isotope composition of the samples was a major objective of the mission.
As an earth sciences undergraduate student in Austria, Frasl became increasingly fascinated by planetary science. She was attracted to the ANU by the Planetary Science Institute, which drives collaboration between the RSES and the Research School of Astronomy and Astrophysics.
"This degree of collaboration between earth sciences and astronomical science is unique in the world" she says.