Professor Ian Crawford has been awarded a Leverhulme Trust research grant to study lunar geology
The grant will fund research into what the Moon may tell us about the history of the Milky Way Galaxy.
The new grant, entitled Assessing the potential of lunar geology as a window into galactic history, was awarded to Professor Crawford and colleagues Dr Pieter Vermeesch (UCL) and Dr Katherine Joy (University of Manchester). Dr Louise Alexander, who obtained both her B.Sc. and Ph.D degrees in planetary science from Birkbeck, will be employed as researcher on the project.
The aim is to study how the flux of galactic cosmic rays (GCRs) impacting the lunar surface has changed with time, and to determine if this can be correlated with the Solar System’s past locations in the Galaxy. The GCR flux is ultimately controlled by astrophysical phenomena (such as the occurrence of supernova explosions and the density of the interstellar medium surrounding the Solar System). The Earth does not retain a good GCR record which could be used for this purpose because its atmosphere and magnetic field greatly attenuate the primary cosmic ray flux, and because Earth’s surface rocks are generally younger than the astronomical events we wish to date. On the other hand, the ancient surface of the Moon, which is completely lacking in an atmosphere and magnetic field, is potentially an ideal recorder of GCR records relevant to reconstructing the past galactic environment of the Solar System.
Figures: (a) Artist’s rendition of the structure of the Milky Way Galaxy (credit: NASA/ESO/ R.Hurt). The Sun orbits the Galaxy once every approximately 200 million years, passing through a wide range of galactic environments; its current position is shown. (b) Close-up of the lunar regolith with astronaut’s boot for scale (credit: NASA); the uppermost metre of regolith is an efficient collector of cosmogenic nuclei produced by cosmic rays produced by astrophysical processes in the Galaxy.
GCRs strike the lunar surface unhindered, where they induce the formation of a range of cosmogenic isotopes (such as 3He, 21Ne and 38Ar) in lunar rocks and soils. The project team will study the concentrations of these isotopes in a range of lunar materials of different ages (including both Apollo samples and lunar meteorites) in order to determine what they may reveal about the history of the Solar System’s passage through the Galaxy. The study will also help identify locations on the lunar surface where future space missions may be able to collect samples that will reveal details of the galactic environment not covered by the existing lunar sample collection.
The Solar System has orbited the Milky Way Galaxy approximately twenty times since it formed 4.6 billion years ago, and during this time it will have been exposed to a wide range of galactic environments. Reconstructing this history would provide astronomically valuable information on the structure and evolution of the Galaxy. In addition, because galactic events may influence life on Earth (for example, an increased supernova rate would lead to a less begin radiation environment at the Earth's surface), knowledge of the galactic environment through time is of interest in assessing the past habitability of our own planet.
Commenting on the award: Professor Crawford said that 'Over the years a number of authors, including myself, have speculated about the value of the lunar geological record in this context. However, as far as we are aware, no really detailed study using actual lunar samples has yet been attempted. The award of this grant now gives us an opportunity to properly assess the value of the lunar geological record for galactic astronomy, which is tremendously exciting. If successful, our project may lay the foundations for a major new scientific field at the boundary of astronomy and planetary science.'