Meet a space researcher who's over the Moon about her work
'I think the Moon is a brilliant thing to work on,' says Museum space scientist Prof Sara Russell. 'Everyone knows what the Moon is, it's something they can all see and have a relationship with.'
The Moon has been a source of interest and mystery for centuries, making appearances in science, art, literature, mythology and religion. Sara has accumulated a vast amount of knowledge of this elusive astronomical body through more than three decades of research.
Now Head of the Planetary Materials Group at the Museum, Sara is fascinated by the formation of the solar system and the evolution of Earth's Moon.
Her work means that, in addition to studying lunar samples and meteorites, she's been actively involved in planning space missions - including the European Space Agency's first mission to the Moon SMART-1 and India's first lunar probe, Chandrayaan-1.
Inspired by the Apollo Moon missions
One of five daughters of doctors, Sara grew up in Manchester in the seventies.
'It was very much the Apollo era,' Sara recalls. 'That was a great inspiration to me as a little girl. I used to love watching news stories about it all. It helped me decide to pursue space science.'
Sara initially thought she wanted to become an astrophysicist. Studying for her degree at the University of Cambridge, she planned to focus on physics, but gravitated towards earth science.
'The people in that department were always very excited to be learning and lecturing about it, and it was really catching,' explains Sara.
One of those people was her lecturer, Jim Long, who introduced her to mineral chemistry.
'Jim told me that if he could do it all over again, he would study meteorites,' she says.
These words gave Sara the final push she needed to follow that route, as she realised she could combine her interest of astronomy and geology.
She completed a PhD in geology and moved to the Open University to study under Colin Pillinger, the lead researcher in the unsuccessful British Beagle 2 mission to Mars.
'He was extremely passionate about what he did and would often get into huge debates with other people about it,' says Russell. 'He was also very invested in my work. I learned a lot from him.'
After working as a research fellow in the USA at Caltech and then the Smithsonian Institution, Sara joined the Natural History Museum in 1998, where she continued studying the formation of stars and planets.
Now a cosmic mineralogist, she specialises in the chemistry of the solar system. Her work focuses on the origin of water in the solar system and geological processes in asteroids.
How do you study the Moon?
Moon samples are rare. Rocks collected from NASA's Apollo and Russia's Luna missions belong to their host space agencies. However, the Museum cares for a handful of lunar meteorites - rock fragments that broke off the Moon after it was hit by an asteroid or comet and then fell to Earth.
Whereas the samples from lunar missions originate from a small area of the Moon's surface, the meteorites come from all over the Moon, allowing scientists to form a better understanding of the overall composition of its surface.
Sara is interested in exploring the surface of the Moon to answer fundamental questions about how the Moon formed.
We now know that a huge, planet-sized body crashed into Earth and smashed a bit out. When it first formed, the Moon was molten due to the large amount of energy involved. As it cooled down, it began to solidify and the lighter, paler crystals drifted to the top. This is the reason why the Moon looks white.
If everything was molten and then crystallised, the white crystals would all have the same composition. However microscopic inspection of its detailed crystal chemistry revealed this is not the case, so this theory is not fully correct.
Sara explains, 'We're now realising that the Moon was probably geologically active for a lot longer than we assumed. The white bit that we thought was pristine has probably been processed and resurfaced.'
What big questions remain about the Moon?
How long has the Moon been geologically active? Why is the far side so different from the nearside? How much water is there on the Moon? These are just some of the questions perched on Sara's lips.
'The Moon is a great laboratory and we could learn a lot if we were on it,' says Sara. 'The Moon and the Earth are twins, so whatever happened on the Moon, such as impacts, also affected the Earth.
'The difference is that Earth's surface has changed over time so the information has been lost. As the Moon's surface is older, it tells us what happened to Earth early on in its history.'
In order to learn about Earth's early history, we need more samples from the Moon.
Beyond the Moon: planning space missions
Besides researching the Moon, Sara also contributes to other space missions, using her meteorite research and expertise.
She is currently involved in a project gathering data from the surface of an asteroid named Bennu. This near-Earth asteroid is thought to be a fragment left over from the formation of the solar system 4.6 billion years ago. The OSIRIS-REx spacecraft launched in 2016 after 16 years of planning, and is expected to return in 2023.
'I will be helping to map the asteroid soon,' says Sara. 'Then the science team can decide what part to sample and bring back to Earth.'
Sara is also working on another asteroid sample-return mission led by the Japanese space agency, JAXA, called Hayabusa2. Launched in 2014, it is expected to survey the asteroid Ryugu and return to Earth in 2020.
Sara says 'Such missions will help us to pair meteorites to their asteroid parents, which will help us to understand the architecture of the solar system.
'We initially thought that all asteroids came from between Mars and Jupiter but now we think some of them might originally have come from the very outermost reaches of the solar system, beyond Jupiter and Saturn. Perhaps they were thrown into the inner solar system in the early time when things were a lot more dynamic, when planets themselves were moving around.'
Sara foresees obtaining samples from the far side of the Moon and many more asteroids over the coming decades, which would help answer a lot of questions about the conditions of the early solar system and how the planets and their satellites formed.