Life on Mars?

In his day job, Xinran Liu focuses on the direct detection of dark matter and it was this that led him to a fascinating project for children. His story starts with the idea that, so far, all of the evidence for the existence of dark matter comes from astronomical sources. But what scientists really want to be able to do is detect dark matter directly in a laboratory setting.

Liu explains, ‘astronomical evidence over the last several decades has given us a very specific set of properties of what dark matter might be, if it exists. And we think the current best candidate for dark matter is something called a weakly interactive massive particle, or WIMP for short.

'Dark matter may very well not be a weakly interacting massive particle or WIMP, but if dark matter does interact via the weak force, we may be able to detect it. If it doesn't interact via the weak force, we'll probably never see it, at least not in my lifetime. So in short, the success of dark matter detection requires dark matter being a little wimpy, as we always say.

‘We know it doesn't interact via electromagnetism, because it would be very easy to see. We know it doesn't interact via the strong force – there is lots of data that shows no evidence for that. So the only things left are via gravity, which is where all of our astronomical evidence is from, or the weak force .’

The exploration of the weak force is described by Liu using the example of the neutrino. Discovered in the 1950s, it is a ghostly particle that is invisible to the eye and to the touch, but billions travel through each of us per second, never interacting with our bodies. ‘However’, he says, ‘we've gotten quite good at detecting these kinds of things via the weak interaction, so that's why we're building these large detectors looking evidence of dark matter - usually underground.’

Signal versus noise

Like many modern pursuits this kind of research depends on data. In this case data from dark matter detectors, which started from humble beginnings in the 80s. They need to be deep underground, because ‘in Edinburgh University for example,’ says Liu, ‘even in the basement here, we'll be bombarded by cosmic radiation coming from our sun and space. And that would be a humongous background noise and it would swamp out any chances of us looking for dark matter. So scientists have always tried to go underground, at least a few hundred metres.’

That’s where the site for this schools initiative comes in - an active polyhalite and salt mine in the northeast coast of England, near the town of Whitby, called Boulby. The mine is 1.1 kilometres deep and so an ideal place to do dark matter research because the background cosmic radiation is reduced by a factor of 1,000,000.

Detection is about noise to signal ratio. Says Liu, ‘We're looking for an interaction that is very rare, that maybe only happens once or twice a year. There are broadly three ways to look for dark matter: make it, shake it or break it. You “make it” in something like Hadron Collider at CERN, where you smash things together and you try to make dark matter. You can “break it” in experiments on, for example the International Space Station designed to look for dark matter interactions. In space they can interact with the anti-components and have annihilation signatures.

‘But by far the most powerful has been to “shake it”, which means you just build a large target and you let the dark matter smash into it deep underground.

Like the lab at Boulby and the other detector Liu works with – the Lux ZEPLIN detector, a multi-ton scale detector based at the Sanford Underground Research Facility in South Dakota. ‘It is calculated that the central cubic metre of the LUX ZEPLIN detector will be the most radioactively quiet place in the universe,’ says Liu, ‘which is pretty fun’.

Where do the students come in?

The story now moves from theoretical physics to space travel, because the Boulby Underground Laboratory, run by UKRI’s Science and Technology Facility’s Council with support from the mine, ICL-UK) is analogous to the Martian environment.

A few years back they discovered that even in this harsh environment there were still living things present - in salt – in a place that last saw the sun 230,000,000 years ago. Similar life could have lived on in the salt deposits on Mars, which is exactly what the Mars Rovers look for, and is why NASA and ESA have been using Boulby as a test facility for the next generations of Mars Rovers, drones and other instruments.

‘So that's really exciting. And it's always fun when the scientists show up to do that,’ says Liu, ‘but they only use it for two weeks a year. It's just empty the rest of the time, which I always thought was a shame. So we developed this project called Remote3, which stands for “Remote sensing by Remote schools in Remote environments” for schools in Scotland targeting 11- to 14-year-olds.’

The task

Students are sent a Lego Inventor kit along with the Lego Education Pack, which gives them almost 2,000 pieces of Lego with a programmable core, motors, wheels and sensors. They're asked to do what the NASA and ESA teams are trying to do, which is explore the Mars Yard and complete some tasks, like sampling the water, finding some specific-coloured rock (a yellow rock may indicate sulphur content, for example), and navigate the terrain.

‘We aim to set so many tasks that it is not really possible to complete within the time that they have,’ says Liu, ‘so it's up to each school to time manage their and optimise their design to complete as many tasks as they can. It really gives the freedom to the students to design their Rovers however they want to complete whatever tasks they see is most important.

‘On the day they have the time to explore the Mars Yard and then they present the results to their parents and peers in school. It helps them learn teamwork, time management and presentation skills. But it's the coding of the Rovers to do the exploration that we're most excited about.’

As to the platform, they opted for Lego in part because it comes with a range of sensors and motors. Students also have the option of adding an optical camera to each Rover so the schools can see their Rover exploring and, if there're errors, they can correct their code, live on the spot.

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This is based on a coding language called Scratch, which you can code using the drag and drop block language, but can also be converted to Python script. So if the teams were feeling good about their coding skills and wanted to learn Python it's very easy to convert.

‘Also,’ says Liu, ‘we're working with children, Lego is a designed for the age group we are working with so meets all the safety requirements for our project.

As to the timescales, Liu explains: ‘We send all Lego out in February, March and students have essentially 16 weeks. They start with just two boxes of raw pieces of Lego, the code, and the core and we send them a mission pack. We give them the layout of the terrain and different checkpoints. Once they can go from checkpoint A to B then they can restart from checkpoint B all the time without having to go for the whole loop because we discovered it's difficult to program the Rover to do 30 minutes of movement.

Each school has a dedicated mentor with someone from either STFC or Edinburgh University, including graduates, PhD students and postdocs. Their dedicated mentor meets with them weekly, keeps them on track with their build, and they are also on site to check it all works as designed – after all, Lego can disassemble in transit.

In the Mars Yard the students have a day to test their design. And then if there're any problems, their mentors can make some last-minute adjustments. And then there is one exploration and celebration day where each school has 20 minutes to carry out the tasks.

Inclusion considerations

As to the competitive element, Liu comments; ‘we didn't want to have a direct competition between each school because research suggests that this could reduce female uptake, and we're very keen on working from underserved communities, each team is competing against time rather than other people.’

Liu has had a lot of teacher testimony. Teachers from Lockerbie Academy, for example, found that all the people who initially signed up were female students, which they were not expecting.

‘That was a welcome surprise,’ says Liu. ‘More feedback came from Wick High School, which is in a very socially and economically deprived area - or a large proportion of the students come from those areas. We're very keen to work with them because we're deliberately asking the teachers to engage students who are not actively engaged in STEM. Because it's kind of robotics and science-fictiony, teachers have told us that it’s been good to break down barriers, to engage people who might otherwise not be big fans of doing math or science.’

Rolling it out

Initially promotion was done through a network in Scotland called Sputnik, which consists of nearly a thousand primary and secondary schools, and the public engagement team at Edinburgh University. The team selected schools based on geographical location, remoteness, which has a high correlation with social and economic deprivation. This is part of STFC’s Wonder Initiative, which aims to work with schools and pupils, particularly from the bottom 40 percentile of socioeconomic deprivation.

‘The next phase includes rolling this out to schools in England,’ says Liu. ‘We're trialling with ten. We had to pause due to COVID because there were no in-person classes and it's hard to build the Rover together as team. But the plan for the next phase is to expand it to 30 schools and then to more nationwide.

‘We are expanding slowly, encroaching South. The final goal would be to expand it to all schools in the UK.’

The future

What is Liu’s motivation? ‘ I've always been very keen on doing public engagement and I heard this great saying, which is science not talked about is science not done, which I think is really true and more important now than ever.’

‘Scientists should bring their research directly to the public and discuss it that way. And I think it also makes researchers better at presenting their data, and better at thinking about their research in the grander scheme. I've always had this passion to do stem engagement with underserved groups because I sit on the EDI Committee, the Equality Equity Diversity Inclusion Committee here at Edinburgh.

‘We study the numbers of, you know, for example, women, taking physics, but at some point you need to do the public engagement, the early work, engaging people at a much younger age.’

‘It’s critically important that we inspire the next generation of children because physics is always looking for the next Einstein or Newton to take over, to revolutionize the field. We don't want to miss out the next Einstein because they weren't given any access or opportunity to attend science fairs or something like that.

‘I think we've reached this stage of kind of technological adolescence right now, where technology is advancing ridiculously fast and we're struggling to keep up. And then I have this theory that in 100 years’ time, if we can survive into technological maturity, we'll be a very successful species for a much longer time. But over that next 100 years, there will be some of the toughest challenges.

'We need to get the smartest, brightest and most enthusiastic of the next generation into whatever jobs they will need to do. The most encouraging thing from this whole thing is how remarkably great 11-year-olds are at coding, terrifyingly so, in fact. So from that, I am pretty confident that we can overcome those challenges. ‘