The water wasn't doing the trick, and the Golden Syrup was a bit of a problem. The Martian lava flows were behaving inconsistently and even the PhD student in the classroom couldn't help.
Then the physics teacher Denise Gault found they had some glycerol after all and, reluctantly, filled the waiting beakers in front of the class of grammar school girls. She was reluctant because last time the pupils at Cambridge House in Ballymena, Co Antrim, Northern Ireland, did one of their Marsology (the study of Mars) experiments, they had used up most of the available local supplies.
The PhD student, Catherine Donnelly from Queen's University Belfast, is involved in the Pupil Researcher Initiative, a huge and imaginative project which has been running for more than two years. Funded by the Engineering and Physical Sciences Research Council and the Particle Physics and Astronomy Research Council, it taps into the supply of PhD researchers at universities and pays them to go into schools. They help pupils working on research briefs devised by the Centre for Science Education at Sheffield Hallam University.
Back in Ballymena, an ill sectarian wind may be blowing outside but none of it penetrates the classroom. Pairs of girls are working with quiet concentration - calculating how lava, flowing from one of the many volcanoes on Mars, might behave.
It's an experiment suggested in the brief and which they have worked on before. They've set up slopes at various angles - some with a smooth cardboard surface and some with rough emery paper. Using manual droppers and burettes, they're timing single drops of glycerol as they course down the inclines.
Some of the girls are working with glycerol diluted to different viscosities; others have heated it so that the behaviour of the drops at different temperatures can be observed. Computer screens help to provide exact temperature readings and to plot the results, which were mostly consistent.
But what has this practical but earthbound experiment got to do with Mars? This particular research brief required the pupils to suggest what kind of samples a space probe should look for on and beneath the surface of Mars.
These samples would provide evidence of the geology of Martian volcanoes. So the aim was to examine how lava behaved under variable conditions on Earth. (Molten lava being unsuitable for classrooms, glycerol was substituted. ) That knowledge could then be applied to getting and analysing the samples from Mars and using them to test the assumption that volcanoes were formed in the same way on Mars as on Earth.
As is often the way in Northern Ireland's traditionally excellent grammar schools, the girls talked a touch reticently about their results and about the value of having another person, who was not a teacher but knew a lot more than them, in the classroom.
"Catherine Donnelly talked to us about volcanoes to begin with and then she helped us to work the experiment out for ourselves," said Joanne Carruthers. "Without her we wouldn't have been able to do it quite so well. Even though I'm not a scientist, I found it interesting. Science turns me off because it doesn't seem to be much to do with life. It's theoretical. But this was about exact things that go on."
Louise Hanna also admitted she wasn't keen on science but she liked doing the experiments. "If we got stuck Catherine helped us to understand why. She was easy to talk to."
Catherine Donnelly is in the final year of her PhD at the highly ranked physics department at Queen's University. As she is interested in teaching as a career, she liked the idea of being involved with a school. At first, she found trying to find relevant experiments for the class daunting, but once they were under way it was exciting.
What the brief did for the girls, she felt, was to "help them to develop experimental procedure - to explore different techniques in a situation you don't know about". The pupils were keen to know about what she did as a researcher, and valued a contact who was at university. "It was an advantage not being a scary person, but an in-between person," she said.
But there's nothing scary about Denise Gault who has overseen the project. She first heard about it on an in-service training course and she liked the idea of helping to change GCSE coursework. "PRI offered several briefs, but the girls chose the Marsology one themselves," she said. She was offered two research jobs - each coming for one day a week. Denise Gault used the researchers differently - Catherine Donnelly on the experiment with a large group and Caroline Greer with smaller tutorial groups.
"Moving from the brief to the experiment took so long that I couldn't have done it on my own, even with the small classes we have here," Denise Gault said. The main benefit from the PRI for her was that in the summer she had a bursary of Pounds 1,000 which allowed her to go to St Andrews University for a fortnight to help in research projects looking at how cool stars evolve.
She found the experience a tremendous opportunity, but she wouldn't have been able to take it up without the support of the headteacher and the head of science Billy McClune.
At Sheffield, a larger comprehensive school, Westfield Mosborough, has been involved in the PRI from the start and is trialling one of the new research briefs.
Andy Bullough, head of science, likes the way the briefs have been given a slight role-play element - something which is rare in science. They have had several PhD researchers in the school, although not working on specific briefs as in Ballymena. Andy has taken two researchers and some pupils for an astronomy weekend in the Lake District. "Children don't know what scientists are like," he says. "They think of them as wearing white coats and having spiky hair. They were surprised to find that they weren't as removed from real life as they expected. One child said to a researcher, 'You're quite normal really', and another began to think seriously about switching to maths and physics as a result of the weekend."
He has also used the researchers carefully in the school; he does not expose them to large groups. "It's quality time with the pupils that counts," he says. He notices that when they're with the pupils, much of the conversation is about science. The researchers are self-selected, but he sees several motivations behind their involvement.
"Some want to put something back into education, to show what can be achieved; others enjoy contributing their own bit of expertise to a project; and there are one or two CV fillers," he says.
He believes that the chief value of the PRI is that it focuses teachers' attention on how children think scientifically, and that the research briefs help pupils to "see the point of science". He thinks there has been a payoff at Westfield already.
The percentage of A to E grades in science subjects went up from 36 per cent to 45 per cent this year. For Denise Gault, the professionalism of the PRI is its strength. "The whole scheme has been followed through - not like some of these ad hoc initiatives which fizzle."
Part of the follow-through which the PRI offers are science fairs and regional conferences where students meet and describe their projects to each other. There's also the lively magazine Prism which charts the progress of the initiative and gives scientific credibility to the work the pupils have done.
For details about researchers in residence, school science fairs and conferences, Prism, and other aspects of the Pupil Researcher Initiative, contact the Centre for Science Education, Sheffield Hallam University, Collegiate Crescent Campus, Sheffield S10 2BP. Tel: 0114 253 2211. The PRI website is:http:www.shu.ac.ukschoolsscipri