A Scottish-led team of scientists has revealed a pointer to the possibility of life on Mars. They've extracted methane gas from Martian rock and say it could be a source of food for life on the red planet.
Is there life on Mars? It's not for want of asking. David Bowie for one has been singing about it for years.
If there is, the chances of it being in the form of little green persons are vanishingly small. It's more likely to resemble the sort of organisms that prove so hard to shift from our shower curtains: microscopic but persistent.
So why does Martian methane matter? It could be the chemical marker that tells us that life is there, the gas given out by living things below the planet's surface.
So far the evidence has been inconclusive. Plumes of methane have been detected in Mars's atmosphere, but that is not proof enough. Even though Mars is not volcanic, other geological processes could be at work.
This project took another tack.
It wanted to examine whether methane could exist in the Martian rocks as a food source for life. That's none too appetising for us but there are life forms here on Earth which consume methane.
The research was led by Aberdeen University in collaboration with the Scottish Universities Environmental Research Centre, Glasgow University and two Canadian institutions: Brock University and the University of Western Ontario.
They took meteorites known to have come to Earth from Mars and crushed them. These meteorites were precious as the total number of known Martian meteorites is small.
But the results were worth it. Six - all containing volcanic rock - contained methane.
Professor John Parnell, of Aberdeen's School of Geosciences, says the research provides a strong indication that rocks on Mars contain a large reservoir of methane.
"This is significant because if simple life did exist below the surface, then it could use methane as a food source, in much the same way as microbes do in a range of environments on earth," he said.
"So while we cannot say that this discovery is proof of the existence of life on Mars, it gives strong encouragement to continue looking for methane sources that could support life."
Professor Nigel Blamey, of Brock University, said: "Measurements we made on samples from earth over many years gave us confidence that we could get this important data from tiny pieces of these precious meteorites from Mars.
"The method we use can detect extremely small quantities of gases like methane, and we plan to expand upon our research by analysing more meteorites in the future."
The findings, published in Nature Communications, suggest something even more intriguing: that the conditions for life could also exist on other rocky planets beyond our own solar system.
Professor Parnell said: "Methane is a starting point for complex organic molecules.
"Our work implies that on many other rocky volcanic planets, in our galaxy and others, there may be methane, which could contribute to the building blocks of life."