For years, NASA's Curiosity rover has patiently gathered samples on the surface of Mars. Today, scientists are announcing they've discovered conclusive evidence that several organic compounds are indeed found on the Red Planet.

On top of that, after keeping close tabs on methane levels in the Martian atmosphere, scientists have finally confirmed something weird is definitely going on, and they think they know what's causing it.

"Both these findings are breakthroughs in astrobiology," writes Utrecht University geoscientist Inge Loes ten Kate in this week's issue of Science.

"The results convincingly show the long-awaited detection of organic compounds on Mars."

A set of geological results recently delivered courtesy of Curiosity's drill bit provides a deeper understanding of the organic chemistry of the 300-million-year-old mudstone in two separate parts of Gale crater.

The samples were found to contain thiophene, 2- and 3-methylthiophenes, methanethiol, and dimethylsulfide.

These chemicals might not mean a great deal to most of us, but to areologists (that's Martian geologists) it's an indication that the organic chemistry in Martian mudstone is extremely similar to our own.

The super exciting part is that the method used to detect these chemicals indicates they're not floating around in the rock all alone, but are smaller pieces of organic chemistry that's been torn off even bigger, more complicated materials.

"With these new findings, Mars is telling us to stay the course and keep searching for evidence of life," said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters, in Washington.

"I'm confident that our ongoing and planned missions will unlock even more breathtaking discoveries on the Red Planet."

The other set of results announced today deals with the mysterious case of Mars's methane. Spikes of methane (CH4) were first noticed in the Red Planet's atmosphere several years ago, drawing intense debate over the hydrocarbon's possible source.

Data from the plucky rover Curiosity and the Trace Gas Orbiter high above the planet have spotted it in puffs, suggesting a dynamic process is churning it out parts per billion.

It should take methane several hundred years to break apart in the presence of UV light, but that's not what happened on Mars. The surge in methane seems to fade as quickly as it appears, indicating there's not just a variable source, but a methane sink as well.

A new analysis of data gathered by Curiosity has confirmed a long-term pattern of methane highs and lows, varying between 0.24 to 0.65 parts per billion.

The most exciting news is that the changes definitely match the Martian seasons, hitting a peak at the end of summer in the northern hemisphere.

"This is the first time we've seen something repeatable in the methane story, so it offers us a handle in understanding it," said lead author of the second paper Chris Webster of NASA's Jet Propulsion Laboratory (JPL).

"This is all possible because of Curiosity's longevity. The long duration has allowed us to see the patterns in this seasonal 'breathing.'" 

Here on Earth, 95 percent of all methane molecules are the product of living chemistry. That's not to say there are no non-biological sources, but on our world they're swamped by cow farts and belching bacteria.

But as tempting as it is to suggest Martian microbes are the source, for now there are plenty of other candidates to rule out first.

Leading contenders have included some sort of chemical reaction based on a rock called olivine, meteorites dropping organic materials into the atmosphere, or a release from a sub-surface reservoir close to the surface.

These might explain the increase in molecules, but they do still leave its rapid vanishing act wanting of an explanation.

NASA's Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft effectively ruled out cosmic origins following its analysis of the dust left after a close encounter with the comet Siding Spring in 2014.

A thick strata of olivine might be a potential contributor, leaking a steady flow of methane as it reacts with water and carbon dioxide in a process called serpentinisationThe timing of the pulses provides an important clue.

"The seasonal methane peaks in the summer of the Martian northern hemisphere so the source has to be affected by those increasing temperatures from greater sunlight," astrophysicist Alan Duffy from Swinburne University in Australia told ScienceAlert.

A crystalline water structure called a clathrate provides a perfect explanation.

"These clathrates lock the methane inside a water-ice crystal structure and are incredibly stable for millions of years until environmental conditions change and suddenly they can release that gas," says Duffy.

Previous research has suggested the temperatures required could be found at the poles in their respective winter seasons.

Inclusion of carbon dioxide in the mix could potentially lower the pressures required to form these lattices, allowing methane clathrates to form just a few metres below the surface.

Clathrates mightn't explain the origins of the methane molecules themselves, but their involvement would go a long way in explaining annual shifts in methane concentration.

As winter falls, gases are once again trapped in ice cages, helping explain at least some of the vanishing methane.

So, just where did the methane come from in the first place? Serpentinisation is still on the table, as are minute traces delivered by asteroids, and other chemical processes.

Some sort of biology can't be ruled out, of course, but any kind of complex organic chemistry would still tell us something about how life arose on Earth.

At this point, there's simply no way of knowing whether the organic molecules and the methane findings point to potential life on Mars.

Future testing of the carbon isotopes in the methane could make the picture clearer, but for now we can't get too carried away - although the new results are a massive step towards discovering even more.

"Are there signs of life on Mars?" said Michael Meyer, lead scientist for NASA's Mars Exploration Program, at NASA Headquarters.

"We don't know, but these results tell us we are on the right track."'

One thing is for sure, though - whatever we can figure out about the chemistry of Mars, it's almost certainly going to add precious details to our understanding of life in the cosmos.

The findings have been published in Science here and here.