Scientists agree more powerful spacecraft - and, ideally, rocks returned to Earth from Mars - are needed to prove whether tiny organisms like bacteria ever existed on the red planet.
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 serpentinisation.
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.
The Curiosity rover, launched in 2011 with about $2.5 billion worth of scientific equipment with the intent of exploring and analyzing Mars' Gale Crater. Over time, a picture of the ebb and flow of methane on Mars has emerged.
"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). Yet over the course of 55 Earth months (three Martian years), Webster and his team were able to use SAM to detect tiny, regular patterns in which methane-natural gas-increased from 0.24 to 0.65 parts per billion at the end of northern Mars' summer. "Both radiation and harsh chemicals break down organic matter", Eigenbrode continued.
The methane observations provide "one of the most compelling" cases for present-day life, she said.
"The only thing that fits the data is that you have a source of methane below the surface".
"With this new data, we again can not rule out microbial activity as a potential source", Webster said. "[But] it could also be rock chemistry".
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.
The new findings - "tough" organic molecules in three-billion-year-old sedimentary rocks near the surface, as well as seasonal variations in the levels of methane in the atmosphere - appear in the June 8 edition of the journal Science.
But the deposits were much smaller than they had anticipated. The key samples in the latest findings came from a spot 6.4 kilometres away.
Curiosity dug up samples at Mojave and Confidence Hills near Pahrump Hills.
"We have detected the bits and pieces of something bigger", said Eigenbrode.
"The detective work they did is worthy of Sherlock Holmes", said Katherine Freeman, a professor of geosciences at Pennsylvania State University who was not involved with the research.
"They could be changed from something like we've observed at the base of the mountain into methane that eventually makes its way back in to the atmosphere", she said. The livestream should kick off shortly before the press conference is scheduled to begin, and as with all NASA events it will be live streamed so we can all enjoy it from the comfort of our office desks.
"Ideally we want to get to samples that have not been irradiated". That could even be happening beneath the surface now, the researchers said. This is also when life was evolving on our own planet.