The research, by a team led by geophysicist Edwin Kite from the University of Chicago in the US, provides a plausible explanation for an apparent data inconsistency that has puzzled scientists for a while.
Information compiled about ground layers on Mars – including that gathered by the rover Curiosity – indicate that fewer that three million years ago the planet had lakes full of liquid water. This has been perplexing, because other data, including the lack of weathering around the lake outflows, indicate that long before then most of the planet had become cold and dry.
For the lakes to form, therefore, there had to be a period of climate warming strong enough to induce ice to melt in sufficient quantities to form the gigantic lakes – and long enough to allow the lakes to endure for thousands of years, as sediment evidence suggests they did.
Kite and his colleagues used a numerical analysis to try to account for the apparent inconsistency, and posit one scenario that would explain it.
They suggest that shifts in the planet’s axis destabilised ice sheets, causing them to shrink and shift. Methane stored in the Martian soil and trapped beneath the ice was thus liberated and released into the atmosphere.
This, in turn, had a warming effect, melting ice and creating the lakes.
The researchers note that this proposed mechanism is “inconsistent with many previously proposed triggers for lake-forming climates” but fits well what they term a “methane-burst scenario”.
In an accompanying editorial, Alberto Fairen of the Centro de Astrobiología in Madrid, Spain, says that while it is unlikely that any single mechanism is sufficient to explain the existence of Martian lakes during otherwise arid periods, the methane-burst scenario nevertheless provides a fresh means by which to approach the evidence.