A team of British-led scientists believes 20km-wide lakes of melted ice were dotted around parts of the planet’s equator three billion years ago, a period termed the Hesperian Epoch.
No one had expected to find evidence of a warm, wet climate capable of sustaining surface water on Mars during this period.
Lakes, seas and rivers may have existed on the planet between 3.8 billion and four billion years ago, experts believe. But before the Hesperian Epoch, the planet was assumed to have lost most of its atmosphere and turned cold and dry.
The researchers, including scientists from University College London, examined several flat-floored depressions located above Ares Vallis, a giant gorge that runs for 2,000 kilometres across the Martian equator.
The study revealed that small sinuous channels connected the depressions.
Their appearance suggests they were created by lakes on higher ground bursting their banks and water draining into lower-lying lakes.
Similar interconnected lakes created by melting permafrost can be found on Earth in the “thermokast” landscapes of Siberia and Alaska.