Washington: The Red Planet has been under constant monitoring by numerous space agencies, in order to prepare for future missions to Mars.
In the course of the years that Curiosity and Opportunity – rovers sent to Mars by NASA – have been scaling the rocky terrains of the planet, we have been treated to numerous images and discoveries found on the Martian surface, most of them being ground-breaking.
Now, a team of researchers, including Ravi Kumar Kopparapu, an Indian-origin scientist, from University of Maryland in the US, have found that liquid water, triggered by a build-up of greenhouse gases that gave rise to dramatic climate cycles on early Mars, have carved out deep canyons and extensive valley networks on the red planet's surface.
Scientists have long debated how these canyons and valley networks - like the kinds carved by running water over millions of years on Earth - could form on Mars some 3.8 billion years ago, a time many believe the planet was frozen.
The researchers suggest that a glacier-covered early Mars may have experienced long warm periods, lasting up to 10 million years at a time, caused by a thick atmosphere of carbon dioxide and hydrogen.
The team found the warming cycles would have lasted long enough, and produced enough water, to create the features.
"With the cycling hypothesis, you get these long periods of warmth that give you sufficient time to form all the different Martian valley networks," said Natasha Batalha, graduate student at Pennsylvania State University in the US.
Previous research suggested that asteroid impacts warmed the planet, creating steam atmospheres that led to rain.
However, those warm periods would have much shorter durations and struggled to produce enough water.
"We think Mars had to be warm for millions to tens of millions of years, and the impact hypothesis can keep it warm for thousands of years," said Jim Kasting, Professor at Penn State.
Kasting said valleys on the Martian surface are similar in width to the Colorado River Canyon.
Scientists estimate it took 16 million years for the Colorado River, swollen seasonally as the snow melts in the Rocky Mountains, to carve the nearby Grand Canyon.
Using climate models, the team showed warming periods - caused when greenhouse gases reached a certain tipping point - lasted millions of years on Mars.
With the right choice of parameters, these warm periods can last up to 10 million years.
According to researchers, greenhouse gases accumulated in the atmosphere gradually, belched by volcanic eruptions, released by cooling magma on the surface or seeping up from the planet's crust.
(With PTI inputs)