Did you know Mars once had rivers, streams and lakes?

Around 3.6 to 3.0 billion years ago, Mars' climate was at least occasionally warm enough for rivers and lakes. It was inferred to have been habitable. However, the surface today is a cold desert. Scientists are exploring whether or not Mars can support life. They are trying to find out answers that can help them probe the potential of human settlement on the Red Planet, and what it might look like. In an attempt to investigate something that seems quite unrealistic, scientists have taken up several spacecraft missions related to the planet Mars, such as orbiters and rovers. From Mariner 4 (1964) to Mars 2020 (2020), missions to Mars have unfolded several mysteries and produced remarkable findings. 

Mars is the prime focus for scientists when it comes to living outside Earth. But why is it so? Scientists have noted that Mars once had rivers as there are tracks of rivers, streams and lakes, which apparently dried up about three billion years ago. 

A new study, published on May 25 in Science Advances, probes the changing spatial distribution of water flow on Mars. It has been revealed that the change charts major changes in Mars' greenhouse effect. 

The study noted that the analysis of the greenhouse effect within the ensemble of global climate model simulations suggests that this shift was "primarily driven by waning non-CO2 radiative forcing, and not changes in CO2 radiative forcing". 

The findings highlight that the loss was triggered by a layer of thin, icy clouds high in the atmosphere of Mars. It trapped heat and warmed the planet, acting like translucent greenhouse glass. 

Edwin Kite, who is a geophysical scientist at the University of Chicago, said, "People have put forward different ideas, but we're not sure what caused the climate to change so dramatically. We'd really like to understand, especially because it's the only planet we definitely know changed from habitable to uninhabitable." 

Kite is the first author of a new study done with collaborations with Bowen Fan, who is a graduate student at the University of Chicago student, scientists from the Smithsonian Institution, Planetary Science Institute, California Institute of Technology Jet Propulsion Laboratory, and Aeolis Research. 

For the study, scientists have analysed maps based on thousands of pictures of Mars taken from orbit by satellites to create a timeline of how river activity changed in elevation and latitude. After that, they could combine that with simulations of different climate conditions. 

The study noted that the "past climate on Mars can be probed using the spatial distribution of climate-sensitive landforms." 

"We analyzed global databases of water-worked landforms and identified changes in the spatial distribution of rivers over time. These changes are simply explained by comparison to a simplified meltwater model driven by an ensemble of global climate model simulations," the study read.