Mars may have been much different than previously thought

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Our red neighbor is said to have been a warm, humid paradise 3.5 billion years ago. But now a new study suggests that this assumption may be wrong.

Mars may have been much cooler in the distant past than many scientists think. This is the conclusion of a computer-aided comparison of some 10,000 river valleys on the Red Planet with eroded areas on Earth.

According to the a new study, the Martian riverbeds could have been formed by meltwater under thick glaciers just over 3.5 billion years ago, similar to the valleys on Devon Island in northern Canada, reports a team led by Anna Grau Galofre of the University of British Columbia in Nature Geoscience.

However, this new finding are at odds with the conventional assumption that Mars was a largely warm and humid world about 3.5 billion years ago, with rivers splashing under open skies. In fact, climate simulations have long suggested that such a view might be too simple: at that time, the sun gave off far less radiation than it does today, which has never really suited Mars as an ecological paradise.

Nevertheless, many researchers are sticking to the scenario of the humid, warm early mars, which, among other things, is linked to surprisingly large amounts of CO2 in the Martian atmosphere of the time. However, studies such as that of Grau Galofre once again cast doubt on this view. Mars could have been therefore more of an ice planet in its childhood, where volcanoes, meteorite impacts and fluctuating seasons caused some of the glaciers to melt. In this case, it would have been the outflows under the ice that gave the Martian surface its present form.

Warm and humid or cold and icy: Which of the scenarios is closer to the truth is likely to remain open with the current study. Especially since the results of the analysis are far from clear: Most likely, different geological processes were involved in the formation of the different river valleys, the geophysicists write in their paper. Thus, there may have been rivers and lakes in selected regions – while many other areas were probably covered by thick ice.