Mars’ surface, including the once-occupied Jezero Crater, has a history of liquid water, including lakes that have long since dried up. It was believed that the ancient water, carrying debris, was the sole reason behind the formation of channels that spread across Mars. The discovery that dry ice could also accomplish this has led to the reemergence of the question, “Is there water on Mars?”

Is there water on Mars?

Previously, scientists believed that there were only liquid water channels on Mars, just like on Earth. What was overlooked, however, was sublimation, the direct transition of a substance from solid to gas. Sublimation explains how CO2 ice disappears.

Frozen carbon dioxide, or dry ice, is found all over Mars, including in valleys. When CO2 ice sublimates in one of these channels, the resulting gas can push the debris further down the slope and continue to shape it.

A team of scientists led by Lonneke Roelofs from Utrecht University in the Netherlands found that the sublimation of CO2 ice could have shaped the pits on Mars. This discovery raises the question: “Is there still water on Mars?” Or, was there water before but not anymore?

This finding may mean that the last occurrence of liquid water on Mars could be much older than previously thought. It could also imply that the window for life to emerge and evolve on Mars is likely smaller.

Roelofs and colleagues stated in a recent publication in Communications Earth & Environment, “Under the atmospheric conditions of Mars, the sublimation of CO2 ice could fluidize the sediment and create morphologies similar to those observed on Mars.”

Are the causes of channels on Earth and Mars different? Channels on Earth and Mars have fundamentally similar morphologies. The difference lies in knowing that the formation of these channels on Earth involves and relies on liquid water. Such activities include the opening of new channels and the transport of more debris downstream.

While there was once enough stable liquid water on ancient Mars to accomplish this, there is not enough liquid on the planet’s current surface to sustain such activity. This is where sublimation comes into play. Coinciding with the material starting to flow, CO2 ice has been observed on the surface of Mars.

This experiment, showing that channels and similar systems can be shaped not only by liquid water but also by sublimation, raises questions about how long a sufficient source of liquid water has been available for any organisms (if they exist) to survive on Mars.

The habitability period may be shorter than once thought. Does this mean nothing lives on Mars? Not necessarily, but the findings of Roelofs and her team may influence how we view the habitability of the planet in the future.

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