Why is Mars red? Scientists are looking for new clues that could provide an unexpected answer

For centuries, Mars has captivated scientists and the general public alike, especially for its characteristic reddish hue that has earned it the nickname 'red planet'. Now, after extensive research, experts may have the explanation for this phenomenon: rust, which results from the reaction of a compound with water and oxygen. This discovery not only arouses curiosity but also provides new clues about the possibility that the planet was habitable in the past.

Historically, it was suggested that Mars' reddish color was due to hematite, a dry, rust-like mineral. This theory suggested that the reaction occurred without the presence of moisture, a crucial detail in determining whether Mars could have been habitable.

However, space missions sent to Mars in recent decades have provided crucial data that have led researchers to reconsider these theories. The new hypothesis suggests that a water-rich iron mineral called ferrihydrite could be primarily responsible for the reddish dust that covers the planet.

Ferrihydrite is an iron oxide mineral that forms in water-rich environments and is commonly associated with the weathering of volcanic rocks and ash on Earth. The relevance of this mineral on the Martian surface had not been fully understood until now. According to the latest studies, this could be an essential component of Martian dust.

To reach these conclusions, the team of researchers analyzed data collected from several missions to Mars, including orbital observations made by NASA's Mars Reconnaissance Orbiter and the European Space Agency's Mars Express and Trace Gas Orbiters. Surface measurements from rovers such as Curiosity, Pathfinder and Opportunity were also taken into account. The results of this research were published on Tuesday in the journal Nature Communications.

The discovery is significant because it suggests that Mars' past may have been wetter and potentially habitable. Unlike hematite, which forms in warmer, drier conditions, ferrihydrite develops in the presence of cold water. This context offers new insights into a Mars that may have had an environment capable of sustaining liquid water, an essential element for life.

Did life exist on Mars? Although it cannot be confirmed yet, understanding the conditions under which ferrihydrite formed is key. "What we know from this study is that the evidence points to the formation of ferrihydrite, and for this to happen, there must have been an environment where oxygen, from the air or other sources, and water could react with iron," explains Adomas Valantinas, astronomer and co-author of the study. These conditions contrast drastically with the dry and cold environment that currently characterizes the planet.

Although research is ongoing, this study offers evidence that Mars once had favorable conditions for habitability. "This research is an opportunity to open new doors," says John Mustard, another researcher involved in the study. With each discovery, scientists come a little closer to understanding the mysteries of the red planet.

*This content was rewritten with the assistance of artificial intelligence, based on information from O Globo (GDA), and was reviewed by a journalist and an editor.