Iron mineral reason for Mars' red colour, study suggests; hints planet was once habitable

New Delhi: The red color of Mars could be due to the presence of an iron-containing mineral, which requires cool water to form, suggesting that the planet may have been habitable in the past, according to a new study.

Dust on the Red Planet is known to be a mixture of various minerals, including iron oxides, one of which -- ferrihydrite -- could be the reason for the planet's color, the study published in the journal Nature Communications suggested.

"We’re not the first to consider ferrihydrite as the reason for why Mars is red, but we can now better test this using observational data and novel laboratory methods to essentially make Martian dust in the lab," said lead author Adam Valantinas, a postdoctoral fellow at Brown University, US.

"From our analysis, we believe ferrihydrite is everywhere in the dust and also probably in the rock formations as well," Valantinas added.

However, because ferrihydrite forms in the presence of cool water and at lower temperatures than minerals previously thought to render the red color, such as hematite, the findings suggest that Mars may have had an environment capable of sustaining liquid water.

Mars's environment is believed to have transitioned from wet to dry billions of years ago when its atmosphere was stripped away by solar winds. The planet had a weak magnetic field (due to a cooling core), which failed to protect it from the solar winds, leaving Mars dry and cold.

The study analysed data gathered from multiple missions to Mars conducted by space agencies, including NASA and the European Space Agency. The team then compared the results with those from lab experiments, where they tested how light interacts with ferrihydrite particles and other minerals under simulated Martian conditions.

Analysis of samples from Mars, currently being collected by NASA’s Perseverance rover, will reveal whether the team’s findings -- proposed as a theory for Mars's formation -- are definitively correct. The rover was launched in July 2020 and landed on Mars in February 2021.

The researchers aim to understand Mars’s ancient climate and its chemical processes to better determine if the planet was once habitable.

"To understand that, you need to understand the conditions that were present during the time of this mineral’s formation. Those conditions were very different from today's dry, cold environment," Valantinas said.

"What we know from this study is that the evidence points to ferrihydrite forming, and for that to happen, there must have been conditions where oxygen from the air or other sources and water could react with iron," the lead author explained.