A recent international study, partially funded by NASA, sheds light on the origins of Mars’ distinctive red hue and supports the idea that the planet once had a cooler, wetter climate that may have been suitable for life. Today, Mars’ atmosphere is too frigid and sparse to allow liquid water to exist on its surface for extended periods. Nevertheless, numerous missions from NASA and other organizations have uncovered signs that water was plentiful on Mars billions of years ago, evidenced by features resembling ancient riverbeds and lakes, as well as minerals that only develop in the presence of liquid water.

The study, published in the journal Nature Communications, proposes that ferrihydrite, a water-rich iron mineral, could be primarily responsible for Mars’ reddish dust. While Martian dust consists of a variety of minerals, including iron oxides, this research indicates that ferrihydrite is a key contributor to the planet’s coloration.

This discovery provides intriguing insights into Mars’ wetter and potentially habitable history since ferrihydrite forms in cooler water conditions and at lower temperatures than other minerals previously thought to explain the planet’s color, such as hematite. This implies that Mars might have had an environment conducive to liquid water before it underwent a transition from wet to dry conditions billions of years ago.

The researchers utilized data from various Mars missions, integrating orbital observations from NASA’s Mars Reconnaissance Orbiter and ESA’s Mars Express and Trace Gas Orbiter with ground-level data collected by NASA rovers like Curiosity, Sojourner, and Opportunity. The instruments aboard these orbiters and rovers provided detailed spectral information about the Martian surface’s dusty composition. These findings were then compared with laboratory experiments designed to simulate Martian conditions and examine how light interacts with ferrihydrite particles and other minerals. The validity of the proposed formation model could be conclusively tested once samples from Mars are returned to Earth for further analysis.

Source: NASA