Why is Mars red: New insights into the planet’s distinctive color
A new study published in Nature Communications could reshape our understanding of Mars' climate history, Kazinform News Agency correspondent reports.
What did scientists discover?
Until now, Mars’ distinctive red color was believed to result from anhydrous hematite, formed through relatively recent weathering processes. However, an international team of researchers has found that the primary iron-containing mineral in Martian dust is ferrihydrite—a hydrated iron oxide (Fe₅O₈H · nH₂O).
This discovery suggests that the Red Planet experienced cold but wet periods in the past, calling into question previous models of its climatic evolution.
To confirm their findings, scientists conducted spectral comparisons between Martian dust and laboratory samples of ferrihydrite, basalt, and sulfates. The results showed that ferrihydrite best matched observational data. Additionally, laboratory experiments demonstrated its stability under present-day Martian conditions, indicating that this mineral has likely persisted on the planet’s surface for geological timescales due to the cold and arid environment.
Ferrihydrite provides a strong spectral match to Mars' red color, as its optical properties align more closely with spectral observations than those of hematite. Unlike hematite, ferrihydrite forms fine, poorly crystalline structures that interact with light in a way that explains the planet’s characteristic appearance.
What does this mean for Mars' history?
The presence of ferrihydrite indicates that Mars underwent aqueous alteration under cold and oxidizing conditions in the past. This process likely took place during the late Hesperian period, a time when the planet was transitioning from a wetter environment to its current hyper-arid climate.
Moreover, the discovery of ferrihydrite challenges the hypothesis that iron in Martian dust formed solely through prolonged dry oxidation. Instead, the findings suggest that Mars experienced episodic periods of moisture, during which active chemical transformation of rocks occurred.
How will this impact future research?
This discovery is significant not only for understanding Mars' history but also for the search for signs of life. Ferrihydrite often forms in cold, aqueous environments, suggesting that ancient Mars may have had conditions suitable for life.
Future missions, such as the Mars Sample Return program, will be able to analyze Martian dust in greater detail and confirm the presence of ferrihydrite in samples brought back to Earth. This will help scientists determine the exact mechanism of its formation and provide more precise insights into the Red Planet’s climatic past.
Earlier, Kazinform News Agency reported on crucial insights into the evolution of the ancient Martian environment" at Utopia Planitia.
