Why is Mars red? This news study reveals the role of a rust-coloured dust

The red colour of Mars has long fascinated scientists. Now, a recent study published in the peer-reviewed British journal Nature Communications offers an explanation for the planet’s reddish hue.

Adomas Valantinas, a researcher from Brown University and lead author of the study, said the question of why Mars is red has been existing for centuries. He says now the understanding of Mars’ colour has significantly improved after this study.

The new explanation, which identifies the rust-coloured dust called ferrihydrite as the cause for the red colour, also sheds light on the planet’s history of water and its potential to support life.

Mars’ red colour explained

Since Mars no longer has liquid water, scientists initially thought its rust red colour came from dry iron oxides like hematite in the dust. But new analysis of spacecraft data and laboratory techniques suggests that the planet's red hue is better explained by ferrihydrite — an iron oxide that forms in the presence of water.

Ferrihydrite forms rapidly in cold water, indicating that it likely developed on early Mars when the planet still had liquid water.

While some researchers had earlier suggested that ferrihydrite was the cause of Mars' red colour, definitive proof had been lacking.

Using observational data and advanced laboratory methods to create Martian dust analogues, the researchers have now provided strong evidence for this theory.

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Potential for life on Mars

The discovery that ferrihydrite is a key component of Martian dust could have significant implications for understanding Mars' history and the possibility of past life. Unlike hematite, which forms in warm or dry conditions, ferrihydrite develops in cooler, water-rich environments.

Valantinas explains that the presence of ferrihydrite on Mars suggests the planet once had an environment with liquid water, a crucial requirement for life.

The study indicates that ferrihydrite formation required both oxygen — possibly from the atmosphere or other sources — and water capable of reacting with iron, hinting at conditions quite different from today’s dry, cold Mars.

Promising results

Study co-author Jack Mustard described the research as a "door-opening opportunity," emphasising that while the findings are promising, they can only be fully confirmed with physical samples from Mars. These are currently being collected by NASA's Perseverance rover, and once returned to Earth, they will allow scientists to verify whether the ferrihydrite theory is correct.

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FAQs

1. What is Ferrihydrite?
Ferrihydrite is a type of iron oxide mineral that forms in the presence of water. It usually develops in cool, wet conditions and is often found as a fine, rusty-coloured dust.


2. What is the weather on Mars now?
Mars is now extremely cold and dry, with most of its water trapped as ice at the poles or in underground reserves.