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Studying Mars -

Of all the planets in our solar system, Mars is one of the most studied. Its close proximity to Earth has made it an obvious choice for exploration over the past few decades.

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The Red Planet -

Even among non-experts, Mars is known for being covered in dust and for having a sort of rusty hue. Indeed, it is often referred to as the "Red Planet."

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Presence of rusted iron -

For years now, scientists have understood that the planet’s red color comes from rusted iron minerals in the dust that is found all over it.

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Hematite theory -

Previous analyses of the iron oxide on Mars led researchers to believe that it was a dry mineral called hematite. According to new research, however, that may incorrect.

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The question at hand -

For the avoidance of doubt, the fact that Mars is red is not being contested. Rather, the new study offers a different explanation for why the planet is that color.

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Iron oxide -

Iron oxide exists on Mars because, at some point, the iron within the planet’s rocks reacted with water or with water and oxygen in the air.

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Rust on Earth -

For those not familiar with the chemical processes that produce rust, this is largely the same process that forms rust here on Earth.

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Settling as dust -

Over billions of years, the iron oxide on Mars broke down into dust and settled across the planet.

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Transported by winds -

It was moved about by strong Martian winds, the likes of which still kick up dust storms on the planet today.

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Existing research -

Until this most recent study, the only analyses of the iron oxide on Mars were based solely on observations made by spacecraft.

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No water detected -

These analyses did not detect any evidence of water, which led researchers to believe the type of iron oxide present on Mars was hematite.

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Dry mineral -

Hematite is a dry mineral and a main component of iron ore. If the iron oxide on Mars is hematite, it most likely formed over the course of billions of years through interactions with the planet’s atmosphere.

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Timing -

Furthermore, it must have formed later in Mars’ history, after the planet is believed to have had lakes and rivers on its surface.

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2025 study -

According to a study published in February 2025 in Nature Communications, however, the iron oxide on Mars may actually be ferrihydrite.

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Ferrihydrite -

Ferrihydrite differs from hematite in the sense that it forms in the presence of cool water.

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Changing theories -

The discovery of this type of iron oxide on Mars may change scientists’ understanding of what the planet was like billions of years ago.

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Age-old question -

Scientists have long since wondered about the exact composition of the iron oxide found on Mars.

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Difficult to determine -

However, it has historically been very difficult to examine because the particles are absolutely tiny (we’re talking nanometers or less).

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Data from various devices -

The new study used data collected by various devices, including the European Space Agency’s Mars Express Orbiter and the ExoMars Trace Gas Orbiter.

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Results -

The results of various complex analyses suggest evidence of water-rich minerals on even the dustiest areas of Mars.

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Interpreting the results -

According to the study’s authors, this discovery offers some interesting clues about the planet’s geologic and climate history.

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More liquid water -

For example, the presence of water-containing rust over large parts of Mars’ surface suggests that it may have been home to more liquid water than previously thought.

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Scope of the study -

It is important to note that this recent study did not focus on exactly when Mars’ ferrihydrite reserves were formed.

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Estimates -

However, on the basis that the mineral forms in cool water, researchers believe that it may have formed around three billion years ago.

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Going back further -

This is as opposed to millions of years before, when the planet would have been warmer and wetter.

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Favorable conditions -

According to the study’s authors, around three billion years ago the conditions on Mars were favorable for the creation of ferrihydrite.

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Period of volcanic activity -

Indeed, this was a period of intense volcanic activity that likely triggered ice-melting events and interactions between water and rock.

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Period of transition -

Scientists therefore believe that the ferrihydrite formed during a period when Mars was transitioning from its earlier, wetter state to its current dry environment.

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In the Martian rock -

Researchers believe that in addition to being in the dust, ferrihydrite may also be present in the layers of Martian rock.

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Going forward -

There are plans to examine samples and hopefully broaden even further our understanding of the history of water, and therefore life, on Mars.

Sources: (CNN)

See also: Is there a mysterious ninth planet in our solar system?

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