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If there’s one thing that our closest neighbor in the solar system is well known for, it’s its color.
Thanks to the red shade its surface appears, we’ve long called Mars the Red Planet. But did you ever wonder why, in comparison to our own shades of blue, green, and desert yellow, Mars is of an entirely different hue?
Well thanks to researchers at Brown University and the University of Bern, we may be much closer to an answer.
NASA
Earth’s color palate is a result, of course, of the materials of the oceans and the land masses that we all live on. The oceans appear blue from space, since they reflect blue light, whilst the fields, forests and other areas of vegetation that cover much of our land comprise of plants, which reflect green light.
So we know that when we look at Mars – whether with our bare eyes, through a telescope, or from spacecraft or vessels like the International Space station – something entirely different must be going on on Mars’s surface.
Since Mars is the only other planet in our Solar System that is within the Goldilocks Zone – meaning that there’s a chance it could be capable of sustaining human life – its mysterious red surface is of immense interest to scientists across the world.
It’s no wonder that space agencies all around the world have been competing to collect data from Mars, with SpaceX even targeting manned flights there in the near future.
Through years of observation, scientists have arrived at various theories, including the most popular one that a mineral called hematite – which has a rusty brown color thanks to its high iron content – is responsible for the color we see when we look towards our planetary neighbor.
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However, according to the results of the fresh study – which was recently published in the journal Nature Communications – the reddish color is a result of the prevalence of another mineral entirely. Rather than dry hematite, the researchers suggest that a water-rich mineral (also with a heavy iron content) called ferrihydrite is more likely the causative factor, as Adomas Valantinas – a postdoctoral fellow at Brown University – explained in a statement:
“The fundamental question of why Mars is red has been thought of for hundreds if not thousands of years. From our analysis, we believe ferrihydrite is everywhere in the dust and also probably in the rock formations, as well. We’re not the first to consider ferrihydrite as the reason for why Mars is red, but it has never been proven the way we proved it now using observational data and novel laboratory methods to essentially make a Martian dust in the lab.”
To reach this conclusion, the research team worked through data obtained from various Mars missions, comparing previously obtained observations and measurements with their own lab-gathered data concerning the interaction of light with various iron-rich minerals under conditions that replicated those on Mars.
The findings when ferrihydrite was observed under these conditions, Valantinas notes, were very much akin to our observations of the Martian surface:
“Martian dust is very small in size, so to conduct realistic and accurate measurements we simulated the particle sizes of our mixtures to fit the ones on Mars. We used an advanced grinder machine, which reduced the size of our ferrihydrite and basalt to submicron sizes. The final size was 1/100th of a human hair, and the reflected light spectra of these mixtures provide a good match to the observations from orbit and red surface on Mars.”
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Why has ferrihydrite not been considered in the past? Well, mostly because what we know about Mars is that its surface is very dry, suggesting that a dry mineral like hematite would be present on the surface.
However, this does not take into account the billions of years of Martian history that we don’t know about. Since the study suggests that ferrihydrite – a mineral that forms in cool, wet conditions – could be covering the Red Planet’s surface, we might deduce that liquid water was once present on Mars:
“What we know from this study is the evidence points to ferrihydrite forming, and for that to happen there must have been conditions where oxygen, from air or other sources, and water could react with iron. Those conditions were very different from today’s dry, cold environment. As Martian winds spread this dust everywhere, it created the planet’s iconic red appearance.”
While the true nature of Mars’s surface won’t be fully confirmed until samples are returned in the future, this study gives new life to the theories that Mars may once have had a more complex atmosphere and could have even supported life on its surface.
All valuable information in the search for future habitable planets.
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