Mars has been known as the Red Planet for thousands of years; even the ancient Egyptians called it ‘The Red One’ (Her Desher).
Now scientists think they have worked out exactly what gives our closest planetary neighbour its rusty hue, and they’ve even made a copy of the Martian dust in a lab.
A study published in Nature today says that the iron oxide could be a different mineral to the one most commonly presumed.
Researchers said the water-rich iron mineral ferrihydrite could be the main culprit, as opposed to hematite, which is formed in drier conditions.
Adomas Valantinas of the Universit of Bern said that while the idea has been suggested before, this is the first time that such dust was recreated, and the idea ‘proven’ using observations.
The only way to 100% prove the theory is by looking at samples, which won’t happen for a while.
Nasa’s Perseverance Rover has been collecting soil and rock from the planet so they can be brought back to Earth by a future mission. If and when this happens, we will know for sure.
Mr Valantinas said: ‘The fundamental question of why Mars is red has been thought of for hundreds if not for 1000s 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 test their theory, they tried to recreate the dust by grinding particles to just one hundredth of the width of a human hair, given that on Mars it is very small in size.
This meant they could compare how it reflected light with the planet itself, to see if it was a match with observations.
If the theory is correct, it won’t only solve the mystery of the colour.
It would also give clues about the environment of Mars back in the day, because ferrihydrite forms when there is cool water.
There’s none of that on Mars now, but potentially there might have been billions of years ago, meaning the past might potentially have been more habitable.
Mr Valantinas added: ‘Was there ever life? To understand that, you need to understand the conditions that were present during the time of this mineral formation.’
For ferrihydrite to form, they must have been conditions where oxygen, from air or other sources, and water could react with iron to create the oxide.
‘Those conditions were very different from today’s dry, cold environment,’ he said. ‘As Martian winds spread this dust everywhere, it created the planet’s iconic red appearance.’
Humans could be headed to the Red Planet soon if Elon Musk gets his way, some of them on a one-way trip to start a colony.
So the more we know about it, the better – especially if we find out it may not have always been so inhospitable.
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