The Secret of the Red Planet - Spectacular Research Reveals Why Mars is Red

Mars is famous for its iconic red color and is therefore also called the “ Red Planet .” A new study could now revolutionize the previous explanation for this coloring. The new study was published in the journal “ Nature Communications .”

Until now, researchers have assumed that the color comes from rusted iron minerals in the dust that covers the planet. At some point, the iron in the rocks of Mars reacted with water, or water and atmospheric oxygen, to form iron oxide - similar to how rust forms on Earth, or so the previous assumption was.

Over billions of years, the iron oxide crumbled into dust and settled on the planet after being moved by Martian winds that still stir up massive dust storms.

Previous analyses of iron oxide on Mars, however, initially showed no evidence of water, which led researchers to assume that the iron oxide must be hematite. The dry mineral, a main component of iron ore, was formed by reactions with the Martian atmosphere in a process that lasted for billions of years.

Now, however, researchers have found evidence that the red color could be caused by a water-containing mineral called ferrihydrite, which forms quickly in cool water - and probably formed on Mars when there was still water on the surface, before the planet became colder and more inhospitable.

If researchers can figure out how the iron oxide in Martian dust evolved, they could essentially look back in time. This would provide exciting insights into what the environment and climate on ancient Mars were like.

But even though the dust covers everything on Mars, it is difficult to study and presents a mystery, said Briony Horgan, a professor of planetary sciences at Purdue University in West Lafayette, Indiana.

"The particles (of oxidized iron) are so small (nanometers or less) that they do not have a truly defined crystal structure and cannot be called true minerals," said Horgan.

A special color camera on Mars missions revealed the exact size and composition of the dust particles and enabled researchers to create their own version on Earth.

This dust could then be examined with X-ray machines and compared with the spacecraft's data. "We found that ferrihydrite mixed with basalt, a volcanic rock, best matches the minerals seen by spacecraft on Mars," said Valantinas, who began his research at the University of Bern with data from the Trace Gas Orbiter.

"The most important conclusion is that ferrihydrite could only form when water was still present on the surface , and that Mars rusted earlier than we previously thought. This suggests that Mars once had an environment in which liquid water was present, which is an essential prerequisite for life."

The study shows that for ferrihydrite to form on Mars, both oxygen - whether from the atmosphere or other sources - and water that can react with iron had to be present.

"Once we have these precious samples in the lab, we will be able to measure exactly what this means for our understanding of the history of water - and the possibility of life - on Mars," said Colin Wilson, scientist for the Trace Gas Orbiter and Mars Express project, in a statement

The mystery of water on Mars has occupied many researchers: Only recently were evidences of ancient "wave ripples" discovered on the surface of Mars. According to Claire Mondro of the California Institute of Technology, these structures, which indicate liquid water about 3.7 billion years ago, could only have formed under water that was exposed to the atmosphere and influenced by the wind.

Claire Mondro emphasizes that the presence of liquid water expands the possibilities for microbial life in the history of Mars.

However, an independent review in September 2023 estimated the cost at up to $10.9 billion and pushed the timeframe back to 2040. Both new options use a radioisotope thermoelectric generator (RTG) instead of solar cells to make the spacecraft independent of sunlight.