Why is Mars red? Scientists think they've discovered why

Are we alone in the universe? New research could offer some clues after scientists created a replica of the dust found on Mars.

Researchers combined European Space Agency (ESA) and NASA spacecraft data with cutting edge laboratory experiments. The results could help explain how Mars evolved over billions of years.

Mars is known as the Red Planet but new data suggests there's a better name - the Rusty Planet. 

The scientists' analysis showed that Mars' red colour is similar to iron oxides containing water, known as ferrihydrite. Ferrihydrite typically forms quickly in the presence of cool water, so must have formed when Mars still had water on its surface. 

The ferrihydrite has kept its watery signature to the present day, despite being ground down and spread around the planet since its formation.

According to lead author Adomas Valantinas, from Brown University: "We were trying to create a replica martian dust in the laboratory using different types of iron oxide. We found that ferrihydrite mixed with basalt, a volcanic rock, best fits the minerals seen by spacecraft at Mars."

Previous studies have also suggested ferrihydrite might be present in martian dust, but Valantinas' team have provided what they say is the first comprehensive proof.

The replica martian dust was created using an advanced grinder machine to create the realistic dust with a grain size equivalent to one-hundredth of a human hair. They then analyzed their samples using the same techniques as orbiting spacecraft in order to make a direct comparison, finally identifying ferrihydrite as the best match. 

"This study is the result of the complementary datasets from the fleet of international missions exploring Mars from orbit and at ground level," explained Colin Wilson, from ESA.

Analysis of the dust's mineralogy helped show that even highly dusty regions of the planet contain water-rich minerals. 

Life on Mars?

The presence of water suggests Mars may have supported life at some stage. But scientists have never been sure if the rust was created by water on the surface, or by moisture in the atmosphere.

By recreating the dust in a laboratory, their experiment suggests the water was on the surface, meaning that Mars became red, or rusty, earlier than scientists thought. It also reinforces the belief that there was water on Mars - and again raises the question: did something live on the 'rusty planet'?

China and the U.S. are planning separate missions to collect samples from Mars and fly them back to Earth. Those missions could be several years away Meanwhile, tech billionaire Elon Musk has suggested humans could eventually live on Mars.

So, this research may focus on the planet's past but it could also have implications for its future.

Chinese research

In separate research, ground-penetrating radar data obtained by China's Zhurong rover has revealed buried beneath the Martian surface evidence of what look like sandy beaches from the shoreline of a large ocean that may have existed long ago on the planet's northern plains.

The findings are the latest evidence indicating the existence of this hypothesized ocean, called Deuteronilus, roughly 3.5 to 4 billion years ago, a time when Mars - now cold and desolate - possessed a thicker atmosphere and warmer climate. An ocean of liquid water on the Martian surface, according to scientists, potentially could have harbored living organisms, much like the primordial seas of early Earth.

The rover, which operated from May 2021 to May 2022, journeyed about 1.2 miles (1.9 km) in an area that exhibits surface features suggestive of an ancient shoreline. Its ground-penetrating radar, which transmitted high-frequency radio waves into the ground that reflected off subsurface features, probed up to 80 meters (260 feet) beneath the surface.

"The Martian surface has changed dramatically over 3.5 billion years, but by using ground-penetrating radar we found direct evidence of coastal deposits that weren't visible from the surface," said Guangzhou University planetary scientist Hai Liu, a member of the science team for China's Tianwen-1 mission that included the rover.

On Earth, beach deposits of this size would have needed millions of years to form, the researchers said, suggesting that on Mars there was a large and long-lived body of water with wave action that distributed sediments carried into it by rivers flowing from nearby highlands.

The rover explored in the southern part of Utopia Planitia, a large plain in the Martian northern hemisphere.

Earth, Mars and the solar system's other planets formed roughly 4.5 billion years ago. That means Deuteronilus would have disappeared approximately a billion years into Martian history, when the planet's climate changed dramatically.