Scientists have made a surprising discovery regarding the color of Mars. Sign up for CNN’s Wonder Theory science newsletter to stay updated on the latest scientific breakthroughs. Mars, known for its distinctive rusty hue, has been commonly referred to as the red planet. However, a recent finding by scientists challenges the existing theory behind the planet’s color.
Mars is among the most extensively studied planets in our solar system, thanks to its close proximity to Earth and the numerous spacecraft missions that have explored its surface over the years. Data collected from orbiters and landers indicate that the red color of Mars is a result of iron minerals that have oxidized over time, forming iron oxide within the dust that blankets the planet.
Previous research had suggested that the iron oxide on Mars was likely hematite, a dry mineral believed to have formed through interactions with the Martian atmosphere over billions of years. However, a new study combining data from various missions and laboratory experiments with Martian dust proposes that a mineral called ferrihydrite, which forms in the presence of water, may be responsible for Mars’ red hue. This finding could potentially alter our understanding of Mars’ ancient environment and whether it was once capable of supporting life.
Lead study author Adomas Valantinas of Brown University explained, “Mars is still the Red Planet, but our understanding of its coloration has evolved.” Scientists are intrigued by the composition of the iron oxide in Martian dust, as it could offer insights into the planet’s past climate and environment. While researching Martian dust presents challenges due to its small particle size and lack of defined crystal structure, the new analysis points to ferrihydrite as a key component in Mars’ reddish coloring.
The formation of the red component in Mars dust is believed to be linked to the presence of ferrihydrite, a poorly crystalline iron oxide. Previous research suggested ferrihydrite’s role in Mars’ redness, but a new study has combined laboratory methods with observational data to provide evidence. The study aims to determine the specific iron oxide responsible for the red hue in Mars dust, which could offer insights into the processes that produced the dust and when these occurred.
A team led by A. Valantinas utilized data from various spacecraft, including the European Space Agency’s Mars Express orbiter, ExoMars Trace Gas Orbiter, and NASA’s Mars Reconnaissance Orbiter, Curiosity, Pathfinder, and Opportunity rovers. By analyzing the dust particles on Mars through imaging systems like CaSSIS, the researchers replicated Martian dust in the lab using a mixture of ferrihydrite and basalt. This replica dust was analyzed using X-ray machines and reflectance spectrometers, comparing the lab data with spacecraft observations to draw conclusions.
The study found that ferrihydrite mixed with basalt best matches the minerals observed on Mars, suggesting that Mars rusted earlier than previously thought, indicating a watery past for the planet. This discovery provides valuable insights into Mars’ geologic and climate history, hinting at a more widespread presence of liquid water in Mars’ ancient past than previously believed.
“Valantinas noted that the presence of ferrihydrite on Mars indicates a past environment where liquid water existed, crucial for life to potentially thrive. The study highlights that the formation of ferrihydrite on Mars necessitated the presence of both oxygen, sourced from the atmosphere or other means, and water capable of interacting with iron,” as stated by the European Space Agency (ESA).
ESA’s graphic illustrates Mars’ transformation from a gray, moist planet to the dry, red celestial body we know today. The study didn’t focus on pinpointing the exact timing of the mineral’s formation, yet it suggests that ferrihydrite potentially emerged around 3 billion years ago, during a cooler period, contrasting with the warmer, wetter conditions of millions of years prior.
Valantinas explained, “During a period of intense volcanic activity on Mars, ice-melting events and water-rock interactions likely facilitated conditions conducive to ferrihydrite formation, marking the transition from Mars’ earlier wet state to its current arid environment.”
Speculations suggest that ferrihydrite might not only be present in Martian dust but also within layers of the planet’s rocks. Confirming this theory would require obtaining physical samples of rocks and dust from Mars, a task that NASA and ESA aim to accomplish through the Mars Sample Return program by the early 2030s using the Perseverance rover.
Colin Wilson, ESA’s project scientist for the Trace Gas Orbiter and Mars Express, anticipates that analyzing these samples in laboratories on Earth will offer insights into the quantity of ferrihydrite in Martian dust, aiding in understanding Mars’ water history and potential for life.
The findings pose new mysteries for Valantinas and his team to unravel, such as determining the original source of the ferrihydrite and the precise chemical composition of Mars’ atmosphere during its formation. Figuring out when and where the dust originated could provide clues on the evolution of early Earth-like planets’ atmospheres, according to Horgan.
Horgan elaborated, “Ferrihydrite is commonly found in water-rich soils on Earth, influenced by rapid water movement due to factors like snowmelt or intense short-term rainfall in warmer climates. Evidence of ferrihydrite has been observed in lake sediments at Mars’ Gale crater, explored by the Curiosity rover. To fully decipher this enigma, acquiring a sample of Mars dust for analysis back on Earth is essential.”
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