Billions of years ago, when Mars was young and dynamic, its crust may have harbored hot, water-rich environments—potentially cradles of microbial life. Now, new research unearthed traces of this ancient water embedded in Martian zircon crystals, offering tantalizing hints about the Red Planet’s watery past.

Zircon is one of the most resilient minerals, capable of withstanding billions of years of wear and tear, including massive collision impacts. Often called a time capsule, zircon encases trace elements that reveal its geologic history. Analyzing such ancient zircons can unlock secrets about the environments they formed in—including the presence of water.

The study analyzed zircon from the meteorite Northwest Africa 7034 (NWA 7034), a unique rock containing some of the oldest known Martian minerals, including 4.45-billion-year-old zircon. Meteorites such as this one are expelled from their home on Mars by strong impacts and can reach other celestial bodies, like Earth.

By employing advanced tools like scanning electron microscopy and atom probe tomography, scientists uncovered a fascinating feature: intricate growth zones within the zircon, marked by alternating bands of iron, aluminum, and sodium—hallmarks of hydrothermal activity.

Using high-tech instruments, including scanning electron microscopy and atom probe tomography, scientists uncovered detailed growth zones within the zircon. These zones revealed alternating bands rich in elements like iron, aluminum, and sodium. These are markers of hydrothermal processes — hot water activity. In fact, this elemental zoning mirrors features in terrestrial zircons formed in the presence of water, suggesting that similar processes shaped the early Martian crust.

“We used nano-scale geochemistry to detect elemental evidence of hot water on Mars 4.45 billion years ago,” says Dr. Aaron Cavosie from Curtin’s School of Earth and Planetary Sciences. “Hydrothermal systems were essential for the development of life on Earth and our findings suggest Mars also had water, a key ingredient for habitable environments, during the earliest history of crust formation.

The zircon’s internal structure also contains nanoscale inclusions of magnetite, a mineral that forms in oxidizing and watery conditions. All in all, this is a strong indication that Martian zircons grew within hydrothermal systems, where water was abundant and hot enough to dissolve and transport elements during the planet’s infancy.

Hot water

Hydrothermal systems are extremely intriguing because here on Earth, they’re havens for life. On our planet, these systems teem with microbial communities that thrive in high-temperature, water-rich environments. Could Mars have had the same type of communities, billions of years ago? The question is still open.

The study also touches on Mars’ magnetic history. Magnetite inclusions may offer clues about a time when Mars still had a magnetic field—a vital shield against harmful solar radiation. Understanding this timeline could shed light on the transition from a planet with active geology and water to the arid, frozen landscape we see today.

However, to establish this timeline, we’d need plenty more samples. Right now, we don’t know how widespread these hydrothermal systems were, nor how common magnetic minerals were. But the new study contributes to an already impressive body of evidence of an ancient watery Mars.

The presence of water early in Mars’ history is well-documented through its fluvial features and mineral deposits visible from orbit, yet direct evidence from the planet’s crust has been elusive. This study provides that missing link, even from here on Earth. The findings suggest that liquid water persisted long enough to create chemically dynamic environments in Mars’ crust.

The implications of this discovery extend beyond Mars. It suggests that hydrothermal water may be more common on rocky planets than previously thought. In fact, hydrothermal activity may be a common thread that connects the geologic histories of many terrestrial planets, which is important because where there’s water and heat, the potential for life cannot be ignored.

The finding is also important for future missions to Mars, particularly sample-return missions. Knowing where to look and what to look for is essential, as current rovers can’t cover too much ground looking for samples

“This new study takes us a step further in understanding early Mars, by way of identifying tell-tale signs of water-rich fluids from when the grain formed, providing geochemical markers of water in the oldest known Martian crust,” Cavosie concludes.

Journal Reference: Jack Gillespie, Zircon trace element evidence for early hydrothermal activity on Mars, Science Advances (2024). DOI: 10.1126/sciadv.adq3694