Clay mounds and hills found on Mars tell us more about water on the Red Planet

The northern plains of Mars, marked by thousands of mounds and hills, hold significant evidence of the planet’s watery past. 

According to a recent study, the formations represent remnants of an ancient, water-altered landscape that has been almost entirely eroded.

This region, roughly the size of the United Kingdom, provides critical insights into Mars’ geological and climatic history.

Mapping Mars’ northern plains

Dr. Joseph McNeil, a researcher at London’s Natural History Museum (NHM), and collaborators at The Open University conducted a detailed analysis using high-resolution imagery and compositional data gathered by Mars orbiters. 

The research was focused on mounds up to half a kilometer tall, which the experts identified as eroded remnants of ancient highlands. 

Over billions of years, these highlands receded by hundreds of kilometers, profoundly shaping the Martian terrain. This erosion delineates the planet’s low-lying northern hemisphere from its elevated southern hemisphere.

“These mounds are incredibly exciting because they preserve the complete history of water in this region within accessible, continuous rocky outcrops,” McNeil said. 

“They are a prime location for future missions aimed at uncovering whether Mars ever had an ocean and whether life could have existed there.”

Layers of Martian history

The study revealed that the mounds are composed of stratified layers of clay minerals. These layers were formed through prolonged interactions between water and rock, suggesting Mars once had a stable, wet environment.

The mounds’ geology presents three distinct eras. Older non-clay layers lie beneath the clay deposits and represent a pre-aqueous period in Martian history.

Clay mineral layers were formed by water-rock interactions over millions of years. These layers capture the history of Mars’ wet conditions.

Younger non-clay layers overlie the clay deposits, marking a shift to a drier climate.

The clay layers’ positioning between older and younger deposits underscores Mars’ complex geological history and its transition from a wet to a more arid planet.

Links to future Mars missions

The findings also connect these mounds to Oxia Planum, a region of great interest due to its geological similarity and proximity. 

The European Space Agency’s Rosalind Franklin rover, set to launch in 2028, will explore Oxia Planum for signs of past or present life. The study reinforces the significance of this region as a potential record of Mars’ capacity to support life.

This connection between the northern mounds and Oxia Planum strengthens the case for these areas as critical targets for exploration. Insights gleaned here could reveal whether Mars had an ancient ocean and provide context for the planet’s shift to the dry, desolate conditions we see today.

A model for Earth’s ancient past

Mars’ preserved geological record offers parallels to early Earth, a time before plate tectonics reshaped our planet’s surface.

“Mars is a model for what the early Earth might have looked like, as its lack of plate tectonics means that much of its ancient geology is still in place,” McNeil noted. “As more missions visit the red planet, the more we’ll be able to dig into our own planet’s history to work out how life began.”

The study aligns with the NHM’s Planetary Origins and Evolution research theme, which aims to explore the processes shaping Earth and its neighboring planetary systems. 

This research not only sheds light on Mars’ past but also offers broader implications for understanding planetary evolution and the origins of life in the solar system.

Unraveling the mysteries of Mars

The discovery of water-rich mounds on Mars provides a unique window into the planet’s wetter, potentially life-supporting past. With future missions like the Rosalind Franklin rover on the horizon, the study serves as a crucial stepping stone in the quest to unravel Mars’ mysteries.

From the clay layers holding the secrets of ancient water to their implications for understanding Earth’s early environment, these findings emphasize the interconnectedness of planetary research. 

As McNeil and his team continue to investigate, the mounds stand as a testament to Mars’ dynamic history and its potential to unlock answers about the evolution of life.

The study is published in the journal Nature Geoscience. 

Image Credit: ESA/TGO/CaSSIS, NASA/JPL/MSSS/The Murray Lab

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