What can Arctic rocks teach us about life on Mars?

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Within the frozen landscapes of the Canadian Arctic, there exists a fascinating geological phenomenon: gossans – mounds of oxidised minerals that hold within them the clues to ancient geological processes. These formations, created through the weathering of sulphide minerals, offer a window into the past, providing insights not only into Earth’s history, but also into the history of other planets. 

Éloïse Brassard, a PhD student at the Université de Sherbrooke, is working on the T-MARS project, which aims to study gossans as analogues to similar formations on Mars. 

“Within the T-MARS project, my research is focused on developing a satellite detection method that could be used to identify gossans on Mars,” explains Éloïse. As she develops this method, Éloïse is also studying the mineralogical and geochemical composition of the Arctic gossans in her study area in Canada. 

How can studying environments on Earth impact space exploration? 

Studying environments on Earth is essential for improving space exploration. “According to the experts, given the excessive costs, risks and technological challenges associated with space exploration, the most viable alternative is to use the Earth to simulate other planets and moons as closely as possible,” says Éloïse. “Environments on Earth that present geological or environmental conditions similar to those found on other planetary bodies are known as ‘analogue sites’.” These sites provide researchers with the opportunity to conduct comparative studies, drawing parallels between Earth’s features and those observed on distant planets and moons. 

Why is the Canadian Arctic an ideal model for Mars? 

The Canadian Arctic has striking similarities to many environments and geological conditions found on Mars. “The environments on Earth that are most similar to the extremely cold and dry conditions that we expect to exist on Mars are terrestrial polar deserts,” says Éloïse. “The Canadian Arctic therefore provides the perfect opportunity to examine the physical and biological processes that take place in these environments, and to develop and test new technologies that may play a part in future Mars missions.” For example, geological field studies conducted on Axel Heiberg Island, a focal point of research in the region, have shown that its geological features closely resemble those found on Martian volcanic terrains. 

Gossans are found across various climatic zones on Earth and are created when sulphide minerals in rocks react with oxygen and water. “Gossans generally range from a few metres to 1-2 km in size in the Canadian Arctic,” says Éloïse. “They may also exist on Mars since the environmental conditions were once favourable for their formation.” While gossans on Mars remain a hypothesis, their potential existence emphasises the importance of understanding the mineralogical and geochemical composition of gossans on Earth. 

What clues do gossans hold about ancient life? 

Beyond their geological intrigue, gossans have a remarkable capacity for preserving biosignatures – traces of past or present life forms or biological processes. “Gossans can preserve biosignatures in the form of mineral patterns, such as iron oxide filaments, or chemical traces, such as lipids from cell residues,” explains Éloïse. 

The presence of iron-rich minerals within gossans acts as a preservative, prolonging the survival of these biosignatures by limiting enzyme activity that would otherwise degrade them. Moreover, certain sulphate minerals, like jarosite, found in Arctic gossans and in some places on Mars, serve as indicators of ancient environmental conditions, particularly the presence of liquid water at specific geological epochs. 

“As the Earth is the only place where traces of life are known to exist, it is essential to study biosignatures in order to understand how they were created and preserved,” says Éloïse. 

How is Éloïse analysing gossans? 

Éloïse uses a multifaceted approach to study gossans, beginning with the collection of samples from the Canadian Arctic. She then analyses these samples, with a focus on measuring their reflectance – the proportion of solar radiation reflected for each wavelength in the electromagnetic spectrum. Analysing the samples in this way allows Éloïse to identify which minerals they contain and capture their distinct ‘signatures’, which she uses to locate and map gossans from satellite images. 

However, this method has its limitations. A primary challenge lies in the spatial resolution, or the level of detail, provided by satellite images. “With current technologies, multispectral images with good spatial resolution contain less spectral information – fewer wavelengths for which reflectance is known,” explains Éloïse. “This causes the detection of false targets, which have a signature similar to gossans in the available wavelengths.” 

To overcome this issue, Éloïse uses hyperspectral images which contain more information from across the electromagnetic spectrum. These images have lower spatial resolution and can look blurry, but they enable Éloïse to distinguish gossans from false targets. This hybrid approach enables the precise mapping of gossans by combining the detailed spatial information of high-resolution multispectral images with the spectral richness of hyperspectral images. 

What is next in gossan exploration? 

“The next steps are to apply our remote sensing method to other gossan-rich regions in the Canadian Arctic to validate the results and reduce uncertainties,” explains Éloïse. “We will then test this method on satellite images of Mars, potentially identifying areas with properties similar to terrestrial gossans, which would be prime targets in the search for traces of ancient, extra-terrestrial life.” 

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