While many envision Mars as a desolate red dust ball, recent research indicates the presence of mineral deposits suggesting a warm and wet history for the planet. A dedicated team utilized the Compact Reconnaissance Imaging Spectrometer aboard NASA’s Mars Reconnaissance Orbiter to analyze specific wavelengths of visible and near-infrared light from Martian minerals, allowing for detailed assessments of the planet’s chemical composition from afar.
Previous studies have revealed layered silicate minerals, notably clay, scattered across Mars’ surface. This clay formation occurs when water interacts with rock, documenting the amount and chemical composition of the water involved. Water’s interaction with Martian rocks led to the mobilization of elements like magnesium and iron, transporting them to deeper soil layers, while more stable elements like aluminum remained in place. This natural process, known as leaching, resulted in the creation of two distinct clay layers within Martian geology.
Scientists have proposed two primary hypotheses regarding the formation of these layered clays on Mars. The first suggests that clay was formed through underwater seepage in ancient lakes. The second hypothesis posits that a humid surface environment facilitated the leaching process across the Martian landscape.
To investigate these hypotheses, a team from Purdue University estimated the “true” thickness of Mars’ clay layers using terrestrial methods. Since clay-containing rock layers can appear distorted, they can misrepresent thickness. The team conducted a high-resolution imaging science experiment (HiRISE) to generate detailed elevation maps of the Martian surface, utilizing tools from the Mars Reconnaissance Orbiter. These elevation maps were combined with surface composition data from the Compact Reconnaissance Imaging Spectrometer to create intricate 3D composition maps.
Using these 3D compositional maps, the researchers tracked the exposure of each clay layer and monitored it underground to estimate slope angles. They applied trigonometry to calculate the actual thickness of each clay layer, studying 46 locations on Mars. Astonishingly, they found that the total thickness of the combined clay layers ranges from approximately 20 to 680 feet (6 to 200 meters), averaging about 190 feet (60 meters), equivalent to the height of a 60-story building.
The researchers then explored the extent of clay deposits in a significant ancient Martian valley known as the Great Valley of Mars, specifically the Mawrth Vallis region. This region was chosen for its significant elevation variations and previously collected high-resolution chemical composition and elevation data.
The study determined that if the clay layers were confined to the valley’s bottom where water existed, along with varying thicknesses and boundaries, this would strongly support the “aquatic seepage” hypothesis. Conversely, consistent thickness and widespread layer boundaries would lean towards the “surface seepage” hypothesis, indicating a moist surface environment.
The findings revealed that the clay layer extended beyond the valley’s lowest points, maintaining consistent boundaries over an elevation difference of more than half a mile (approximately 1 kilometer). Consequently, the researchers concluded that the clay layers most likely formed through surface leaching in a moist environment.
These groundbreaking discoveries challenge earlier Martian climate models, which suggested that surface conditions rarely exceeded freezing temperatures. The research team hypothesized that these deposits may have formed gradually over extended periods, despite a generally frigid climate. If Mars’ surface remained frozen most of the time with occasional warmth, this could reconcile their findings with existing climate models.
The researchers noted limitations within their study, especially regarding sparsely sampled locations. Despite their strong evidence for widespread wet environments on early Mars, further detailed research in areas like Mawrth Vallis could refine our understanding of the specific surface conditions under which these clays developed, potentially aligning more closely with Martian climate models.
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Source: sciworthy.com
