In April, the European Space Agency released new images of Mars. In them, resembling spiders that were actually mysterious geological formations. Now, NASA’s Jet Propulsion Laboratory has replicated them on Earth.
The study is a great example of empirical science. It solves the mystery of the so-called “Mars spiders” while providing new insights into the geological processes on the Red Planet that ultimately transformed it into a desert.
Some context. The Mars spiders, scientifically referred to as “araneiform terrain,” are geological formations on the Red Planet. They’re characterized by their crack patterns, which resemble spiders with multiple legs when viewed from Martian orbiters.
They were first observed by Mars-orbiting probes in 2003. They’re primarily located in the southern polar plain on the planet, with some measuring more than 3,200 feet in diameter.
The theory. The Kieffer model provides a theoretical explanation for the formation of these “spiders.” According to this theory, spiders are formed when dry ice (carbon dioxide ice) sublimates during the spring.
In summary, sunlight heats the ground beneath the ice, causing the formation of gas that generates pressure and leads to cracks in both the substrate and the ice. Recently, scientists have validated this theoretical model with empirical data.
Spiders on Mars (left) and those recreated by NASA (right).
The experiment. A team of researchers, led by planetary geomorphologist Lauren Mc Keown, successfully recreated the Kieffer model on Earth.
They used the DUSTIE cold chamber at NASA’s Jet Propulsion Laboratory to simulate the low temperatures (-301 degrees Fahrenheit) and pressures (4-10 mbar) of Mars. The experiment involved condensing CO2 ice on a substrate simulating Martian soil and applying heat from below to mimic the heat of the Sun.
The result. As the dry ice sublimated, scientists observed how carbon dioxide gas seeped into the pore spaces of the substrate, forming a thin layer of translucent ice on the surface.
The gas geysers expelled the dust outward, creating a dark stain. Subsequently, thermal stress cracks formed, resembling a web similar to Mars spiders. These cracks appear to result from CO2 sublimation rather than surface erosion, validating the Kieffer model.
Eureka. The appearance of the cracks was an exciting moment for Mc Keown in the lab. “It was late on a Friday evening and the lab manager burst in after hearing me shrieking. She thought there had been an accident,” she says.
As mentioned earlier, the discovery is a perfect example of empirical science. Additionally, it has encouraged researchers to improve upon it by using simulated sunlight instead of heat to more closely mimic Martian conditions.
What’s next. The team plans to conduct further experiments to understand why the spiders form only in certain areas of Mars and why they don’t seem to increase in number. This could indicate they’re remnants of the planet’s past climatic conditions.
Understanding how these structures form may help the science community better understand Mars’ geology and climatic evolution. Ultimately, everybody wants to prevent Earth from becoming a desert like Mars.
Image | ESA | NASA
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