NASA Scientists Simulate Mars's Spider-Shaped Geological Forms in Laboratory

NASA scientists have successfully recreated Mars’s unique spider-shaped geological formations in a laboratory setting, reports Phys. This work confirms that carbon dioxide is involved in the formation of these intriguing features.

Understanding Martian Spider-Shaped Features

Since their initial discovery in 2003 through images captured by orbiters, scientists have admired the artistically intricate spider-like structures in Mars’s southern hemisphere. Each formation can extend over half a mile (1 kilometer) and possesses numerous slender "legs." Known as araneiform terrain, these formations often appear in clusters, creating a wrinkled effect on the Martian surface.

Current theories suggest that these formations arise from processes involving carbon dioxide ice, which is not commonly found on Earth. A new study published in The Planetary Science Journal describes experiments conducted under simulated Martian conditions that replicate these geological processes.

Experiments in Simulated Martian Conditions

"The spiders are strange, beautiful geologic features in their own right," noted Lauren McKeown from NASA’s Jet Propulsion Laboratory (JPL). These laboratory experiments are designed to refine existing models that explain the morphology of these formations.

The experiments support many of the formation theories presented by the Kieffer model. This model posits that seasonal changes, particularly sunlight in winter, heat the ground beneath transparent carbon dioxide ice. The underlying soil then heats up, causing the ice to sublimate into gas, increasing pressure within the Martian ice. Eventually, as gas escapes, it carries with it dark dust and sand from the soil, leading to the development of spider-like marks as the winter ice melts.

Challenges of Mimicking Mars on Earth

Recreating Martian environmental conditions posed challenges for McKeown and her team. They needed to simulate Mars's extremely low air pressure and cold temperatures, reaching as low as -301 degrees Fahrenheit (-185 degrees Celsius). This was achieved by utilizing the Dirty Under-vacuum Simulation Testbed for Icy Environments, or DUSTIE, at JPL.

McKeown expressed her admiration for DUSTIE, highlighting its historic significance and its previous use for testing NASA's Mars Phoenix lander's rasping tool, which analyzed ice near Mars's north pole. For this specific experiment, the team simulated Martian soil within a liquid nitrogen bath, creating similar pressure conditions to those found in Mars's southern hemisphere.

Unexpected Discoveries and Future Plans

One of the unforeseen outcomes of the experiments involved the formation of ice between soil grains, which ultimately cracked the simulant open. This observation suggests a new potential process at play, pointing to the complexity and variability of geological phenomena. Serina Diniega, also from JPL, remarked on how these findings indicate a degree of unpredictability within natural processes.

Looking ahead, scientists plan to repeat the experiments, this time incorporating simulated sunlight to better understand conditions leading to plume formation. Many questions continue to linger regarding these geologic formations. For instance, what determines their presence in various locations on Mars, and why do they not appear to be expanding over time?

For now, laboratory studies bring scientists closer to unraveling the mystery of spiders on Mars. As of now, both the Curiosity and Perseverance rovers navigate regions of the red planet distant from these peculiar southern formations. Unfortunately, the Phoenix mission, which landed in the northern hemisphere, was short-lived due to harsh polar conditions.

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