Scientists have been intrigued by peculiar spider-like formations found on Mars. These formations referred to as spiders or araneiform terrain, which have puzzled researchers since they were first identified in images captured by Mars orbiters in 2003. The term spiders on Mars doesn’t refer to actual arachnids but rather to large spider-like geological formations found on the planet’s southern hemisphere.
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These formations are known as araneiform terrain, consist of fan-like cracks or channels radiating outward from a central point, resembling the legs of a spider. These structures can be quite large with some measuring over half a mile across and featuring hundreds of thin legs.
The mysterious spiders were first discovered in 2003 when NASA scientists studied images taken by the Mars Reconnaissance Orbiter and other orbiting spacecraft. These formations were found in the polar regions of Mars in the southern hemisphere.
The origin of these spider-like formations on Mars remained a mystery for nearly two decades. The peculiar shapes were unlike anything found on Earth.
Early theories speculated that carbon dioxide ice played a role in the formation of these structures, but there was little direct evidence to support this until recent experiments.
These formations are prominent in the southern hemisphere of Mars and cover areas as large as 3,300 feet in diameter. The terrain resembles a series of dark, radiating cracks on the Martian surface that look like a cluster of spiders from above. The term spiders on Mars stuck due to their striking resemblance to arachnids.
Scientists believe that these spider-like formations occur due to a process involving carbon dioxide ice sublimation. During the Martian winter, CO2 ice accumulates on the surface. As Martian spring approaches, sunlight penetrates through the ice, heating the soil underneath.
The heat causes the CO2 ice to sublimate without turning into liquid, creating a buildup of gas pressure beneath the ice. When the pressure becomes too great, the ice cracks, and the gas escapes through vents, carrying dark material with it to the surface. These eruptions leave behind distinctive spider-like patterns etched into the ground.
The explanation for how spiders form on Mars is known as the Kieffer model, which was proposed years ago. In the Kieffer model, CO2 sublimation is responsible for these formations.
However, recreating the exact conditions for this phenomenon has been a challenge for scientists on Earth. According to the model, the spiders appear during Martian spring when sunlight heats the surface beneath the CO2 ice. This heating leads to sublimation, which drives the gas upwards, cracking the ice and forming the spider-like cracks.
After years of effort, NASA scientists have successfully replicated the formation process of the Martian spiders on Earth. A research team led by planetary geomorphologist Lauren Mc Keown conducted this experiment using a specialized chamber at NASA’s Jet Propulsion Laboratory (JPL).
The experiment was conducted in a facility known as the Dirty Under-vacuum Simulation Testbed for Icy Environments (DUSTIE), which mimics the low-pressure, extreme-cold conditions of Mars.
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The DUSTIE chamber is capable of simulating the Martian environment including its extremely low temperatures and pressures (up to minus 301 degrees Fahrenheit).
The research team placed simulated Martian soil known as regolith into the chamber and covered it with a layer of CO2 ice. A lamp was placed beneath the soil to replicate the warming effect of the sun on Mars.
It took numerous attempts before the researchers found the precise conditions for the ice to sublimate and form the distinctive spider-like patterns.
After five years of experimentation, Mc Keown’s team finally succeeded in creating miniature versions of the spiders on Mars. In one of the attempts, the CO2 ice cracked open and gas began seeping out, leaving behind a spider-like pattern on the simulated Martian soil.
Mc Keown described the moment of success as exhilarating with shrieks of joy erupting in the lab. The sight of the spiders forming for the first time on Earth was an achievement for the team.
The DUSTIE test chamber was key to this experiment, as it helped recreate the combination of extreme cold and low air pressure found at Mars’ south pole.
In this controlled environment, researchers cooled and condensed carbon dioxide gas into ice, placing it atop a simulant designed to mimic Martian soil. They then carefully heated the ice, watching as it cracked and released gas, mimicking the process that creates the spider-like formations on Mars.
As the ice heated and sublimated, the trapped CO2 gas erupted out of the soil, leaving behind the araneiform patterns. These results matched the spider formations observed on Mars providing strong support for the Kieffer model.
During the experiment, the team observed the creation of spiders in the simulated soil. The process involved gas plumes bursting through the soil and leaving behind spider-like scars on the surface.
One observation was the formation of cracks between the grains of the soil simulant. This was not part of the original Kieffer model, but it provided insights into why araneiform terrain appears with such detailed legs.
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