The Spiders from Mars isn’t just the name of David Bowie’s backing band in the 1970s – it’s the nickname given to mysterious formations on Mars that resemble creepy black arachnids.
These ‘araneiforms’ (Latin for ‘arachnid’) were first observed 20 years ago, but astronomers have finally determined that they are caused by carbon dioxide vapor escaping from cracks in arctic ice in the spring.
Researchers were able to establish this long-suspected hypothesis by simulating conditions from the surface of Mars in a simulator.
By lowering and lifting blocks of dry ice – essentially frozen CO2 – onto gravel beds, they saw the same spindly patterns appear on the surface.
Scroll down for video
This 2018 photo, taken by NASA’s Mars Reconnaissance Orbiter, shows’ spiders’ starting to appear from the surface of Mars’ south pole
When sunlight falls through the translucent ice that covers the poles of Mars each spring, it heats up the loose rock beneath and builds pressure.
That pressure causes the ice to crack and the evaporated carbon dioxide to forcefully escape, blowing sand and grit into the air.
The granular material then settles on the ice in shapes that resemble tree branches or spindly spider legs.
The pressure is so strong that the CO2 actually sublimes, or changes directly from a frozen solid to vapor.
Troughs across the surface of Mars that appear in the spring are called ‘araneiforms’ because of their spider-like appearance. New research has confirmed the long-held theory that these patterns are caused by sunlight heating the ice and allowing CO2 vapor to pass through. The sand and dirt displaced by the carbon plume ends up in branch-like patterns that can be over 3,000 feet wide
To test the theory, researchers lowered a block of frozen carbon dioxide or dry ice onto a bed of gravel in a chamber simulating Mars’ atmospheric conditions. When the block was removed, the spindly patterns were clearly visible
Araneiforms have been captured by the Mars Reconnaissance Orbiter and other satellites, and the theory that they are caused by escaping CO2 “ has been widely accepted for over a decade, ” said Lauren McKeown, an Open University researcher and lead author of a published study. in Scientific Reports.
“But so far it has been placed in a purely theoretical context,” she added.
To test the theory, McKeown and colleagues from Ireland and the UK recreated the atmospheric pressure of Mars at the Open University Mars Simulation Chamber in Milton Keynes, England.
The finer the sediment used in the experiment, the more ramifications the patterns had, the authors reported
The Mars simulation room at the Open University (photo) can simulate the atmospheric conditions of Mars
They drilled holes in blocks of dry ice, the solid form of carbon dioxide, and hung them over beds of various sizes.
The pressure in the chamber was lowered to approximate the atmosphere on Mars, after which the dry ice on the sandy surface was lowered.
When the block reached the surface, the CO2 immediately turned from solid to gas and vapor escaped through the hole.
A block of dry ice is lowered onto a granular bed in the simulator
In each experiment, when the block was lifted, a spider-like pattern was left.
The finer the sediment used, the more ramifications the patterns had, the authors reported.
“The experiments immediately show that the spin patterns we observe on Mars from Earth orbit can be cut out by the direct conversion of dry ice from solid to gas,” said McKeown.
Araneiforms, which can be up to 3,300 feet wide, are not found anywhere on Earth.
That’s because there is so much less carbon dioxide on our planet: The atmosphere on Mars is more than 95 percent CO2, which also includes much of the ice and frost that form at the poles of Mars in winter.
McKeown called the discovery “exciting,” as scientists are finally beginning to understand more about how the surface of Mars changes every season.
The findings could also be helpful to NASA, which focused on human missions to Mars in the 2030s.
‘This innovative work supports the emerging theme that the current climate and weather on Mars has a significant impact not only on dynamic surface processes, but also on any future robotic and / or human exploration of the planet,’ said Mary Bourke, a geomorphologist at Trinity who supervised the investigation.