The spiders that volunteers helped find

Martian 'Spiders' in Sharper Look, Thanks to Volunteers — NASA/JPL-Caltech/Univ. of Arizona
Event image. A sharper look at branching channels, targeted after volunteers examined broader views.
NASA/JPL image-use policy · credited mission imagery, resized to WebP
· Original image source · Image licence

Public image explorers helped choose where a spacecraft looked next.

World: Mars
Case date or period: Image archive · 2009–2018

Look closer

Planet Four: Terrains volunteers examined broad Context Camera views near the south pole. Their classifications helped identify places for sharper HiRISE observations, including branching channels nicknamed spiders.

Follow the evidence

The channels and dark fans develop in a landscape shaped by seasonal carbon-dioxide ice. Follow the scale changes in the images: the striking patterns resolve into troughs and deposits rather than organisms.

A public contribution that changed the view

People outside the mission team helped classify terrain in broad orbital images. Candidate areas then received sharper HiRISE attention. The project page currently marks this classification set complete; the enduring result is a documented path from public observation to new spacecraft imagery.

Testing a formation process on Earth

A 2024 JPL experiment recreated gas plumes and branching disturbances in chilled Martian soil simulant beneath carbon-dioxide ice. The team used reduced pressure and a heater below the sample to test processes in the Kieffer model. Ice forming between soil grains also produced cracking, suggesting an additional mechanism. The researchers proposed further tests with simulated sunlight from above. This laboratory result supports parts of a physical formation model; it is not a recording of an eruption on Mars.

Volunteers widened the search

The team’s 2017 paper reports spider terrain outside the South Polar Layered Deposits, where it had previously been reported as confined. HiRISE follow-up confirmed the volunteer-led identifications. Three quarters of the high-confidence locations in this sample were still within those deposits. That fraction describes the surveyed sample, not all of Mars; the authors explicitly say their coverage cannot establish every geological unit where spiders form. Public classifications helped test where the process can operate.

Read the channels beneath the seasonal surface

The 2009 view exposes channels after seasonal frost has disappeared. The 2018 view shows bright ice and dark deposits instead. They show different places, so this is a comparison of surface conditions rather than a time-lapse of one formation. JPL describes gas escaping from beneath carbon-dioxide ice as a mechanism that carves channels and redistributes dust. The still photographs show the resulting terrain, not the gas moving.