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Citizen Scientists Seek South Pole 'Spiders' on Mars
Jet Propulsion Laboratory
October 20, 2016

[Image]
This image shows spidery channels eroded into Martian ground. This image
shows spidery channels eroded into Martian ground. It is a Sept. 12, 2016, example from HiRISE camera high-resolution observations of more than 20
places that were chosen in 2016 on the basis of about 10,000 volunteers' examination of Context Camera lower-resolution views of larger areas.
Image credit: NASA/JPL-Caltech/Univ. of Arizona

Ten thousand volunteers viewing images of Martian south polar regions
have helped identify targets for closer inspection, yielding new insights about seasonal slabs of frozen carbon dioxide and erosional features known
as "spiders."

From the comfort of home, the volunteers have been exploring the surface
of Mars by reviewing images from the Context Camera (CTX) on NASA's Mars Reconnaissance Orbiter and identifying certain types of seasonal terrains
near Mars' south pole. These efforts by volunteers using the "Planet Four: Terrains" website have aided scientists who plan observations with the
same orbiter's High Resolution Imaging Science Experiment (HiRISE) camera. HiRISE photographs much less ground but in much greater detail than CTX.

Volunteers have helped identify more than 20 regions in mid-resolution
images to investigate with higher resolution. "It's heartwarming to see
so many citizens of planet Earth donate their time to help study Mars,"
said HiRISE Deputy Principal Investigator Candice Hansen, of the Planetary Science Institute, Tucson, Arizona. "Thanks to the discovery power of
so many people, we're using HiRISE to take images of places we might not
have studied without this assistance."

Planetary scientist Meg Schwamb, of the Gemini Observatory, Hilo, Hawaii, presented results from the first year of this citizen science project
Thursday at the annual meeting of the American Astronomical Society's
Division for Planetary Sciences and the European Planetary Science Congress, in Pasadena, California.

The type of terrain called spiders, or "araneiform" (from the Latin word
for spiders), is characterized by multiple channels converging at a point, resembling a spider's long legs. Previous studies concluded that this
ground texture results from extensive sheets of ice thawing bottom-side
first as the ice is warmed by the ground below it. Thawed carbon dioxide
gas builds up pressure, and the gas escapes through vents in the overlying sheet of remaining ice, pulling dust with it. This process carves the
channels that resemble legs of a spider.

"The trapped carbon dioxide gas that carves the spiders in the ground
also breaks through the thawing ice sheet," Schwamb said. "It lofts dust
and dirt that local winds then sculpt into hundreds of thousands of dark
fans that are observed from orbit. For the past decade, HiRISE has been monitoring this process on other parts of the south pole. The 20 new regions have been added to this seasonal monitoring campaign. Without the efforts
of the public, we wouldn't be able to see how these regions evolve over
the spring and summer compared with other regions."

Some of the HiRISE observations guided by the volunteers' input confirmed "spider" terrain in areas not previously associated with carbon dioxide
slab ice.

"From what we've learned about spider terrain elsewhere, slab ice must
be involved at the locations of these new observations, even though we
had no previous indication of it there," Hansen said. "Maybe it's related
to the erodability of the terrain."

Some of the new observations targeted with information from the volunteers confirm spiders in areas where the ground surface is made of material
ejected from impact craters, blanketing an older surface. "Crater ejecta blankets are erodible. Perhaps on surfaces that are more erodable, relative
to other surfaces, slab ice would not need to be present as long, or as
thick, for spiders to form," Hansen said. "We have new findings, and new questions to answer, thanks to all the help from volunteers."

The productive volunteer participation continues, and new CTX images have
been added for examining additional areas in Mars' south polar region.
Planet Four: Terrains is on a platform released by the Zooniverse, which
hosts 48 projects that enlist people worldwide to contribute to discoveries
in fields ranging from astronomy to zoology. For information about how
to participate, visit:

http://terrains.planetfour.org

With CTX, HiRISE and four other instruments, the Mars Reconnaissance Orbiter has been investigating Mars since 2006.

Malin Space Science Systems, San Diego, built and operates CTX. The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace
& Technologies Corp. of Boulder, Colorado. NASA's Jet Propulsion Laboratory,
a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, built the orbiter and collaborates with
JPL to operate it. For additional information about the project, visit: http://mars.nasa.gov/mro

News Media Contact
Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278
guy.webster@jpl.nasa.gov

Alan Fischer
Planetary Science Institute, Tucson, Ariz.
520-382-0411
fischer@psi.edu

Peter Michaud
Gemini Observatory, Hilo, Hawai'i
808-974-2510
azangari@boulder.swri.edu

Dwayne Brown / Laurie Cantillo
NASA Headquarters, Washington
202-358-1726 / 202-358-1077
dwayne.c.brown@nasa.gov / laura.l.cantillo@nasa.gov

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