page_title: Geysers on Mars
section_title: History
hierarchical_section_title: Geysers on Mars / History
context_page_description: Martian geysers are putative sites of small gas and dust eruptions that occur in the south polar region of Mars during the spring thaw. "Dark dune spots" and "spiders" – or araneiforms – are the two most visible types of features ascribed to these eruptions.
  Martian geysers are distinct from geysers on Earth, which are typically associated with hydrothermal activity. These are unlike any terrestrial geological phenomenon. The reflectance, shapes and unusual spider appearance of these features have stimulated a variety of hypotheses about their origin, ranging from differences in frosting reflectance, to explanations involving biological processes. However, all current geophysical models assume some sort of jet or geyser-like activity on Mars. Their characteristics, and the process of their formation, are still a matter of debate.
  These features are unique to the south polar region of Mars in an area informally called the 'cryptic region', at latitudes 60° to 80° south and longitudes 150°W to 310°W; this 1 meter deep carbon dioxide ice transition area—between the scarps of the thick polar ice layer and the permafrost—is where clusters of the apparent geyser systems are located.
context_section_description: The geological features informally called dark dune spots and spiders were separately discovered on images acquired by the MOC camera on board the Mars Global Surveyor during 1998–1999.  At first it was generally thought they were unrelated features because of their appearance, so from 1998 through 2000 they were reported separately on different research publications ( and -respectively).  "Jet" or "geyser" models were proposed and refined from 2000 onwards.
  The name 'spiders' was coined by Malin Space Science Systems personnel, the developers of the camera. One of the first and most interesting spider photos was found by Greg Orme in October 2000. The unusual shape and appearance of these 'spider webs' and spots caused a lot of speculation about their origin. The first years' surveillance showed that during the following Martian years, 70% of the spots appear at exactly the same place, and a preliminary statistical study obtained between September 1999 and March 2005, indicated that dark dune spots and spiders are related phenomena as functions of the cycle of carbon dioxide (CO₂) condensing as “dry ice” and sublimating.
  It was also initially suggested that the dark spots were simply warm patches of bare ground, but thermal imaging during 2006 revealed that these structures were as cold as the ice that covers the area,  indicating they were a thin layer of dark material lying on top of the ice and kept chilled by it.  However, soon after their first detection, they were discovered to be negative topographical features – i.e. radial troughs or channels of what today are thought to be geyser-like vent systems.
caption: Close up of dark dune spots obtained by the Mars Global Surveyor and discovered in 2000 by Greg Orme.
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