page_title: Geysers on Mars
section_title: Dry venting
hierarchical_section_title: Geysers on Mars / Geyser mechanism models / Dry venting
caption_attribution_description: English: Schematic sketch of the CO2 geyser hypothesis. Martian south polar layered terrain is overlain by seasonal ice of ~1 m in thickness. Penetration of sunlight to the base of the seasonal deposit causes sublimation from the bottom, leading to a buildup of pressurized CO2 gas. The gas eventually bursts out, entraining dust and leading to the dark fan-shaped deposits. Repeated outbursts from year to year erode the underlying polar layered deposits, leading to the development of "Martian spiders". Polski: Schematyczny szkic hipotezy gejzera CO2 Marsjańskie czapy polarne są przykryte przez suchy lód grubości ~ 1 m. Przenikanie światła słonecznego do podstawy podłoża poprzez taflę lodu (na wiosnę) powoduje sublimację CO2 od dołu, co prowadzi do tworzenia się gazowego CO2 poddawanemu coraz to większemu ciśnieniu. Gaz w końcu wybucha, porywając piasek i kurz, co prowadzi do tworzenia się na powierzchni lodu ciemnych osadów, najczęściej wachlarzowatych. Powtarzające się wybuchy z roku na rok, zaburzają/rozwijają podstawowe polarne warstwy osadowe, co prowadzi do rozwoju "marsjańskich pająków". Romkur 21:32, 16 August 2013 (UTC)
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: Some teams propose dry venting of carbon dioxide (CO₂) gas and sand, occurring between the ice and the underlying bedrock. It is known that a CO₂ ice slab is virtually transparent to solar radiation where 72% of solar energy incident at 60 degrees off vertical will reach the bottom of a 1 m thick layer. In addition, separate teams from Taiwan and France measured the ice thickness in several target areas, and discovered that the greatest thickness of the CO₂ frost layer in the geysers' area is about 0.76–0.78 m, supporting the geophysical model of dry venting powered by sunlight.  As the southern spring CO₂ ice receives enough solar energy, it starts sublimation of the CO₂ ice from the bottom.  This vapor accumulates under the slab rapidly increasing pressure and erupting. High-pressure gas flows through at speeds of 160 kilometres per hour (99 mph) or more;  under the slab, the gas erodes ground as it rushes toward the vents, snatching up loose particles of sand and carving the spidery network of grooves.  The dark material falls back to the surface and may be taken up slope by wind, creating dark wind streak patterns on the ice cap.  This model is consistent with past observations. The location, size and direction of these fans
  are useful to quantifying seasonal winds and sublimation activity.
  It is clear that sublimation of the base of the seasonal ice cap is more than capable of generating a substantial overpressure, which is four orders of magnitude higher than the ice overburden pressure and five orders of magnitude higher than atmospheric pressure as discussed above.
  The observation that a few dark spots form before sunrise, with significant spot formation occurring immediately following sunrise, supports the notion that the system is powered by solar energy.  Eventually the ice is completely removed and the dark granular material is back on the surface; the cycle repeats many times.
  Laboratory experiments performed in 2016 were able to trigger dust eruptions from a layer of dust inside a CO
  ₂ ice slab under Martian atmospheric conditions, lending support to the CO
  ₂ jet and fan production model.
caption: According to Sylvain Piqueux, sun light causes sublimation from the bottom, leading to a buildup of pressurized CO2 gas which eventually bursts out, entraining dust and leading to dark fan-shaped deposits with clear directionality indicative of wind action.[26]
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