Arctic and Antarctic Analogs for Liquid Water on Mars
One of the things that perplexed the researchers who made the announcement (one claimed that he had been “dragged kicking and screaming” to the conclusion) was the fact that the apparent evidence of active subsurface water was found near the poles of Mars – not near the equator. Mars is thought to have permafrost deposits distributed on a global scale. They are thickest at the poles with an estimated depth of 2 kilometers. Planetary scientists had suspected that there might be some liquid water under the surface of Mars. The models that had been created used volcanic heat sources to create and maintain liquid water. However, that is not the model operating in these newly discovered polar features. One possible answer may lie in the Canadian arctic. Dr. Chris McKay from NASA Ames Research Center made a presentation on two springs located on Axel Heiberg Island at the recent Mars Society convention in Toronto. Axel Heiberg Island has hosted a number of researchers over the years. Most of them have been housed at the McGill Axel Heiberg Island Station located near the head of Expedition Fiord, on the west coast of Axel Heiberg, 8 km from the sea. As the water flows out of these springs it spreads out, cools, and eventually freezes. As it freezes it also evaporates, a carbonate mineral deposit or “travertine” is left behind, These springs are inhabited by iron-oxidizing bacteria. Any bacteria present in the outflow eventually become trapped and fossilized as these travertine deposits form. McKay suggests that the spring water features recently discovered on Mars by Malin et al be reexamined more closely for evidence of travertine deposits – and fossils. When these springs were discovered on Axel Heiberg, the question quickly arose as to their origin given that no obvious geothermal heat source was present. McKay hypothesizes that these springs are the result of the presence of salt deposits or “diapirs”. The region where these springs are found was once the bottom on an ancient sea bed. Over time, salt deposits formed. According to McKay’s model, the water that feeds these springs originates very deep within the Earth and moves upward through these salt columns to the surface, loosing heat along the way. The water in these springs is very salty as a result – 5 to 10 times as salty as sea water. The presence of salt in this water depresses the vapor pressure and the freezing point allowing the water to remain in a liquid state all year round – or at least until it reaches the surface. The model McKay has developed would also explain how liquid water could exist very close to the surface of present day Mars. On Mars, given the very low atmospheric pressure coupled with low temperatures, liquid water faces the dual risk of boiling as well as freezing. Water rising through a salt column on Mars could accumulate sufficient salt concentration to offset the tendency to boil and freeze – again, at least, as the water arrives to a location close to the surface. Eventually, this water will freeze. According to McKay, it would be expected to leave large salt deposits in outflow features – something spacecraft could be sent to look for. Given the observed features on Earth and the apparent observation of similar features on Mars, McKay noted the usefulness of terrestrial analogs as a means whereby Martian features can be better understood. Recent research tends to add credence to the possibility that large oceans once existed, that salt deposits could exist on Mars, and that substantial amounts of water could still be present very close to the surface of Mars. In June 2000, researchers at the University of Arizona announced that “a recent analysis of the interior of a 1.2 billion-year-old Martian meteorite known as the Nakhla meteorite has shown the presence of water-soluble ions that are thought to have been deposited in cracks by evaporating brine.” The finding, according to the release, “indicates that ancient Martian oceans had a chemical composition similar in variety and concentration to Earth oceans.” A few days later, an announcement from the American Geophysical Union said that “the crust of the planet Mars may hold two to three times more water than scientists had previously believed. This finding is based on a study by Dr. Laurie A. Leshin of Arizona State University comparing the amount of deuterium, an isotope of hydrogen, found in a meteorite of Martian origin to the amount found in the Martian atmosphere.” These lakes are covered with ice that is a dozen meters thick. Despite this covering, enough light gets through to allow photosynthetic algae to thrive. McKay also noted that while it is dim, there is enough light present for divers to operate without the use of flashlights. Over time, the algae in these lakes form thick algal mats. While sunlight does penetrate the ice, it is not the energy source responsible for keeping water liquid. Rather, this energy is provided by the latent heat resident within the liquid melt water that flows into these lakes for a few days every year. This may not seem like enough energy to create a stable ecosystem albeit a simple one. However, given the long term stability of the Antarctic climate, simple ecosystems can form and remain viable for extended periods of time. McKay feels that the fact that life can exist in polar environments on Earth lends credence to the search for possible locations on Mars – even if they no longer harbor life. McKay sees one location on Mars which he thinks was once like the ice covered lakes in Antarctic – Gustav crater. Satellite photographs show a channel carved by fluid emptying into the crater. Ridges and other features associated with a delta can be clearly seen. McKay feels that such a location might be a smart choice for a visit at some point. When this happens, the spacecraft (or humans) should be equipped with instrumentation capable of searching for carbonate depositions or even the organic remnants of previous life. The 1996 announcement regarding possible fossil organisms within the ALH 84001 Mars meteorite gave us tantalizing evidence that life might have existed on Mars billions of years ago. This discovery regarding liquid water near the surface of Mars provides tantalizing evidence that the conditions supportive of life could exist on Mars today. We have a number of locations on Earth that are being used to try and understand how liquid water may still be at work very close to the surface of present day Mars and what this has to say regarding the potential for life (past or present) on Mars. Related Links ° Image archive of the Springs at Colour Peak ° Perennial spring occurrence in the Expedition Fiord area of western Axel Heiberg Island, Canadian High Arctic [Poster Abstract], Canadian Journal of Earth Sciences ° Geomorphic and hydrologic characteristics of perennial springs on Axel Heiberg Island, Canadian High Arctic [Abstract], Canadian Journal of Earth Sciences ° McGill University’s Axel Heiberg Island Station, Mars On Earth 2000 ° Mars May Be Even Wetter Than It Was Last Week, SpaceRef ° Mars Once Had Salty Oceans – Just Like Earth, SpaceRef ° Mars, Like Earth, is not a Simple Planet to Understand, SpaceRef Background Information ° Life on Mars, Whole Mars Catalog ° Life in Extreme Environments, Astrobiology Web ° Mars may hold twice as much water as previously thought, American Geophysical Union ° Meteorite research indicates Mars had Earth-like oceans, Arizona State University ° Liquid Water on Mars: The Story from Meteorites, Hawai’i Institute of Geophysics and Planetology ° Meteorite Found to Contain Water From Our Solar System’s Infancy ° Mars Global Surveyor Provides Evidence of Ancient Martian Oceans, SpaceRef ° Brown geologist finds evidence supporting ancient ocean on Mars, press release
In June 2000 the world got another dose of Mars hysteria similar, but more limited in amplitude, to the attention that accompanied the ALH84001 Mars meteorite announcement in 1996. The more recent announcement concerned the discovery of what certainly appears to be the action of liquid water just under the surface of Mars. Moreover, it would seem that this is a rather recent phenomenon – one that may well be happening today.
Dr. Wayne Pollard from McGill University and a group of associated researchers (including McKay and Dale Andersen from the SETI Institute) discovered two unique springs on Axel Heiberg. These springs run year round and emerge out of permafrost that is approximately 1/2 kilometer thick. These are the only two springs of this type known in the world. The temperature of the water in these springs remains constant all year regardless of the external air or ground temperature which can range from 15 to -40C. 
The arctic is not the only place wherein features on Earth may resemble locations on mars. There are “dry valleys” in Antarctic, more or less devoid of thick snow cover, that contain ice-covered lakes. These valleys are the driest places on Earth. These lakes contain liquid water underneath an ice layer on a year long basis. McKay has also visited these lakes with an eye on possible analogs to Martian features.
° Life in Extreme Environments, SpaceRef Directory
