#93 March 1996
Section 184.108.40.206.093.of the Artemis Data Book
PER-ma-frost: [from perma(nent) + frost] perennially frozen subsoil. Also called pergelisol.
We find permafrost mostly in circum arctic lands of Alaska, Canada (Northwest Territories, northern Quebec, northern Labrador), Greenland, Iceland, Scandinavia (Norway, especially), and Russia-Siberia. Permafrost is the soil condition that manifests itself in "tundra" type no-root or shallow-root vegetation.
Permafrost forms in ground water areas through gradual transition to ever more severe winters and ever shorter and cooler summers. The deeper the ground water penetrates, and the greater the water content per volume of soil, the thicker and richer the permafrost layer.
There is abundant evidence from high resolution Viking photos of landforms for which the only plausible explanation is that they were formed by water: tear drop shaped islands in the middle of large valleys, relic beaches and ancient shorelines, wave-sculpted dry lake and sea shore bottoms, deltas and estuaries, flood-carved channels. From such evidence, it has become clear that Mars even sported a respectable northern hemisphere ocean that once covered more than a third of the planet to respectable depths. Not all of this water could have evaporated or sublimated into space. Archaic water-saturated lake and sea bottoms should have retained their water content as the climate got colder and the ground froze to deeper and deeper levels.
The likeliest areas of significant permafrost deposits are the ancient northern ocean bottomlands, deep major impact basin bottoms like Hellas and Argyre, and canyon bottoms (especially the outflow areas like the Ares Valley landing site for the Mars Pathfinder lander. Unfortunately, this lander is not providentially equipped to test for permafrost underfoot. It is typical that the kind of knowledge most needed to assess settlement feasibilities is low on the priority list of planetary scientists interested primarily in scratching the itches of their own narrow scientific curiosities. Both Vikings likewise landed in areas in which we might expect to find substantial permafrost deposits, a condition that went untested.)
Permafrost could have formed in adjacent areas not covered by standing water through the lateral spread of ground water, and in still other areas if subject to seasonal rainfall.
On Earth, (a) permafrost renders the land agriculturally unproductive, although tundra lichens and other vegetation is sufficient to maintain a large wildlife population of caribou, rabbits, and other hardy arctic fauna. (b) Buildings must be set on bedrock or thermally isolated from the ground, commonly by use of stilts made of materials with low heat conductivity, along with effective use of insulation to prevent heat radiating from the bottom of the building to the frozen soil below. The stilts should raise the underside of the building high enough above the ground to allow free air and wind circulation. (c) Road building creates special problems, witness the special measures that had to be taken during the construction of the Alaska Pipeline.
On Mars, seasonal thaws may not be a problem at first, but may become less and less rare as human activities, planned and unplanned, lead to a significant warming of the Martian climate. (a) For this reason, outposts in permafrost areas will be especially challenging to build and maintain. Settlement may be limited to areas of patchy permafrost, with construction held to frigid but not ice-saturated soil and rock areas. (b) Only those areas where the 'topsoil' is 'active', i.e. thawing seasonally, will be colonizaible by bioengineered Mars-hardy plant varieties developed through an aggressive redhousing program.
|Mars outpost on stilts- insulated|
|Mars subsurface outpost - insulated|
|Mars subsurface outpost in "patchy" area|
Whichever method we use to extract the ice-melt, it may be necessary, if the water proves to be saline, to distill the melt to purify it of salts (and possibly heavy metals). A few "ground truth" cores taken by rover drilling probes would soon establish just how fresh or how brackish the permafrost ice is, and whether it varies in quality from place to place.
Excess water produced by an outpost's local permafrost tap may then be trucked, or air-lifted, or eventually pipelined to other less advantaged settlements and outposts. Thus, water could well be the first real intra-Mars trade commodity. (A futures market, anyone?)
Other most options for providing water needed for drinking and hygiene, agriculture and life support, processing and manufacturing do exist:
One or both of these options can serve "ice-dry" areas of Mars.
Because extensive permafrost zones are found here on Earth (some continuous, some discontinuous, some patchy), we have an ideal opportunity to fly the needed radar instrument package in polar Earth orbit to both test how well it can detect permafrost and to properly calibrate the instruments by checking their readings with actual data on the ground, so we will have greater confidence in interpreting the readings we get in flying an identical instrument package around Mars. We need to determine how well depth of the layer below the surface, ice content percentage, and thickness of the deposits are indicated in the readings, and whether differences in salinity or other factors affect the data points we get.
If flown alone (not with lavatube radar) as co-op U.S.-Russian mission, Bering (Russian-born explorer of Alaska, Vitus Bering) might be a good name for the probe. Mars Permafrost Mapper would be an alternate choice.
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