Mars Analog and Geomorphology Institute*


Contact Information:

John Arfstrom


This site is under construction.

*MAGI is in the concept phase. 




Nitrogen glaciers flowing on Pluto! On Earth its water ice that is stable. On Mars its water ice and carbon dioxide ice. On Titan its hydrocarbons. On Pluto its nitrogen. These image of Pluto are most similar to images of Mars where ice ponds inside craters, valleys, and other low lying areas. One might think of ice as one thinks of various liquors - they all do pretty much the same thing yet have various differences of origin and taste (please don't try tasting anything other than water ice!).

A point regarding the speculation about thick nitrogen ice riding on liquid nitrogen is that water ice is less dense than liquid water and thus floats to form ice-covered bodies of water. But, if nitrogen ice is denser than liquid nitrogen at the same pressure, would not the ice sink? However there are complications such as the geothermal gradient, frictional heat of ice deformation and basal sliding, and the increasing pressure with depth to factor in to the logic (science) of glaciers. Scientist use phase diagrams that have axes representing pressure and temperature (and sometimes other complications) to chart-out the solid, liquid, and gas stability of a substance.

An example of the icy complications is how the ice of water-ice glaciers on Earth (and Mars) melts at whatever depths the "pressure melting point" is reached (where liquid water is stable), which can result in subglacial ponding where ice is stagnant enough and drainage of water is restricted, or basal melting (where a glacier is in contact with the ground) of "warm-based" glaciers that causes a glacier to slide on its base and so flow more quickly than by deformation of the ice alone. The basal melting of glaciers also limits the thickness of a glacier by speeding ice down-glacier, and by transferring melted ice down-glacier via subglacial stream networks, sometimes forming tunnel valleys and eskers in the process.

Where nitrogen ice is stagnant on Pluto, basally generated liquid nitrogen might rise to the surface were it not for the pressure melting point of nitrogen, which determines the limits where liquid nitrogen can exist, as it does with water ice on Earth. However, if enough liquid flows from the area of stability at depth, the heat transfer issuing from the flow itself may keep a channel open to normally unstable areas, perhaps even the surface. There is one other wrinkle to consider in this though, because, in some cases, a substance may undergo a pressure-induced atomic or molecular rearrangement that results in a different density phase. And, sometimes other substances like other ices, salts, gases, or other impurities can alter the more basic predictions. To solve these riddles we must consult the literature and run experiments, computer models, and our imagination supercomputer.



This frozen region is north of Pluto’s icy mountains, in the center-left of the heart feature, informally named “Tombaugh Regio” (Tombaugh Region) after Clyde Tombaugh, who discovered Pluto in 1930.

Large-scale methane contraction polygons and methane-thermal eruptions?What the heck? Mounds in geometric cracks? Could they be Polygons and Pingos? They are found in extreme-cold/low surface ice environments on Earth. Polygons form through surface expansion and contraction and are usually small in scale (about a meter), and pingos form through the concentrations of ice that rise to the surface due to its natural buoyancy relative to denser rock, and are many tens of meters across. What liquid would be a good candidate for supporting polygon formation and making pingos on Pluto? Remember that hydrocarbons (methane, ethane, and propane) take the place of water on Titan in that it is stable in all three phases of matter - liquid, gas, and solid - and so creates many of the same geological and geographic features. Pluto may be an arctic analog based on hydrocarbons.

Another possibility is that the cracks represent some sort of large-scale desiccation phenomenon. It should also be noted that water ice expands relative to its liquid state. This property of water is rather unique in the physical world and causes ice to float and gives water the ability to pry and erode rock upon freezing. Most other liquids actually become more dense upon freezing and sink. Could the freezing of hydrocarbons lead to a contraction-based, desiccation-like effect? Might internal heat of impact cause eruptions of hydrocarbons in a fumarole or hydrothermal surface outflow-like fashion that would more likely find its way up through the contraction-fractures and lower elevations of the troughs of the contraction-polygons? In that case the geology would represent large-scale hydrocarbon contraction polygons and hydrocarbon-thermal eruptions.

Perhaps what happened here it that a major impact caused major resurfacing of Pluto resulting is a hydrocarbon-rich, smooth surface, and the polygonal and pingo-like features resulted the modification of that hydrocarbon-rich surface by near-surface cooling and contraction and deeper heat-driven eruptions of liquid hydrocarbons.


I met Clyde Tombaugh at a star party in the Keys of Florida. What a perfect place to observe the heavens it was. Far from the city lights and with a horizon that reached the sea. It gave the grandest views a land lubber could want. Funny that the mission is named New Horizons, but not inappropriate. For although they voted it a planet not, Pluto is the most important and the launching point of a new horizon of discovery of fascinating worlds. As Madagascar is in no way diminished by Africa, and a world of unique wonders and the only home of lemurs, so too will Pluto fascinate the discoverers of our age and forever hence.


On the depression with the peak: is it theoretically possible for a colliding object to "soft-land" on the surface of Charon so as to cause a minor splash effect, with the impactor retaining some of its form? Normally due to the high speeds of impactors, the impactor is largely disintegrated along with the material excavated to make a crater. But, if the impactor "settled in" as opposed to slamming in, it might create this sort of feature. It is hard to imagine an impactor colliding slowly enough if its origin were directly from orbit, but if the impactor were a secondary block of ejecta from another impact on Charon, it might just be able to soft-land and splash out some adjacent material because of lower velocity and create the "peak in a depression" feature on Charon. This is still probably a stretch, but it might make for a neat test for computer impact simulation programs.


Two things on this image. First is that the eye (brain actually) can invert the image so that to some viewers the circular object may appear as a shallow pit with snake-like or ridge-like features, while to others it may appear as a mound or dome with valleys or glacier-like troughs (they are rather u-shaped unlike water carved valleys) eroded through it. The latter visualization is the correct one. You can try to rotate the image 180 degrees to see if the sudden reorientation of shadows triggers your brain's 3-D interpretation of the topography to invert for you. The brain evolved this 3-D enhancement capability to better perceive the topography of distant vistas, but, like with color vision, not all people enjoy this gift to the same degree. Imagine walking towards what appears to be a valley or basin to you only to find that it is actually a ridge or mountain! Images like the one above are a bit ambiguous and lack reference clues, so the brain is more easily tricked than with a familiar Earthly vista. Also, stereoscopic images of Mars and other surfaces can allow those to see in 3-D what may otherwise appear 2-D, and can greatly enhance the "vertical exaggeration" of the topography for those who already process a single image in 3-D.

Secondly, as a result of all the recently acquired hi-resolution images of Mars, research is currently on a reversal of course (or at least a reevaluation) as to the favored interpretation for the so-called outflow channels and related features, moving back to a glacial interpretation from the popular mega-flood interpretation (in my opinion). And, where there is doubt, you can bet that the volcanic camp will offer its interpretations as well, as the NASA scientists who conveyed this story to the media have slanted. With this in mind, I would not rule out that the formation of the surrounding textured flat terrain has resulted from the ablation of an ice sheet associated with the mound's erosional dissection.


I was thinking that the overall pattern might be consistent with an impact of a fractured bolide, but the major bright spot is not quite circular and is possibly more than coincidentally centered on the relatively large crater it is located in. I'm guessing that the central part of the large crater that the bright spots are located in might have some relationship to the formation of the bright spots, based solely on the unlikely odds of this "bullseye" geography. This would not directly explain the other nearby spots, but it might be a clue as to a formation mechanism related to the crater itself, such as the latent heat of impact resulting in Ceres-style fumaroles.

Although light seems to be emanating from the surface, that is really an affect of the flaws in the camera imaging. The camera and lens system has some limitations in terms of spatial resolution and contrast, as well as dealing with the effects of light bleed. You can see that the difference between the dark and light areas (contrast) is so great that the bright areas are washed out, and that adjacent pixels to the bright areas are washed out as well. So we'll have to wait for more resolved images to better guess at the nature of the bright areas - the data we need to determine the spatial variations, patters, and topography to better guess at the geology.

The latest close-up image at the higher resolution (bottom) seems consistent with some kind of geological process related to the heat-of-impact of "Occator" crater. Notice the spatial distribution and the patchy aspect of the varying surface albedo. The strongest source is dead-center, with eight or nine smaller point sources to the "NE" in a cluster that surrounds a weaker and patchier source zone. Now, think of a terrestrial analog of heat-driven surface alteration. The most familiar analog I can suggest are the hydrothermal features of Yellowstone, though there other more vapor-based, as in fumarole-based, analogs that don't involve as much water as Yellowstone's examples, which are more plausible analogs in the near-vacuum of Ceres, even if the impact produced a temporary tenuous atmosphere. One such example are the surface expressions at Casa Diablo (see my masters thesis). Imagine vapor generated at some depth below the surface rising up through the cracks of least resistance and forming deposits of ice and minerals, including the surface where the vapors escape to space is betrayed by the high albedo.


I see what looks like sand or dust dune type patterns on what looks like a dusty or sandy portion of the surface in the Oct. 18 image. Could solar winds acting on comet vent out-gassings cause enough flow across the surface of the comet to create sand or dust dunes? It might have happened during a previous passage near the Sun when things got really active. It's just an idea, but maybe not a completely unfounded one. For instance, Mars has a lot of different type dust dunes and related patterns across its surface and the atmospheric pressure there is a tiny fraction of the Earth's. Given the comet's exceptionally low gravity, it might not require much in the way of shear force imparted by a thin and temporary micro-atmosphere to do the trick.

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