I was wondering if the regular terraces are a result of seasonal or daily evaporative processes. If there was a catastrophic release of water could this be a daily boil freeze event record or seasonal record???http://www.msss.com/mars_images/moc/dec00_seds/8N7W/M14-01647subc1.jpg
John, No, the similarity between those terraces does not come from a repeated cycle of events. The terraces are similar because the layers were all created at the same time in a catastrophic impact surge flow.
I'm skeptical. Any terrestial parallels that you are aware of?
John, Its hard to know where to start, because I debated this topic on this site for months, mostly late last year. The best earth analogy is a wet base surge deposit: A mixture of liquid water and solid particles is explosively thrown horizontally away from a volcanic explosion. When the material stops moving it is often elegantly layered. On Mars, meteor impacts into the pulverized wet regolith are very likely to produce fluidised ejecta, a fact we know from looking at rampart craters. Huge impacts have happened over and over on Mars, but from reason, even though impact ejecta must be, by far, the most common sort of deposit on the planet, few seem willing to accept these ubiquitous layered deposits as ejecta. I do not think that there is much chance of convincing you of this either. Perhaps you will get interested and look into it yourself. It is just so much simpler an explanation than any other I have read, I will likely stay with it until strong evidence to the contrary appears. There is no other COMPLETE theory being offered, only tentative half-theories, usually involving complicated pre-conditions nothing like present-day Mars.
Really neat picture! I saw this explanation for polar terraces:
"Viking 2 spacecraft took this picture of the Martian north polar cap. The visible layering occurred as a result of wind born dust settling upon the polar cap. As the caps experience climatic variations, they expand and contract. The layers of dust sediment tend to grow thicker near the poles where ice deposits remain for longer periods of time. The thickness of the deposits indicates they were formed during cyclical climatic variation rather than annual changes. As ice withdraws from a region, wind exposes the layers sculpting valleys and scarps. The formation of layered deposits is an active process today."
So it's really a product of "mini ice ages". Currently, the south pole is warming up and the cap is eroding quickly (annual changes are observable). Not having a large moon to stablize it's rotation, Mars has a large precession.
Here's a nice description of climatic pole changes:
Although it appears the south pole has an even more complex formation process:
Marz, The polar layered deposits are a completely different phenomenon than the layered deposits visible all over the low and southern latitudes. The perennial polar caps are a mixture of water ice and dust, sometimes and in some places, covered by a thin layer of CO2 ice. One of the references that you linked in reply 4 suggests that the perennial south polar cap is mostly CO2 ice, but this has now been challenged.
Kyle, what thread should I look in for the debate?
Anonymous of Reply 6, A lot of that debate was in a thread called "Defining the Conditions for Spherule Growth", now buried deep in this Geology Section.
Have a look at the image linked in Aldo's Reply 61 top of page 4, and after that the "Brine Splat" debate appears here and there for many pages. Looking back at all that stuff makes me realize how hard it would be to follow a discussion through all this, because there are multiple topics on every thread. I still think that Meridiani and the Columbia Hills are impact surge deposits, though I have since become interested in other aspects of this mystery. If you get interested and have questions I will probably start to reiterate a lot of the evidence for impact surge as a source of layered deposits.
The terraces are regular, evenly spaced, mathamatical perfection. This screams of a CLYLICAL event. Further?
Anonymous of Reply 8, Yes many different cyclical series of events have been proposed to explain the regularly layered terrains. These have all been tentative, incomplete, complicated theories. The impact surge explanation is a simple, complete theory. Yes, it "connects" all those similar layers in a completely different way than all the other theories. Instead of a recording a repeated series of nearly identical events, the layers are all part of a single large event, an impact. The layering is not mathematically perfect, the layers are not perfectly evenly spaced. I think that they may turn out to be "single particle layers" like those that form in wet base surge and turbidity flow events on Earth and have also been identified in the Meridiani deposit. This may not be so, but in any case, I think that they record a fairly homogeneous part of a huge catastrophic event, not a series of similar events.
Kye, just wondering if you still adhere to your surge theory.
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