OK kids we all should know by now that there is water in liquid form on mars. In aquifers, beneath the surface, the pressure is sufficient to prevent it boiling out into gaseous form.

It is a quite common for small amounts of water to "burp" to the surface on Mars. Mostly we see this in what appears to be mud flows (commonly in small craters). The water is pushed out, flows madly but briefly then quickly freezes up with a remainder boiling away.

In areas which are relatively free of the other ingredients which, with water make mud, we see the tubes. Are these typically adjacent to or set into protected rocky formations? Yes. Deep within the same process which burps water in other places causes a measured amount of water to push out here. The water has nothing to mix with and freezes quickly but not so quickly that it does not have time to form and hold into a "bubble" shape with the three "sides" forming walls. The process repeats at intervals, more measured amounts of water from the same source push and, because it is much warmer, thaws then defeats the original boundary of the ice allowing a second "bubble" to form. After a long enough time we see a series of water ice bubbles which look like glass tubes.

Take a close look at these tubes and note how they are each slightly different in shape and size. Do the math on pressure variances, surface to below grade in crevasses, make allowances for the changes in temperatures which correspond directly and find that it all makes sense. It is quite natural (on Mars).

OK now for the source of the burping. Easy. Gravitation influences from without. Study will reveal that the greatest activity of both types will be during a certain arc of proximity between Mars and her outward larger neighbors.

Sorry they are not glass tubes and they were not made by aliens unless those aliens were giant insects doing whatever it might be that a giant insect on mars might do.

JPS