I become highly annoyed at times with the back and forth from both sides of this debate: the jpl/nasa view that these things are merely dune trains, and the everything-from-psychically-predicted-transportation-tubes-of-a-vast-Martian-civilization-to-giant-Mars-worms crowd. Someone in this thread has denounced Mr. Arthur C. Clarke as merely a science fiction writer. Face it, any speculation about the nature of these things is science fiction at this juncture, arrogance and certitude on both sides notwithstanding.
So what do we actually know about these things? For one, they seem to exhibit features that impresses some viewers as artificial, some as organic, and some as completely natural, in a geologic sense. We know that for a fact, and we know that divergence of impression leads to argument. We also know, who have read these postings over the years, that there are drawbacks to each of these opinions.
Fact: We don't really, any of us on this earth, know what the hell those things are, but they strike virtually everyone who sees them as anomalous, intriguing, strange, outside of our experience.
Fact: The possibility exists that they are entirely natural, and the lack of anything like them on earth does not establish a sound predictive base for Martian geology.
Fact: The possibility exists that they have been made by something living, at some point in Martian history.
Fact: They bear further investigation in detail, by orbiters, by landers, and by astronauts, should the day ever come, until we can determine, once and for all, their nature. Until that is done, all argument is futile, though I don't expect it to cease, not for one minute.

• ice - blackdeep - February 22, 2005 - 06:04 UTC