24 October 2010

The Tubes of Mars

Posted by Ryan Anderson

Last week was my birthday, and I unexpectedly got a gift in the mail from my cousin. We don’t normally exchange birthday gifts, but she came across a t-shirt called “Tubes of Mars” and just had to buy it for me. Apparently, this line of shirts is capitalizing on various wacky conspiracy theories and they decided to use one of my favorites, the “glass tubes on Mars” idea.

The shirt itself has a swirly-looking abstract design on it, but then down in the corner it has a caption in fine print explaining:

Photographs taken from Martian orbit reveal what appear to be miles and miles of ribbed ‘tubes’ on the surface of the red planet. It is estimated that these tubes have diameters of close to 600 feet. Some have tried to explain these formations as a the result of geological processes. Others believe they are organic in nature. Yet some are convinced the tubes may have been constructed.

If you’re not familiar with this hoax, let me explain, starting with a picture.

Here's a HiRISE view of some channels on Mars full of aeolian ripples.

See the numerous light-toned ridges arrayed along that canyon floor? There is a group of people who claim that these features are actually the support struts of transparent tubes that crisscross the martian surface. I’ll grant that if you have no idea what you’re looking at, these things might sort of look like a tube of some sort, but it’s actually an illusion. The light-toned ridges are ripples of wind-blown material, likely coarse sand or gravel. These are seen all over the place on Mars, and they don’t always look so tubular. Heck, the Opportunity rover has been driving across ripples like these for years! The thing that is confusing people is that these ripples are extremely common in canyons, and because the canyons funnel the surface winds so that they blow down the length of the trough, the ripples are oriented perpendicular to the canyon walls. If you look closely you can see that these are clearly wind-blown ripples. Take this HiRISE image for example:

Here's a HiRISE view of some channels on Mars full of aeolian ripples.

The channels in this image are filled with aeolian ripples. If you were really determined to see a tube, I suppose you could at the scale shown above, but if we zoom in even more that explanation disintegrates:

You can see here that the larger ripples break up into more complicated ripples toward the edges, and that there is a secondary wind direction forming small ripples perpendicular to the big ones.

I’ve always found the belief that these features are some sort of glass tubes on Mars to be both funny and sad at the same time. It shows a complete lack of understanding of the very interesting geology at work on Mars (and Earth), along with a somewhat disturbing willingness to see evidence of outlandish claims and conspiracies everywhere. Those of us in Mars science are all too familiar with this. There’s a long tradition of seeing what you want to see on Mars, going all the way back to the famous “canals”. These days, no scientists really think there’s macroscopic evidence of life on Mars, but I think there is still a very strong desire among scientists and the public for early Mars to have been “warm and wet” (a.k.a. Earth-like). Maybe it really was earth-like, but maybe it wasn’t. We all need to be vigilant and make sure the way we want Mars to be doesn’t cloud our conclusions.