Anatomy of an alien IV: Sulfuria

Writing this a new post took a bit more time than usual, for which there are two reasons. The first is that quite often I simply run out of time. In fact, I have found that putting up a post almost every week (I did 50 in 2009) is about enough to stop me working on new content for the Furaha site. For that reason alone I may decide to slow down a bit.

The second reason is that I had lots of problems in trying to upload videos. The main reason was that I tried to do it with software I was unfamiliar with (Adobe Premiere Elements). I could make great titles with it, but the resulting file was about 850 Mb, whereas comparable earlier ones were less than 20 Mb. In the end I went back to the previous painful process involving three different programs and convoluted steps. There are too many video formats, and if you are not an expert life is hard.

Anyway, in the end I managed to upload a file. Today's post is once more about the BBC documentary 'Natural history of an alien', also known as 'Anatomy of an alien'. I rather prefer the first title. After that there will be only one fragment left to post on this blog, but this does not mean that the entire program will then have been posted here. Some parts deal with life on early Earth or on general biology, and I thought these would not be of major importance to the readership of this blog.

Both remaining sections feature the work of Dougal Dixon, someone who probably needs no introduction in the world of speculative biology. For those who do not know his work, he wrote several landmark books in the field, of which I like "After Man, a zoology of the future", and "The New Dinosaurs the best". In those years he and I communicated a few times by regular mail (yes, it was that long ago).

Click to enlarge; copyright BBC 1997

The present post is about the world 'Sulfuria', equiped with a very dense atmosphere. As discussed before, heavy atmospheres lend themselves well to flight, both of the 'heavier'and of the 'lighter-than-air' varieties. One of Sulfuria's major lifeforms is a 'ballont'; for previous discussions, see here, here and here. It is not a free floating one though, but a stalked one. The story is that these beings stick out above the clouds, where they are in the sun. Presumably sunlight is beneficial to them in the sense that it drives their biochemistry, but like many details in this programme the rationale for this is not spelled out.

The ballonts are rather nice, I think, but then again I have always been partials to ballonts. One small problem is that it is very difficult to get a sense of scale, if there is nothing in the image to compare the ballonts with. It would have been nice to learn a bit more about this biotope: there may be more flying forms, and some might be involved in the life cycle or ecology of he giant ballonts. I guess we will have to make these up ourselves.

The last fragment in this series will be posted in the near future, and will also deal with Dixon's work. In it, he discusses another invented world, called "Greenworld". I think I still have photocopies of sketches of Greenworld creatures he sent me years ago. Unfortunately, the work did not then see the light as a book, but I read recently that Greenworld is in fact about to be published, in Japanese. I will keep my eyes open for that one; not that I read Japanese, but I hope there will be pictures...

Anatomy of an alien III: Europan waters

The first blog entry in this new decade travels back in time again, to the 1997 BBC television series 'Anatomy of an alien'. This time the chosen fragment chosen deals with life on the moon Europa, or perhaps it may be better to call it 'in Europa', as the life forms in question are found in water underneath an ice cap over 15 km thick (according to the documentary).

You will first see an explanation of deep ocean vents on Earth, and those are never boring. Jack Cohen makes an appearance again, to speculate about similar vents in Europan seas or lakes. The vents are surrounded with walls built by bacteria that stretch upwards to form very long tubes. The speculation really gets underway when it deals with the ecosystem surrounding these tubes. There are creatures that can bite or drill through the wall of the tube, after which they gorge themselves on bacteria from within the tube. Of course there are predators out there too, preying on the 'grazers'.

Click to enlarge; copyright BBC

Here is a picture of a bacterivore; the predators have almost exactly the same shape. There is a feeding trunk on the front end of the animal, underneath the central opening. There is another opening in the front end of the animal; what is it for? Unfortunately, the documentary keeps completely silent about the body plan of these animals, which is a pity.

There is an opening right at the front, and one at the back. The one in the front is not for feeding. Perhaps these are the inlet and outlet openings of its respiratory system. After all, there is no reason to have air go in and out through the same opening, as is the case in Earth's tetrapods. Actually, using the same opening for air moving in and out is not good engineering, and is probably just a remnant of lungs starting as a sac with just one opening. In Earth's fish, waters enter the mouth and leave through its sides after having passed through the gills; a much better design! Obviously, evolution should be able to find other solutions on other worlds: air enters the lungs of Furahan hexapods through openings at the front of the trunk, and exits the body at its rear end (not that you can see that on any of the paintings on the site, but is true nevertheless).

Click to enlarge; copyright Gert van Dijk

Then again, the Europan bacteriovore's openings might have to do with propulsion, in which case these animals would have the same propulsion system as is found on Furaha. Just visit the page, choose the 'water' icon; choose 'swimming with...', and then got to the 'tubes' page. There you are. To save you the trouble I copied the image to this blog message; mind you, the image shows the external appearance of the animal; to understand how it works you still have to visit the page. I doubt that this propulsion system was separately invented for the Europan creatures. If so much thought would have gone into their design, you would think that this neat feature would be mentioned, and it isn't.

Still, there is something else about their propulsion that makes me wonder. The animals have a set of three fins around their body, more or less like the pectoral and back fins of sharks and dolphins. This makes sense, as three such fins are useful in countering rotations around the body's front-to-aft axis. You would want such fins near the centre of the body, as they would impede movements around the other axes if placed at the front or the rear of the animal. These animals indeed have three such wings right where you would expect them, around the centre of mass. As an aside, you may well wonder why there are three. To counter rotations, two or four (or more) would work just as well. Their area may have to increase if you have fewer fins, and vice versa, but that does not seem to be an important factor. Some whales have large dorsal fins and some have no dorsal fins at all, so having two seems to work as well as having three. Why are there never four? Is this just an evolutionary accident? Perhaps it is easier to have more such fins at the bottom half of the animal than at the top half, if only to make it easier to keep the body upright.

Anyway, now have a look at the tail of Europan bacterivores: there is another, smaller, set of three fins. That only makes sense if the animal needs more to be kept on track like an arrow, but this 'triad' fin design is not optimal if you use the tail for propulsion. Suppose you wish to beat the tail in an up and down direction: with a triad set the top fin will be useless for propulsion. While moving upwards it might even start to bend sideways and then it would impair propulsion. The other two will not be perpendicular to the direction of movement and will therefore not provide optimal thrust. No, if you want a beating tail, the surfaces providing propulsion must be perpendicular to the direction of the beat, and surfaces not aiding in propulsion should not be in the way.

Whale shark  / orca / orca; click to enlarge

The tails of sharks and whales provide excellent examples of this design. The pictures above were taken from the internet. The whale shark beats its tail sideways, and the 'stem' of the tail, just before the tail fin, is flattened sideways. In this way, there is room for the attachment of muscles and ligaments without impairing propulsion. The two photographs of orca's show that an orca's tail stem is flattened vertically, exactly as expected for an animal that beats its tail up and down.      
                  
Back to Europan bacterivores. Their tails suggest a mode of propulsion similar or identical to the ones I invented for Furaha. Convergent speculation once again? Possibly; remember that this type of propulsion results in linear motion without any externally visible means of propulsion. That is not what you see in the video. Instead, the predators near the end can be seen to swim with a strongly undulatory pattern, like the one you would expect for animals with sideways-beating tails.

I wonder what happened to cause this odd combination of a design plan with a movement pattern that doesn't seem to fit the plan. The people who designed these animals knew what they were doing, so the answer probably does not lie there. Perhaps the animators simply added a familiar type of movement to add some spice to the footage? That is possible: I remember from conversations with Steven Hanly that the movement of Eponan uthers in the same documentary did not come out as planned either. I doubt we will ever know.

 

"Anatomy of an alien": high gravity

A while ago, I showed a fragment of a 1997 BBC documentary called 'Anatomy of an Alien'. The fragment in question was about Epona, which was also what the post was about. The program contained discussions of more such extraterrestrial ideas, and contained short discussions with a variety of people involved in speculative biology, a term which I do not think had yet been introduced at the time.

Looking at the program makes you realise how fast computer graphics have evolved. Admittedly, the designers at the BBC probably did not have an enormous budget available, so they may not have been able to achieve the very best results technology could offer in 1997. In that period, 'Jurassic Park' was probably the yardstick you could get if you threw lots of money at the problem, and 'Jurassic park' dates from 1993. Still, the computer effects were certainly better than what an amateur could achieve.

I do not think that this means the program is no longer interesting to watch, so I decided to show some more fragments of the program. The one for today concerns life on high gravity planets. You will see an interview with Jack Cohen, a biologist with a strong interest in biology in science fiction. He has written a few books that all people who wish to design worlds should find interesting.  One I particularly recommend is 'Figments of reality'; a search on Amazon should result in several others.

In the video, Jack Cohen goes into the mechanics of legs for heavy worlds. He compares land-living crabs with sea-dwelling crabs to make the point that higher loads require stronger and more columnar legs, an effect encountered in this blog more than once. The resulting animation is quite nice. Another point that should be kept in mind is that high gravity is largely irrelevant under water. If your body mass is close to that of water, it will not take much effort to keep floating at the same height, and a relatively small swim bladder should allow you to change height at will. There's no risk of broken limbs from tripping under water.

On land, of course, things are quite different. In a truly high gravity the simplest trip could shatter your legs, so falling is something to be avoided at all cost. Even staying upright and walking requires legs that look different from those of animals of similar size on a low gravity planet (that's why I thought that Alex Ries' Birrin must live on a low-gravity world).

Click to enlarge (copyright BBC)

The video fragment shows a vaguely arthropod-looking animal, shown above, with a large number of vertically placed columnar legs. This makes excellent sense. The animal has large wings though, and that may seem surprising. Wouldn't high gravity make it more difficult to become airborne? It would, as a moment's thought reveals: staying aloft requires that weight, dragging an animal down, is exactly countered by the amount of lift pushing the animal upwards. If you double gravity and keep everything else the same, the situation is no longer in equilibrium, as weight is now twice as large as lift. Down you go.

But Jack Cohen makes the point in the video that high gravity may also make it easier to fly, by increasing the density of the air. It is indeed more easy to achieve lift in a soupy atmosphere than in a rarefied one, and vice versa. Disney's people knew that in 1957, as evidenced by the enormous wings of his Martian flying animals, designed to fly in the rare Martian atmosphere.

I checked some books and found that the amount of lift provided by wings is directly proportional to the density of the air. Here is the formula:

lift = 0.5 x density x wing area x velocity squared x lift coefficient

What that boils down to is that doubling the density of the air will double the amount of lift. That is nice: in the example above gravity was supposed to be twice as much as on Earth, so a doubling of lift is just what we need to keep the same animal in the air. Not that is at all likely that an animal living on a planet with twice the gravity and twice the air density could be the same as one living on a lighter world, but never mind that now.

So, to make things work, the only remaining question is whether doubling the gravity a terrestrial planet is compatible with doubling its air density. I have no idea. Comparing Venus and Earth suggests that similarly sized terrestrial planets can vary widely as far as their atmospheric density is concerned, so I guess a double air density is feasible. If anyone knows more about the relationships between gravity and likely atmospheric density of Earth-like planets, feel free to comment on this post.