29 May 2015

Tidal Locking, Flares and Photosynthesis on planets of Red Dwarfs (Geek Alert)

A short article about how the physics of atmospheres may act to prevent planets close to Red Dwarf stars from becoming tidally locked with respect to the star (like the Moon to the Earth or most of the giant planets' satellites with respect to them) (From Physicsworld):
(Link below)

This is all well and good, and I understand, of course, the interest in discovering any circumstances which may make the existence of habitable planets in M-V class (Red Dwarf) systems (which, after all, are something like 80% of all star systems) more likely.
However, an even bigger problem for the existence of habitable planets in such systems is the prevalence of powerful, and really quite lethal, stellar flares. You see, the following facts are well established:
  • 1. Solar (stellar) flares occur in approximately the same dimensions and power on medium to large size main sequence stars or on small, dwarf type stars. Proportionally, a flare may only be 1% increase in brightness on a G type main sequence star, but a similar flare, on a red dwarf, might briefly increase the star's brightness (and lethal hard radiation output) by 50% or even more.
  • 2. The habitable zone of such small stars is very close; within a few million miles, where proximity to such flares would be almost certainly lethal to any complex life residing on the surface of any planets located in those zones.
  • 3. Class M stars tend to have such flares quite frequently; in fact one group of such stars is referred to as "flare stars" because they occur as frequently as every few days.
The inescapable conclusion is that 80% of the stars, those in the M class, are probably ruled out for habitable worlds because of flares alone, regardless of whether they are rotationally stopped.
HOWEVER, one thing is sure. Humanity's investigations into these issues is in its infancy, and we really do not know the answers to these questions yet.

I will leave aside the issue that the wavelength of light from such stars is believed to be insufficient, on pure physics principles, for effective photosynthesis by organisms, although of course that is hardly encouraging either. The authors of the book «Revolutions that Made the Earth» (Lenton & Watson, Oxford 2010) were quite adamant that the photosynthesis reactions simply do not occur in with photons where the peak radiation is in the far red, which is what you have there, and that even tweaking the chemistry would probably not work because the problem is the energy of the each photon it takes to break a water molecule bond, which is higher than the energy of the red photons at issue. (If the energy of the photons isn't high enough, no matter what the flux of photons is, the reactions just don't take place). No substitution of alternative chemistry can change that fundamental physical parameter. I also leave to the side the tacit assumption that oxygenating (water-molecule breaking) photosynthesis, which evolved on Earth only the one time (the evolution of cyanobacteria, the common ancestor of ALL terrestrial oxygenic photosynthesizers), is absolutely necessary for the evolution of complex life, although I do believe that case is very, very strong.

28 May 2015

Bird Breath

Here's something every schoolkid should know, but very few people have ever even heard about. Despite centuries of study of bird anatomy, it was only really figured out in 2005! Read about it in Ward and Kirshvink, A New History of Life, which I recommend.

Birds (which are, for all practical purposes, saurischian dinosaurs whose last common ancestor with us was about 200 million plus years back) have a vastly superior respiratory system to that of mammals or other (extinct) dinosaurs. Their tracheas go all the way to where our diaphragm would be, and they have air sacs, which fill with air when they breathe. They then push the air through their lungs and out. So it's all one way flow, far more efficient than our in and out breathing. It was originally an adaptation to the low oxygen world of the early Triassic. It enables them to breathe independently of locomotion (mammals have to coordinate their breathing), use less energy to breathe, and survive on lower oxygen levels.

The homologous bones in saurischian dinosaur fossils prove that they too had this system.

Now, I bet you didn't know THAT.

23 May 2015

Interesting developments in thinking about the History of Life on Earth

I should like to briefly share with you some very interesting points made by Ward and Kirshvink in New History of Life.

First, they take very seriously the idea that life might have originated on Mars and been transported to Earth sometime after the Late Bombardment, roughly -3.8 GA. They explain that one of the most “difficult” processes in the origin of life was the synthesis of ribose (essential to the theory of the origin of life), and consequently of RNA and later DNA. These substances cannot have spontaneously arisen in water. But the Earth of that era was almost certainly entirely covered by oceans, with no land surface at all (there was about four times as much water as at present, and the continental crusts had not yet differentiated). So where did the ribose come from?

Experiments have shown that ribose can self-synthesize in the presence of boron salts, which can arise as a result of chained evaporitic lakes in severe deserts. The best contemporary example is the deserts of the Amargosa watershed (Death Valley). But it is quite plausible that something like this could have occurred in impact crater lakes on Mars of this era. Mars is believed to have had a thicker atmosphere and seas and lakes at that time, but to have been mostly rather severe desert.

Couple this with the fact that over 1 billion tonnes of material has found its way as the result of meteorite strikes to Mars, from Mars to Earth, since that era. It thus becomes quite plausible to suppose that ribose and “RNA world” life could have evolved on Mars, where, as a result of desiccation and UV sterilization it subsequently became extinct. But not before “contaminating” the previously sterile Earth with … life!

Another issue they discuss in some depth is the near-complete abandonment of the former paradigm of uniformitarianism. It is now pretty well established that there were at least two, and possibly as many as four, planetwide “Snowball Earth” glaciations, each of which lasted tens of millions of years, before the eventual emergence of “complex life” in the latest Proterozoic, setting the stage for the “Cambrian explosion.”

As they explain (the reasoning based on chemistry is complex), it is highly likely that the first, and in fact only  time oxygen producing photosynthesis ever evolved (the emergence of cyanobacteria) occurred just prior to, and in fact triggered, the first of these Snowball Earth episodes (water-breaking photosynthesis drew down previously high levels of greenhouse gases methane and CO-2). The emergence of an oxygen rich atmosphere depended on these “catastrophes,” as did the emergence of complex life and probably even of nucleated cells (Eukarya). This is completely contrary to former views that evolution of photosynthesizing life, then nucleated cells, then complex, multicellular life, was all a smooth process of increasing complexification.

Previously, it was always assumed that “Snowballs” could not have happened, because if the Earth ever had surface ice all the way to the equator, because of ice albedo effect, that condition would be permanent ---at least until the ever-brightening sun finally melted the ice, in around 1 GA from now, although by then it would be too late for complex life to evolve, since the melting of the ice would be followed almost immediately by the complete loss of the oceans to space; which is what will happen around that time in any case. If a “Snowball” were to occur in the future, in fact, that is what would happen, because volcanism has declined over time and there would be no effective mechanism for melting the ice. (Indeed, until the 1970s even the fact that, as a typical main sequence star, the Sun has been brightening continuously throughout its life and will continue to do so was scarcely appreciated, and the effects it had on the evolution of habitability on our planet was not thoroughly analyszed or understood. This fact, and its implications, are not well known to most educated people even today).

It is now understood that the ancient Snowballs eventually came to an end because there was nothing to remove CO-2 from the atmosphere, so it built up, from volcanic release, primarily. Indeed, CO-2 levels may well have reached 15% or even higher, before finally reaching a high enough level to increase air temperatures sufficiently to cause the ice to melt. But with such high levels of CO-2, the Earth’s climate shifted suddenly to ultra-Greenhouse, and temperatures reached extreme levels. Only when the deposition of carbonate rock (which reached maxima in these post-Snowball eras) finally brought CO-2 levels down, did the climate stabilize. The whole process was a close call, however. Had the Earth been only a little further from the Sun, it’s believed that the temperature at the poles during Snowball episodes would have been below the freezing point for dry ice. Had that occurred, the CO-2 from the volcanism would have precipitated at the poles, and the Earth would indeed have remained ice-covered until the brightening sun finally melted the ice, some 1 GA from now.

All of this shows that previous uniformitarian models are clearly wrong, and a form of pre-Lyellian catastrophism is actually closer to the truth. It also supports a growing consensus that the complex life of our planet is the result of quite a series of relatively unlikely evolutionary and geo-system events, some of which life barely managed to squeak past, including the origin of RNA (which may have depended on importation of life itself from Mars!), the evolution of oxygen-producing photosynthesis, which happened only one time and in the context of global environmental catastrophe, and the origin of endosymbiotic nucleated cells, which also apparently only happened one time.

Heady stuff.

21 May 2015

Fast Track Rammed through Elitist Senate

I deplore what the old boy's club known as the Senate has done... ramming through Fast Track Approval for the TPP and other trade deals negotiated in secret and without adequate safeguards to ensure that they are compatible with our representative form of government. This is a very, very bad development for the interests of ordinary working people, and a very good one for the interests of the largest corporations and richest Americans. Why Democratic senators or representatives or this president, think this is going to be acceptable to rank and file members of the Democratic Party, I cannot say. Because it is not acceptable to me and I will not be voting for any of them when they present for re-election, nor for any candidate seeking the presidential nomination who supports this travesty of democracy.

20 May 2015

Reid opposing Fast Track Authority

I'm glad to see Harry Reid standing against the very unwise cession of Congressional authority over trade treaties (no matter what they're called, Rand Paul is right (for once) that these are actually treaties and should be subject to Constitutional constraints on treaty powers). On this issue, as I've been saying, I'm convinced that President Obama is just wrong, and I note that he has completely failed to make a substantive and coherent case for his position to the American people.

See this