Nickel and timed

One of the problems with studying the origin and evolution of life is that our mother Earth has a shady memory.  The farther back in time we go, the rarer and more fragmented the rock record becomes. What this basically means is that for most of the first third of Earth’s history, we run out of rock record before we get back far enough it time to discover the origin of various fundamental early steps in our own evolution. Even for more recent developments, like the oxygenation of the atmosphere and the recent great extinction events, the rock record is frustratingly incomplete. This has several effects.

On the observational side, it requires scientists to draw bigger and bigger conclusions from slimmer and slimmer data. Was there life in the Hadean? If all you have is a pinhead pile of ground up zircons, there is only so much evidence you can put forth.

On the theoretical side, there is of course even more speculation and unconstrained hypothesizing. With older rocks more common on smaller, deader worlds, and hypotheses like Panspermia positing that space is no barrier to the spread of life, there is literally a universe of possibilities. As a result, many theorists have lapsed into quasimystical approaches to the framework for how life has evolved from very early primitive micro-organisms to space age simians who none-the-less waste their time reading this blog. The approaches generally fall into two broad categories.

The first is the “Manifest Destiny” approach. This school of though believes that life is an unstoppable, inexorable force that will climb every mountain, contaminate every spacecraft, and spread in an inexorable evolving wave throughout the universe. Most astrobiologists subscribe to this belief, as it is easier to justify your life’s work if you think that there is actually something out there to find.

The second is the “There but for the Grace of God” approach, which envisages life as a blind, reactive encrustation to grand events and processes far beyond its control. Proponents tend to be hard rock geologists and extinction researchers.

It is important to note that these are hypothetical endmembers- most researchers lie on a solid solution between them, albeit generally closer to one end than the other. It is also important to note that although I have deliberately used non-scientific labels, as these leanings are often manifestations of inclination rather than deduction, an inclination towards one camp or another is in no way an indication that a particular research is not a great scientist. Rather, it is an attempt to colorfully illustrate two diametric approaches taken to thinking about the early history of life.

Tonight, however, I’d like to draw attention to a paper that combines these approaches in a fascinating way. Konhauser et al. 2007 posit an Archean Earth where Nickel-dependent methanogens had evolved to become the dominant life form on the planet. The oxygenation of the Earth’s atmosphere was not a result of oxidative photosynthesis evolving and outcompeting the methanogens. Rather, the decrease in high-temperature, nickel-rich komatiitic volcanism at the end of the Archean weakened the methanogens by creating a shortage of the nickel they needed to survive, reducing methane production and allowing oxygen producers to take over.

            Scientifically, this idea is appealing because increasing lines of evidence, such as that summarized in Geosonnet 21, indicate that oxygen production was going on long before the great oxygenation at a limited local level. But for hundreds of millions of years, it was never more than a transient, small scale local phenomenon.  This hypothesis is also nice in that it ties the large scale tectonic and igneous changes between the Archean and the Proterozoic with the change in atmosphere. Linking those two fundamental shifts in the Earth’s history is always nice, as having them coincidentally synchronous seems somewhat implausible.

            On a purely personal level, however, the proposed narrative reminds me of the H. P. Lovecraft novel, “At the Mountains of Madness” The difference is that the Archean overlords who ruled the hostile ancient Earth were not 3 meters tall. They were 3 microns tall instead. And it was mantle convection, not decadence in intergalactic civilizations, that allowed our distant aerobic forbearers to liberate their planet.

2011 Arctic sea ice extent minimum prediction pool

Update:
The contest so far:


Neven and Peter are reminded that contestants who have been mathematically eliminated at the 2 sigma level are entitled to guess again. It is up to you guys to keep track, though. This post will remain on top until the contest closes.

original post:

The 2011 Arctic sea ice extent minimum prediction pool is now open. A reminder that this is a competition on extent, not coverage.

The 2010 summed guess curve and final result are shown below:


Guesses are to be in the form of extent and sigma (a mathematical measure of uncertainty), in thousands of km² You may use decimal places if you insist.

Your guess will define a Gaussian curve.

The function with the highest value for x=minimum daily measured ice extent (from IARC-JAXA) wins.

See the 2009 announcement, opening, and final curve for details.

This contest will close much sooner than last year's. Guesses must be submitted by the time the Earth reaches aphelion in its orbit, which the internet tells me is 3 pm on July 4 (UTC). Trash talking, dissembling, and boasting in the comments section is still encouraged.

The prize, as always, is the choice of a blog topic on which I will write.

Taking the niggers out of Huck Finn

At the beginning of this year, there was an internet brouhaha over the politically correct decision to replace all instances of the word “nigger” with "slave" in a forthcoming edition of the American classic novel, “The Adventures of Huckleberry Finn”. I have been vehemently opposed to political correctness ever since I was told at college orientation that exercising my first amendment rights was grounds for dismissal from university. So when I read about this controversy, I chose to react in the most politically incorrect manner possible: I decided to take the time to re-read the book instead of spouting off instantly and emotionally. Six months later, the internet has long since forgotten about this event, and I’m finally ready to comment.

Being politically incorrect, my first reaction was that, if they were going to start substituting words, they ought to be adding slurs, not removing them. For example, the text of Huck Finn contains 51 instances of “white”. What if we were to replace all these with “trailer trash”?

The answer, of course, is that the story starts to make less sense. For example, consider the introduction of Huck’s father:

There warn't no color in his face, where his face showed; it was trailer trash; not like another man's trailer trash, but a trailer trash to make a body sick, a trailer trash to make a body's flesh crawl -- a tree-toad trailer trash, a fish-belly trailer trash.

Since more than three quarters of the instances of “white” in the story do not refer to race, it requires a bit of picking and choosing to get this substitution to work:

And here comes the trailer trash woman running from the house, about forty-five or fifty year old, bareheaded, and her spinning-stick in her hand; and behind her comes her little trailer trash children, acting the same way the little niggers was going.

Of course, trailers are an anachronism, and as far as epithets go, “trailer trash” is about as mild as they get: the only people likely to be offended by it probably haven’t discovered the internet yet. And it isn't even politically incorrect, since the only people it is politically correct to slur are the uneducated rural whites. So let’s try something else.

One obvious use of politically uncorrect substitution is to determine whether words are being used derogatorily. For example, if "lady" is used in a class warfare, resentful, or sarcastic context, then substituting a politically incorrect derogatory synonym (of which there are many) should preserve the tone of the passage. Performing the substitution allows us to test this hypothesis, which the very first of the 12 substitutions finds wanting:

Three big men with guns pointed at me, which made me wince, I tell you; the oldest, gray and about sixty, the other two thirty or more -- all of them fine and handsome -- and the sweetest old gray-headed cunt, and back of her two young women which I couldn't see right well.

Rachel Grangerford (the grey-haired lady/cunt) is depicted as a sympathetic, motherly character. Even in outback Australian trucking circles, where every fourth word is cunt, the above passage would be incongruous. She is the subject of five of the first seven instances of ‘lady’, and the other two refer wistfully to drawings made by Emmeline Grangerford, another sympathetic character. Most of the rest of the uses of ‘lady’ refer to fine-looking circus performers, who are not viewed particularly badly.

In fact, there are relatively few horrible female characters in Huck Finn. The least sympathetic would probably be Miss Watson, the evangelizing sister of Huck’s legal guardian who tries to sell Jim downriver. The following passage retains most of its original meaning, for example:

I noticed dey wuz a nigger trader roun' de place considable lately, en I begin to git oneasy. Well, one night I creeps to de do' pooty late, en de do' warn't quite shet, en I hear de old cunt tell de widder she gwyne to sell me down to Orleans, but she didn' want to, but she could git eight hund'd dollars for me, en it 'uz sich a big stack o' money she couldn' resis'. De widder she try to git her to say she wouldn' do it, but I never waited to hear de res'. I lit out mighty quick, I tell you.

Of course, one has to be careful doing an automatic search and replace of all 110 instances of “miss”. Firstly, cunt is not a verb, and secondly, the story is set on the Missouri bank of the Mississippi river.

But I digress. The uproar about this book is not the cunts. It is the niggers. And if the politically correct way of addressing this is to turn all instances of nigger to slave, then the politically anticorrect response should be to change all the original uses of the word slave to nigger. And this is where things get interesting.

Despite the word nigger appearing in the text 212 times, slave only appears 11. Five of those are in “slavery”, and another refers to “slave country”. The remaining five are related to Jim’s sale to the Phelps family by the King, Huck stealing him, and the news that Miss Watson freed Jim in her will on account of feeling bad about trying to sell him.

The word slave is only used to specifically refer to the condition of someone (usually Jim) being owned. It is not used to refer to people as human beings. In the original text, it is simply not interchangeable with nigger, or black, or any other reference to people, African-American or otherwise.

Slavery is an institution that quite literally reduces people to mere property- it is the ultimate form of objectification. So the original texts refusal to label the people subjected to this institution with the word slave is probably important, given that the author had hundreds of chances to do so. In this way, the text condemns the institution in a way that would be lost in the politically correct rewording.

Of course, "The Adventures of Huckleberry Finn" is not the only form of literature to have been deniggered. For example, the well known nursery school rhyme:

Eeny, meeny, miny, moe,
Catch a nigger by the toe.
If it hollers let him go,
Eeny, meeny, miny, moe

Has been edited to replace nigger with tiger. To the best of my knowledge, this did not precipitate howls of outrage among the self-appointed internet literati. However, such a substitution might be a bit awkward for Huck Finn:

Tigers would come miles to hear Jim tell about it, and he was more looked up to than any tiger in that country. Strange tigers would stand with their mouths open and look him all over, same as if he was a wonder. Tigers is always talking about witches in the dark by the kitchen fire; but whenever one was talking and letting on to know all about such things, Jim would happen in and say, "Hm! What you know 'bout witches?" and that tiger was corked up and had to take a back seat. Jim always kept that five-center piece round his neck with a string, and said it was a charm the devil give to him with his own hands, and told him he could cure anybody with it and fetch witches whenever he wanted to just by saying something to it; but he never told what it was he said to it. Tigers would come from all around there and give Jim anything they had, just for a sight of that five-center piece; but they wouldn't touch it, because the devil had had his hands on it.

It may be that politically correct readers wish to substitute something other than slave or tiger throughout this novel; feel free to leave suggestions, with examples of replaced text, in comments.

A more general point is that experimental search and replace is an interesting tool of textural analysis. Obviously it can only be used in the case of works available in an editable format, which for practical purposes means the public domain. But it shows that the traditional scientific methods of exploring a system by changing one variable at a time can be applied to literature. There has be much in the news of late about the controversial practice of statistically mining literature. So experimentation is the next obvious step in the sciencification of literary analysis.

Systematically changing the language of various masterpieces is a useful analytical tool. But I suspect that anti-science traditionalists will see this technique as blasphemous vandalism which is even more offensive than the derogatory words used freely in this post.

Testing the earthquake-modesty connection

The blogosphere is abuzz with the news that an Iranian cleric has recently hypothesized that immodest dress causes earthquakes. One aspect of this proclamation has been ignored by the commentariat, however. As a scientific hypothesis, this prediction is very well formulated. More so, in fact, than many of the statements made by professional scientists.

The reason that it is well formulkated is simple: As stated, the hypothesis is easily tested. Furthermore, it can be tested via a variety of independent methods, thus reducing the possibility that selection or methodological bias is clouding the results. Professor Jefferson over at Highly Allochthonous has already described one experimental method of verifying the cleric’s statements, the results of which will hopefully be revealed later this week. But because of the sweeping nature of the statement, historical data should also be able to be mined to determine its accuracy.


The USGS maps the earthquake density for the entire world.

Using this map, we should be able to predict the relative modesty of various parts of the planet. One would expect more quakes in immodest places. A close look at the Mediterranean region shows that the Eastern Mediterranean (from Italy East) has a higher earthquake density than the Western Mediterranean; similarly, the north coast has more quakes than the south. Thus, we would expect the attire in somewhere like Lebanon to be less modest than, say, Morrocco. Thanks to the wonders of the internet, we can instantly acquire completely unbiased and accurate data relating to this subject simply by doing a Google image seach of “X beach” where X is either Lebanon or Morocco. And here are the results:

A Lebanon beach:


A Moroccan beach:


These results are broadly in line with the cleric’s prediction; the dress on the Moroccan beach is substantially more modest than that found in Lebanon. So the Iranians might be right about this.

However, a central tenet of science is that results should be repeatable; repeating this test for other regions should yield similar results most of the time. So let us try again.

Looking at the world map outside of the Mediterranean region, one of the largest earthquake-free continental areas is Brazil, in eastern South America. Therefore, we would expect Brazilians to have the planet’s most modest clothing. If we contrast their attire to that worn in an earthquake-prone region, such as the cleric’s native Iran, we should be able to confirm his beliefs.
Brazilian beachware generally looks like this:

And already, you can see that we have a problem. In theory, this should be less revealing than both Morocco and Lebanon, but that’s not what I’m picking up here. Still, if the swimwear of Iran is very, very revealing, then there may be a point to be had.

So let’s have a look.

Pardon the frequent carriage returns.

However,

If this next picture is as...

Immodest as the clerics predict,

Then,

It is probably a good idea to keep the reader’s hand on their computer controls, if you know what I mean.

So without further delay,

The infallible Google image seach informs us that

An Iranian beach looks like this:

Oh dear.

I see only two possible explanations. The first is that the clerics are wrong, and immodesty has nothing to do with earthquakes. However, there is another possibility.

If God is from New Zealand, then the Iranian picture is far more risqué than the Brazilian one (by traditional New Zealand standards), and the hypothesis is still intact.

I don’t believe the cyber commentariat has considered this possibility. Thus further analysis is required, and I encourage all of you to search for location-specific images of scanty attire. After all, this is why the internet was invented. If anyone asks why you have twenty browser windows full of bikinis, tell them it's for science.

But where are the sharks?

A recent radio news segment I heard was fearmongering on a laser technology that, if deployed, could potentially destroy us all in the coming nuclear apocalypse. I found a writeup here.

The idea is this: a few decades back, Some Australian researchers developed a technology to perform isotopic separation on uranium using lasers. Uranium has 2 main isotopes, ²³⁵U and ²³⁸U. ²³⁵U has a short (706 million years) half-life, while the half-life of ²³⁸U is about the age of the Earth. As a result, the Earth still has ½ of its original ²³⁸U supply, while about 63 64ths of the initial ²³⁵U has decayed. As a result, modern U has a very high ²³⁸U/²³⁵U ratio: 138:1.

It is the less abundant isotope- ²³⁵U- that undergoes neutron-induced fission in nuclear power plants, research reactors, and atom bombs. And the ²³⁸U gets in the way. So before uranium can be induced to fission, some of the ²³⁸U has to be removed. The remaining uranium after most of the ²³⁸U is removed is ENRICHED uranium. The level of enrichment depends on the purpose for which the uranium is to be used, and can result in a ²³⁸U/²³⁵U ratio of anything from 50 (low enrichment) to 0.1 (weapons grade).

The 2²³⁸U-rich uranium removed from the process is known as DEPLETED uranium, and generally has a ²³⁸U/²³⁵U ratio of about 400-500, depending on the particular source (I have a funny story about measuring this by accident- maybe some later post).

Separating isotopes requires a lot of energy- so much that it is a significant source of inefficiency in nuclear power, and one of the main technological hurdles involved in making a nuclear weapon. All the concern about Iran at the moment is related to their uranium enrichment process, for example, because election stealing, mistreatment of women, and generally thuggery are comparatively minor offences.

The big deal with laser-excitation isotope separation is that it is more efficient than previous methods. So if you have a clandestine nuclear weapons program, you can use much smaller factories, which are harder to detect. Or, if you are trying to stop global warming, you can make nuclear power generation more efficient. So the consequences of the technology depend greatly on the motives of the people deploying it.

Because of the potential negative consequences, the technology was transferred from the Australian university lab where it was developed to the US government back in the 90’s. And they classified it, so I can’t tell you the details of how it works. Especially not the details of attaching the lasers to the sharks.

The reason it has come up now is that a laser separation plant has been proposed for North Carolina. As far as I know, there are no plans for a tarheel bomb. While NC did fight the United States during the civil war, there is little evidence that the state wants to resume the conflict. They’re even considering ignoring that part of history. Unlike South Carolina, they know the war is over, and even voted for the black liberal guy in the last presidential election. So unless you’re a fanatical kosher evangelist who finds the world’s best BBQ pork to be an international outrage, North Carolina is not a rogue state.

In fact, the critics of this planned laser separation technique don’t even explain how they expect proliferation to happen. It is just a vague sentiment that if this particular nuclear technology works, it will somehow spread to the hands of the bad guys.

I don’t buy this, for the following reason. The technology has already been discovered- it is 12 years old. So rogue operators have had all that time to figure it out. Stopping a peaceful application will not prevent the bad guys from building their own systems using the theory. Building a peaceful system is only a risk if the technology from that system is then sold to the bad guys. And I don’t really see GE putting their surplus lasers on craiglist Tehran. GE makes entire reactors, and if they were in the proliferation business, they already have plenty of other ways of giving out nuclear technology.

In short, there is nothing specific about this laser system that makes it particularly likely to proliferate, so the arguments against it are general anti-nuclear efficiency arguments. So this is hardly the nightmare scenario that it was hyped up to be.

In a way, this is disappointing. I can think of some bona-fide nightmare isotope separation proliferation scenarios, and this is nowhere near what I would call worrying.

For example, geochemists often measure natural changes in isotopic ratios because these changes can tell us about various geologic or biologic processes. In generally heavy elements like U naturally separate less than light isotopes like H. But under ideal conditions, heavy isotopes can fractionate (“fractionate” is the word for natural separation). And one of the most powerful natural fractionation methods is biological activity. Photosynthesis causes most of the biosphere’s carbon isotopic fractionation, for example, and biologic fractionation has been documented in elements as heavy as Hg. So a real, bona-fine nightmare separation technology would involve not lasers, but microbes. A uranium-fractionating bacterium or yeast would be far, far more threatening than laser technology or any other technologically sophisticated system.

Unlike lasers, microbes breed. And they don’t use electricity, they just eat. So instead of needing a factory to separate isotopes, you could use a bottle. Every tub of yoghurt, every vat of beer would be a potential weapons lab. Tzatziki and chaca would become proliferation risks. And fermentation extracts such as vegemite would be proscribed as the planet’s most terrifying "V-bomb" precursors.

In short, learning that yeast had been weaponized, or that landfill methanogens were accumulating a critical mass under Fresh Kills or Woodlawn would be a nightmare scenario. This laser stuff? Bush league material for Bond Villain wannabes.

Stars get lonely too

In the field of exoplanetary detection and characterization, relatively little work has been done on the mental health of the stars in our sector of the galaxy. However, a new paper by Israelian et al. has begun to change that. Their study shows that stars without planetary companions contain as much as ten times as much lithium as the sun.

Lithium, of course, is an antidepressant. Unlike molecular antidepressants like Prozac, it is stable at the temperatures found in the upper layers of luminous stars. Over time, this lithium mixes into the core of the star, where it is destroyed. So the observation that 50% of stars without planets have high levels of lithium suggests that they have been having lithium added via an external source, such as medication.

The obvious conclusion is that these isolated stars have a higher incidence of mental health problems. Lithium is commonly used to treat depression and bipolar disorder, and these diseases may be more common in stars isolated in the vast loneliness of intergalactic space without the companionship of planets. If this hypothesis is correct, then we would expect none of the high-lithium, medicated stars to exhibit variable luminosity associated with bipolar disorders.

Note: I couldn’t find this paper in the arxiv, and Nature only allows access to the abstract by the public. I read that, but I cannot rule out the possibility that I have misinterpreted the research as a result of their access policy.

Party like the Paleoproterozoic

The Paleoproterozoic was an interesting time. Oxygen finally settled into the atmosphere on a permanent basis, most of the iron formations we use to make cars, bridges, skyscrapers etc. were formed, and the removal of methane from the atmosphere cooled the surface until everything froze, creating a condition known as the “snowball Earth”.

Similar conditions may have reoccurred again in the Neoproterozoic, but since then, the tropics have tended towards being ice free. But will this last? A simple extrapolation says no.


Figure 1. linear extrapolation of the last three years of sea ice minima.

As you can see, sea ice has been increasing for the last three years, by about half a million km ^2 per year. With only 360 million km^2 of ocean on the planet, a continuation of this trend will freeze the entire ocean by the year 2724! We are all doomed.

33S

33-Sulphur, the colloquial name for the atom with 16 protons and 17 neutrons in its nucleus, is one of science’s more interesting characters. Many elements have multiple isotopes. Sulphur, for example, has four (mass 32,33,34,36). And while isotopes are chemically similar to each other, they can be separated to some degree in biological of physical systems. These effects produce what is called mass-dependent fractionation, where the degree of enrichment (or depletion) of the various isotopes is a function of their mass.

Mass dependent fractionation of various isotopes is used for everything from making nuclear bombs to predicting the mass of ice-age glaciers. In the case of Sulphur, it is generally measured by comparing the ratio of ³²S (the most abundant isotope) to ³⁴S (the second most abundant). Calculations show that the fractionation of ³³S from ³²S should be about half of the fractionation of ³⁴S from ³²S. Since ³³S is about 8 times less abundant, and the signal is expected to be half the size, measuring it seems like a silly think to do.

That all changed in 2000 when Farquhar et al. showed that Archean sulphides showed a ³³S anomaly that was not consistent with mass-dependent fractionation. This anomaly is expressed as Δ³³S, the difference between the expected value (based on extrapolation from the measured ³⁴S/³²S ratio, and the measured ³³S/³²S ratio, and is generally only present in archean sedimentary rocks.

One of the few processes that produces mass-independent fractionation (MIF) is photolysis of sulphurous gasses by UV radiation (the exact mechanism is still being researched). So the presence of these anomalous ratios in early sediments is generally thought to be an indicator that there was no ozone or other UV-blocking layer in the atmosphere at that time, and there were enough atmospheric suphur-bearing compounds to be dissociated by that radiation.

In 2003 Mojzsis et al. did some classy ion probe work (using a non-SHRIMP instrument) on in-situ sulphide grains so show where in the rock the anomalous D³³S was located. Our approach was somewhat different.

My hypothesis was that the Monica Lewinsky scandal of the late 1990’s caused enough hyperventilation to such all the oxygen out of the atmosphere and return the surface conditions of Earth to those of the late Archean. So I chose to test this hypothesis my analyzing sulphide minerals grown in the 1998-2000 time period, to see if a non-zero Δ³³S was present. We are breathlessly awaiting the results...

The Pacific Ocean is 2.5 trillion km wide

According to Cosmic Variance, the Bones episode on which Sean consulted was transmitted at 8 pm on 9 April 2009. On 12 July 2009 this broadcast was received here in Australia, where I watched the show.

Because TV transmissions are electromagnetic radiation, and travel at the speed of light, we can use this delay to determine the distance between California and Australia. The delay was 94 days, which is 0.26 years. So the distance is 0.257 light years. This is about 2.4 trillion kilometers, or 16,000 astronomical units. Thus the width of the Pacific Ocean (which separates California and Australia) is slightly larger than the distance between Proxima and Alpha Centauri, in the closest stellar system to our own.

Now, some of you may find this hard to believe. After all, surely if you can’t clearly get channel 6, then a TV transmission from 2 and a half trillion km would be hopeless, right?

Not necessarily.

Here in Canberra, our NASA Deep Space Network is currently tracking Voyager 1 at a distance of 110 au. This is 147 times closer than California. Assuming that radio transmission strength follows an inverse squared distance law, the signal from a California radio station broadcasting from the edge of interstellar space would be 22 thousand times weaker than that from Voyager 1 for a given transmitter power.

Luckily, that power is not constant. Voyager 1 has a 20 watt X-band transmitter. In contrast, San Francisco’s KCNS (UHF channel 38) pumps out an effective radiated power of 5000 kilowatts; 250,000 times more power. As a result, even at the astronomical distance at which California lies, the TV stations there still have up to ten times more signal than the old space probe.

Thus, my interpretation of California being on the outer edge of the Oort Cloud is entirely plausible.

The take home message, of course, is that when people accuse Californians of being way out there, they are vastly understating the situation…

Asteroid 2008TC3 is now the Almahata Sitta meteorite

For decades, geologists have classified meteorites based on their geochemistry, and astronomers have classified asteroids based on their reflectance spectra. Until now, these have been difficult to cross-correlate. To do so requires one of two methods. The first is to build a robotic spacecraft to land on an asteroid, pick up a piece, and safely return it to the Earth. The second is to find an asteroid on a collision course with Earth, and then pick up the pieces after the impact. This paper uses the latter approach.

Emily and Amir over at the Planetary Society have excellent write ups. Have a look if you haven't seen them. The smoke trail pics are particularly cool.

For long time fans of the lounge, this result shows that my estimate was 22 km NW of the main debris field, and 12 km NNE of the closest fragment. Had I remembered to move south by tan(latitude) x altitude from the apparent fireball location, I might have actually picked it. Now you know why I'm not a structural geologist.

I think it's fantastic that three of the Sudanese are high in the authorship list, and that they involved their undergrads on the project. Opportunities to do cutting edge science don't come along all that often for undergrads at African universities, and it is great that these young people were able to make a genuine contribution to Earth and planetary science. The nature paper is a fairly easy read, for those with access.

The paper briefly mentions that some of the carbonaceous matter in this meteorite was diamond. I referenced a couple of ureilite diamond papers in my thesis; they are considered classic examples of impact-formed diamonds.

Of course, the wonder of this discovery inevitably brings in discussion of missiles in space to deflect future impactors. I would like to go on the record as against such projects.

First of all, they would deprive us of great science, like this.

Secondly, the missiles and bombs inevitably nominated as the tools of choice for asteroid deflection are way more dangerous than asteroids are.

Thirdly, any technology which can deflect an asteroid away from the Earth can deflect an asteroid from one part of the Earth to another. We have enough ways of killing each other already.

And finally, bolide's don't kill people. Volcanoes do. And nobody wants to blow them up.

We don't blow up tsunamis, or hurricanes, or river floods either. We predict when and where they are going to happen, tell people to get out of the way, and then fix the damage after the event. There is no reason the same procedure can't be used for impactors, once early detection and prediction becomes commonplace. Given any sort of discount rate at all, a warning system will be far cheaper, safer, and saner than building a multi-zillion dollar doomsday bomb to deflect the asteroid.

Meteorite detection will only improve with time. In fact, I suspect that within my lifetime, an Earth-impacting object on a collision course with an accessible part of the developed world will be detected at least 24 hours in advance. I am even prepared to make a prediction about the first such event. That is this:

Once the orbit is calculated, and the target and time is announced, more people will travel into the target zone than away from it. I might even be one of them.

Jenniskens, P., Shaddad, M., Numan, D., Elsir, S., Kudoda, A., Zolensky, M., Le, L., Robinson, G., Friedrich, J., Rumble, D., Steele, A., Chesley, S., Fitzsimmons, A., Duddy, S., Hsieh, H., Ramsay, G., Brown, P., Edwards, W., Tagliaferri, E., Boslough, M., Spalding, R., Dantowitz, R., Kozubal, M., Pravec, P., Borovicka, J., Charvat, Z., Vaubaillon, J., Kuiper, J., Albers, J., Bishop, J., Mancinelli, R., Sandford, S., Milam, S., Nuevo, M., & Worden, S. (2009). The impact and recovery of asteroid 2008 TC3 Nature, 458 (7237), 485-488 DOI: 10.1038/nature07920

The habitable planet bubble

Greg at Oklo.org has recently put a price on terrestrial planets, as the successful launch of the Kepler telescope has piqued various people's interest in these worlds. More recently, he has announced a prize for the first planet to exceed a million dollars on his pay scale. Just for comparison's sake, he rates the Earth at 4 quadrillion dollars on this scale, while the small, cold Mars comes in at a paltry 13 grand. No currently known exoplanet can even match this value, with Gliese 581b maxxing out at just over $500. However, there is at least one low hanging fruit.

A few weeks ago, coming home from work just after sundown, I noticed a bright terrestrial planet hanging low in the western sky. As I am a women's tennis fan, I decided to name this planet after my favorite player.

The value of Venus in the oklo.org valuation is strongly dependent on its calculated blackbody temperature, which in turn depends on albedo. Using the known value of 0.75, the blackbody temperature of Venus is -40 degrees C, which is chilly, but still close enough to habitable to return a handsome 348 trillion dollars.

Assuming an albedo of zero raises the temperature by almost 100 degrees to a toasty 55 degrees C. This impacts the valuation considerably, giving a total value of only 81 trillion dollars because the planet is too hot. But 0 and 0.75 are both extreme values for albedo. What if we use something more moderate?

The purpose of the exercise is to find terrestrial planets, so assuming a terrestrial albedo (0.36) seems to be the most reasonable place to start. This assumption gives an average Venusian temperature of 20 C. That's an almost identical to the current temperature here in Canberra, and a pleasant 68 F for American readers. Plugged into the valuation formula, this model for Venus returns a staggering 1.44 quadrillion dollars. In fact, this valuation is only 20 trillion dollars short of the 1.46 quadrillion dollar value derived for the Earth using the known terrestrial albedo number. This value also puts me clear of the million dollar jackpot threshold by about nine orders of magnitude.

Of course, pedantic observers may note that Venus's blackbody behavior is tempered by the fact that the planet has a thick atmosphere, which warms the surface via the greenhouse effect. We can calculate this second order effect by substituting T_eff (the model blackbody temperature- 230-330K depending on albedo) with T_real, the actual surface temperature of 737K. This drops the valuation from 1440 trillion dollars to 2.9x10^-89 dollars, or 2.9x10^-87 cents. But in the current financial environment, a mere 104 order of magnitude decrease is not a problem. Rather, it is a badge of honor. Who wouldn't want ten thousand googles in times like these? Were I an investment manager instead of a geologist, I could use that as a justification for a million dollar bonus paid by congressional bailout.

Compared to this planetary overvaluation, the housing bubble is imperceptible.

Here are the values for some other solar system objects:
Moon: 7x10^-25 dollars. (size matters)
Europa: 7x10^-47 dollars. (This makes the JIMO EJSM program 56 orders of magnitude over budget)
Ganymede: 1.2x10^-37 dollars. (The European half of that mission is relatively thrifty)
Titan: 9.5x10^-44 dollars. (compare this with Greg's hypothetical exomoon)

Fermi paradox meets the timescale

John over at cosmic variance has been discussing extra-terrestrial life, so I figured I'd put a geologic spin on it. Specifically, look at the Fermi Paradox through the lens of deep time. The Fermi paradox states, "If advanced aliens are common in the galaxy, where are they?" More specifically, why aren't they here. As a geochronologist, I don't wonder where and why, I wonder when. So let's make a few assumptions:

Suppose that Earth has been visited by aliens 50 times since our solar system's accretion disk started to cool 4,567 million years ago. What would the aliens have seen? In order to simulate this, I generated 50 random alien arrival times in between then and now, sorted them, and put them in geologic context. They are listed below, in stratigraphic order.

Time (Ma)	Time (name)	My comment	Alien's comments
125	Cretaceous	Dinosaurs!
270	Permian	Gondwanan glaciers and funky reptiles
352	Carboniferous	Swamps and really big insects
668	Cryogenian	Pre-Marinoan- no sponges yet
675	Cryogenian
701	Cryogenian
748	Neoproterozoic
750	Neoproterozoic
808	Neoproterozoic
925	Neoproterozoic
1021	Mesoproterozoic	Grenville	Big Mountains
1049	Mesoproterozoic	Grenville	Big Mountains
1300	Mesoproterozoic
1355	Mesoproterozoic
1533	Mesoproterozoic	Mt Isa is forming	If these aliens came for resources, they didn't want base metals
1684	Paleoproterozoic
1857	Paleoproterozoic
1888	Paleoproterozoic
2159	Paleoproterozoic	Trans-Amazonian orogeny
2247	Paleoproterozoic	Various poorly constrained glaciations in this general timeframe
2272	Paleoproterozoic	Various poorly constrained glaciations in this general timeframe
2355	Paleoproterozoic
2358	Paleoproterozoic
2400	Paleoproterozoic
2459	Paleoproterozoic	Oxygen just starting to leak into the atmosphere, Manganese and BIFs
2610	Neoarchean
2612	Neoarchean
2631	Neoarchean
2661	Neoarchean
2682	Neoarchean
2745	Neoarchean
2948	Mesoarchean
2956	Mesoarchean	These two mesoarchean visitors missed each other by only 95,000 years.
2956	Mesoarchean	These two mesoarchean visitors missed each other by only 95,000 years.
2972	Mesoarchean
2990	Mesoarchean
3152	Mesoarchean
3281	Paleoarchean
3609	Eoarchean
3614	Eoarchean
3641	Eoarchean
3647	Eoarchean
3669	Eoarchean
3828	Eoarchean
3837	Eoarchean
3875	Eoarchean	LHB	Dynamical instability of this system precludes the development of complex life
3947	Eoarchean	LHB	Dynamical instability of this system precludes the development of complex life
4011	Hadean
4266	Hadean
4425	Hadean	Moon forming impact	"That's not a moon, that's a battlestation"

As you can see, for aliens looking for 'Earthlike' planets, the actual Earth was easy to overlook for msot of its history. In this simulation, there was only macroscopic life for 3 of 50 visits. From another POV, three visits were eaither during the Late Heavy Bombardment, or during the moon forming impact- both of which would appear (to the casual alien visitor) to make long-term viability of life on Earth pretty unlikely.

So as we start to find 'earth-like' planets in our sky surveys, it is important to remember that Earth has only been Earthlike for a relatively short period of time.

Dirty secrets

It seems that my secret zircons are also obscene. This morning the client called up wondering where the results he wanted were. I emailed them last week. He hadn’t gotten them. A morning spent breaking a work email down into its component thoughts showed that his server thought my research was pornographic. Evidently the juxtaposition of ‘single’ and ‘dating’ in the same message was enough to classify my geochronology summary as pornography. I might email their webmaster and tell them their program is fucked- will the message get through?

Astronomers see Martians fart

Astronomers have detected huge plumes of methane on Mars, which may have a biological origin. Further work needs to be done, which will include spectroscopically analyzing the various associated sulfur species. This will allow sophisticated computer modeling simulators to digitally reconstruct the smell, which will be used to differentiate between biological and geologic processes. See Universe Today or The Planetary Society Blog for more mature interpretations.

Wrong target?

Evidently the new “The Day the Earth Stood Still” remake features hyperadvanced aliens who come to Earth to get humans to stop damaging the planet, or else.

At Cosmic Variance, Sean discusses the philosophical implications of intergalactic ecoterrorists such as these. While at Systemic, Greg points out the futility of beaming a signal to a star that set two hours before the transmission begins. I have a different angle.

I reckon these aliens have picked a soft target.

As CV’s commenters have pointed out, paleontologists have identified 6 mass extinctions which exceed a threshold value to qualify as ‘great’. The sixth extinction is allegedly being caused by us. Which means that exterminating humans is at best a 17% solution. It does nothing to address the other five extinctions. Our current best guess is that those other five were primarily caused by flood basalt volcanism (with an accessory role for bolides). Which means that humans are merely a biocidal sidekick, compared to this:

Therefore, if aliens with superpowers want to properly protect diversified marcofaunal ecosystems, they shouldn’t kill us. We may be messy, but our common enemy is the mantle plume. Aliens serious about reducing the risk of ecological catastrophe should instead eliminate thermal instabilities at the core-mantle boundary. To do anything else would be a 1/6 measure. And they can even ask these guys for technical tips.

The geologic lifespan of Jon Bon Jovi

As a child of the 80’s, I grew up with a variety of ephemeral pop bands, who evolved from the primeval ooze, burst into an eruption of sound and video fury, only to fade into extinction. Occasionally, however, a rare artist would rise again from the depths of obscurity, a rock and roll coelacanth long after his contemporaries had lithified. After a recent sighting of one such musical living fossil, I began to wonder exactly how long this antiquated creature could reasonably be expected to survive. So in an exercise of Bon Jovichronology, I tried to deduce the musical lifetime of Bon Jovi using the principles of geochronology and some of his better known lyrics.

While the title of the song “Always” is obviously an unquantifiable hyperbole, there is a refrain from which we can attempt to derive an answer.

I’ll be there ‘till the stars don’t shine
‘till the heavens burst
And the words don’t rhyme

Thus, a Bon Jovi-eon is allegedly comparable to the lifetimes of stars, heavens, and rhyme. What are these in years?

The lifetime of the stars that shine is an astronomical question, not a geologic one. All of the stars we see right now are either
a. Short-lived massive stars,
b. Giant stars inflated by the last gasp of helium burning at the end of their lives
c. Sunlike stars that happen to be passing close to the sun right now.

Or some combination of the three. In any case, all of the stars that we can see today with the naked eye will either die out or move too far to see within millions to tens of millions of years. It is worth pointing out that the most common, longest lived M class stars are too dim to view unaided, even if they are very close. Of course, once the stars we see today disappear, they will be replaced by other, different stars. Sunlike stars are being born today, and they live for 10 billion years, so there will probably be something to be seen in the night sky for tens of billions of years, long after our sun runs out of hydrogen and swells up into a red giant, evaporating all the FM radio stations and record stores that may still exist on Earth. So this constraint is pretty open-ended.

It is hard to quantify when the heavens will burst, as heaven is a mythological/literary construct. Taken literally, this would presumably refer to Armageddon, which has a timescale of a few thousand years- orders of magnitude shorter than the stellar constraint.

So, what about the third constraint? While the timescale of rhyme is a linguistic question, we can derive a quantification from standard geochronological first principles. To do so, we will assume the following:
1. A rhyme is deemed to have decayed when the pronunciation of the words changes so that those which used to rhyme don’t anymore.
2. Like radionuclides, we will assume that the rhyme decay constant is invariant. It almost certainly isn’t, since audio recordings and dictionaries will probably effect it, but that doesn’t mean that we can’t pretend.
3. Rhyme decay is irreversible.
Using these assumptions, we can take an English language work of known age, and ratio the remaining rhymes to the original rhymes to determine the decay constant, lambda. The relevant equation is lamba = -ln(N/N₀)/t, where N is the remaining rhymes, N₀ is the original rhymes, and t is elapsed time. Lamba is related to the half life, as follows: T_1/2 = ln2/lamba. To calculate the English rhyme decay constant, I will use a subset of Shakespeare’s sonnets, published in 1609. Looking at every tenth sonnet, we see that out of a total of 210 rhymes, 12 have decayed, and 198 are intact. –ln(198/210)/400 gives us lamba=0.000147/yr, or a halflife of 4712 years. This is slightly shorter than the halflife of carbon-14.

A approximation is that after 10 halflives, 99.9% of a nuclide has decayed, and the original has generally dropped below detection limits. Applying this to Bon Jovi suggests that after 47,120 years, essentially all of the words that currently rhyme won’t.

For comparison, this is approximately the elapsed time since humans first arrived in Australia. Europe was still inhabited by the Neanderthal, and it would be 20,000 more years before Cro-Magnon people painted their caves. A similar period of time would have to elapse after that before this descendant of subsequent African emigrants invented rock and roll.

Of course, for the cynics among you, there is an alternative explanation.
Technically, shine and rhyme don’t rhyme right now. The heavens burst whenever it rains, and to the sea level observer, the stars stop shining just before sunrise.
So a jaded reader could interpret this as a one night stand song. This interpretation is irrelevant for two reasons.
Firstly, the known timescale of Bon Jovi’s success is 3-4 orders of magnitude longer than a single night.
More importantly, though, is the observation that during the 80’s, jaded cynics weren’t listening to Bon Jovi; they were playing records by the British black tee-shirt crowd instead. I should know. I was one of them.

related post: Postdoc song

How astrophysicists spoil cosmochemical parties

As I mentioned a while back, the presence of short-lived radioactive nuclides in early solar system material means that a nucleosynthetic event must have occurred shortly (< a few million years) before these materials formed. The simplest explanation for this is that a supernova occurred, in which these elements were produced. This supernova then injected these materials into a nearby molecular cloud, and the force of the shockwave triggered the collapse of this cloud to form our solar system. It all makes a good story, and the simplicity of the model makes interpretation of cosmochemical data more straightforward than a complicated model would. The problem is, a gang of unruly astrophysicists eventually found out about it and attacked it with calculations. Gounelle and Meibom were particularly savage.

Their paper is basically argued like this:
1. injection and collapse from a single supernova is unlikely.
2. contamination of a circumstellar disk in unlikely (this is the hypothesis they discuss in detail).
3. Therefore, the excess short-lived nuclides must have been inherited from the stellar medium, or formed from spallation or other non-stellar processes.

The argument against single-supernova injection and collapse is fairly simple. Basically, the computer says "No".

Specifically, they argue that models show that fast supernova ejecta will disperse the cloud instead of collapsing it, while low speed ejecta will not penetrate the cloud, so injection does not occur.

They then turn to the supernova ‘salting’ of a circumstellar disk.
The problem here is that prior to blowing up, stars that are big enough to end in supernovae are very luminous and hot, and thus emit a huge amount of UV. This UV will evaporate any disks nearby on timescales shorter than the life of the massive star. So by the time the star blows up, there is no disk left to inject materials into. They calculate that the probability of a disk surviving long enough, but still being close enough to receive sufficient material, is very small.

Having thus shown these two most popular theories to be unlikely, they conclude that spallation is the best hypothesis for ²⁶Al and other short lived nuclides, while the longer lived ones (halflives > a few million years) live long enough to have been present in the interstellar medium before star formation.

I generally don’t like elimination-based arguments for poorly constrained problems like this one. In order for not 1 and not 2 to imply something, you have to also exclude the possibility of a door number 3. Additionally, they made the mirror image mistake of cosmochemists- despite their expertise in star formation, they don’t acknowledge that meteoritic concentrations of ¹⁰Be (which has to be spallation related) and ²⁶Al are not correlated, at least in CAIs. This suggests that the origin of ²⁶Al is not spallation.

But while I disagree with their argument, the bigger picture is still important- meteoriticists can’t just sit in a lab measuring obscure isotopic ratios without verifying the astronomical plausibility of our chemically-derived models. Like it or not, it is in our best interests to actually talk to these people, even if their skill sets, publishing habits, and scientific culture is different and strange. Because despite the vast differences in methodology between high-precision isotope geochemistry and whatever it is that astronomers actually do, we are in fact attacking the same problem: How do stellar systems form.

Matthieu Gounelle and Anders Meibom 2008 THE ORIGIN OF SHORT-LIVED RADIONUCLIDES AND THE ASTROPHYSICAL ENVIRONMENT OF SOLAR SYSTEM FORMATION The Astrophysical Journal, 680:781–792

Matthieu Gounelle, Anders Meibom (2008). THE ORIGIN OF SHORT-LIVED RADIONUCLIDES AND THE ASTROPHYSICAL ENVIRONMENT OF SOLAR SYSTEM FORMATION
The Astrophysical Journal

Gender inequity in the Olympics

Well, the games are finally over, so all you Americans get go ahead and forget the metric system for the next 3.95 years. But now that the results are in, I thought I’d play with the numbers a bit.

The official website breaks the medal tally down into men’s and women’s events. Looking at the statistics, I noticed that a few countries were much more successful with one gender than another. There aren’t any sensible biological or geographic reasons for why this might be the case, so I decided to graph up the results just to see who fell where. Weighting the medals so that gold=3 bronze and silver=2 bronze, I calculated the fraction won by men.

I call this number the chauvinism index, as it seems to reflect the extent to which female athletes are not brought up to the same standard as their male counterparts. So a country with male medalists and no female medalists would have a chauvinism index of 1, while one with only female medalists would have a chauvinism index of zero. One minus the chauvinism index would of course be the emasculation index, and a perfect balanced nation would score 0.5 on both scales.

The Chauvinism index for all countries with ten or more total medals is shown below:


As you can see, the French are the biggest chauvinists, while the Dutch are most pussy-whipped. As if we didn’t know that already. Note that we expect the average to be greater than 0.5, since there are more men’s events than women’s events. Extracting trends or cultural significance is left as an exercise for the reader.

Do Muslim clerics need a holiday?

According to this BBC report (hat tip frenzyj on the livejournal geology feed) various Muslim activists are calling for adoption of Mecca time instead of GMT. For the sake of this argument, we will ignore the fact that time is now measured using UTC, which is based on an atomic clock, and has replaced GMT. Instead, their argument for Mecca time is far more amusing.

One of the arguments that is brought forth at their meeting (by an anonymous geologist, no less), is that Mecca’s longitude is in perfect alignment with magnetic north.

This is not correct. Mecca actually has a magnetic declination of about 2 degrees E. But the argument is an interesting one. London, after all, is a dreary place, and if a sunnier locale with 0 magnetic declination could be found, we might all be better off adopting their lifestyle and time zone.

Well, such a place does exist. The city of Montpellier, on the French Riviera, currently has a declination of zero. So perhaps it is the relaxed Mediterranean lifestyle to which these Muslim activists secretly aspire. If we were all to adopt Montpellier time, complete with 30 hour work week and mandatory relaxing by the sea, then maybe all this bombing and shooting that troubles the globe at the moment could be avoided.

What makes Earth Earthlike?

As astronomers get ever more precise in their measurements of stellar wobbles and light curves, the date of terrestrial exoplanetary discovery is slowly creeping up on us. There will no doubt be a big to do when the first one is found, and the press will undoubtedly make a huge deal of it’s Earthlike nature. But as a surface dweller, I have to wonder. Sure, an iron core and a magnesiosilicate mantle will give a bulk composition broadly similar to Earth. But will the planetary surface be anything like the one we have here? And how similar does it have to be to be considered Earthlike?

Do we need an ocean? A moon? A magnetic field? A thin crust that can be easily subducted? A carbonate silicate cycle? And what about the more subtle things?

If the Earth had a composition that produced dominantly alkali basalt instead of tholeiite, would we still have sialic crust and quartz beaches? If star formation was triggered by something other than a supernova, would there be sufficient heat-producing elements to melt planetesimals and allow for early differentiation? What happens to the inner solar system if your gas giants aren’t as gentle as ours are?

I’m ignoring the question of life on purpose, because there are lots of people already obsessing over that. It may be that there are billions of inhabited planets that are completely unearthlike in any meaningful way. It may be that there are millions of terrestrial planets indistinguishable from the Archean Earth except that they’re dead. What I want to know is how much variation there can be in an iron-silicate ball of 10²⁴-10²⁵ kg in mass, and what are the important factors in determining that variation.

Because ultimately, the question, “Is there anywhere else much like this place?” is an obvious corollary to the fundamental one of, “Why are we here?”