Sunday, December 21, 2008

Merry Christmas

It's the longest day of the year, so I'm off to holiday on the oceanic crust for two weeks.

I hope you all have wonderful holidays, and a great new year. Here's a picture of LLLL testing the stability of our home-grown Christmas tree and $8 DIY stand:

Wednesday, December 17, 2008

The zircon who knew too much: Retrenchment blogging, day 42

I have just been offered a 6 month geochronology contract with Geoscience Australia. The aim is to help them work through their backlog of U/Pb ion probe zircon dating. The contract says that a security clearance is required. Now, I don’t know what state secrets these mineral grains hold, or how bombarding them with 10KeV O2- ions will reveal this information, much less endanger the operations of the Australian government. But you won’t find out from me. Loose lips sink ships. And they wreak havoc on high vacuum systems when you try to pump them down. So mine are sealed.

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.

Saturday, December 13, 2008

Spot the geologists

Back when the minerals boom was booming, I and many other geologists had stories of being approached for employment in unusual circumstances. For example, in July of 2007, my Managing Director and I were buying groceries for a field expedition in a Mt. Isa supermarket. A random guy walking down the aisle greeted us, allowed us to introduce ourselves, and then asked me if I wanted to come work for him. This was despite the fact that I had just introduced the MD as my boss, and he was standing right there.

I don’t know how he identified me as a geologist. A theoretician might be able to derive a geologist spotting formula (GSF) from the laws of thermodynamics, but I’m an experimentalist. So I will experiment. The following link is my public facebook page.

Note! Updated methodology!

If you, the reader, are on facebook, you will be able to click through to my friend list. Don't do this! Friend lists can contain information that may bias your picture analysis.
Instead, view the selection of 8 random friends of mine who will be apparent in the public page. In order to participate in this geologist spotting experiment, all you have to do is the following:

1. Look at the sidebar of this blog to determine my blogular email address, and compose an email to me.
2. Look at the pictures of some of my friends.
3. Cut and paste their names into your email, followed by a YES if you think they are a geologist, or a NO if you think they are not.
4. If you know the person, please say KNOWN instead of typing yes or no.

If you're really bored you can go through my whole friend list, but a few dozen per person ought to be plenty. Clicking the reload/refresh button on your browser will change the 8 people shown on the public page. So just reload a few times until you feel you've sampled a representative number of people, or until you get bored.

In order to give some vague semblance of privacy to all the friends of mine whom I have just turned into an online viewing gallery, please don’t post any names in comments. Use email instead (comment moderation is now on, just in case). I’ll post statistical spotting results devoid of personal identifiers as data come in.

So don’t be shy, don’t lurk, and please participate in this geologist spotting experiment. Otherwise, we’ll have to defer to the theorists for possible explanations. Statistics on how many of my friends I piss off by doing this may or may not be collected.

Space is so big...

That is can host dozens and dozens of carnivals.

Carnival of space #81.

Carnival of space #82.

Wednesday, December 10, 2008

Rio to slash 1.4x104 jobs

Rio Tinto is letting go 14,000 people in an attempt to reduce debt and react to rapidly deteriorating market conditions. This is:
-60% of the population of Alice Springs.
-20% more than the entire attendance of next week's AGU meeting.
-One person per month since the reign of Charlemagne.

Monday, December 08, 2008

Math for geologists

Because ultimately, everything in our science comes down to beer.

Sunday, December 07, 2008

Lead in plastic

A few weeks back, shortly before my job with Uramet terminated, the chief geo and I were doing some work out at the Geoscience Australia core library. I took the opportunity to grab the portable XRF analyzer, and check the old, peeling paint on out railings for lead. The good news is that they were not Pb paint- the Pb content was measured in ppm, not percent.

Not content to turn the machine off with my peace of mind intact, I decided to move on to the windows. When we bought the house, we replaces all the old, leaky, single-pane aluminum windows with swish double-glazed uPVC windows. I’d head something about metals such as lead being used in some plastics, so I figured I’d take a look. A spectra is shown below:

The dominant peak is the chlorine peak. Since PVC stands for polyvinyl chloride, this is not surprising. The Ti is probably related to the white pigment. And there is also substantial calcium and lead. I don’t have a standard to compare this to, but the instrument’s built-in, assume-it’s-a-crustal-rock firmware estimates 1-2% Pb.

So from now on, LLLL is not allowed to chew on the windows. Aside from that, though, I don’t really know what to make of this. I know fuck all about plastic stabilization, much less how it is regulated. So I don’t have the environmental knowledge required to calibrate my level of parental worry. If anyone better educated than I wants to pitch in, that would be great.

Friday, December 05, 2008

Retrenchment blogging, day 30

I'm unemployed!

Also, a bit tipsy.

And yesterday, I got an official job rejection letter. It was from a government agency, and they can only hire permanent residents if no qualified Australians apply. So that was pretty much expected. Still. Anyway.

I had a good chat wth everyone else who got sacked today- the board stopped operations, so everyone from the managing director down to the fieldies is looking for work. Maybe if we'd driven a prius to Washington they would have bailed us out. Oh well. The chairman has a point, which is that if good results don't raise the shareprice or atract investment, there isn't much point spending the money needed to get the results. Still, it is a bit frustrating to have to walk away from half finished projects. Oh well. Welcome to the real world. I leave it to a junior geo 10 years from now to dig up our reports and ask his boss, "Why didn't the drill this one out?"

In the mean time, anyone with 5 cents in their pocket can pick up not one, but two shares of uramet stock. It floated at 20 cents.

Tuesday, December 02, 2008

A tip for science writers

Currently, a story about the Hadean Earth is the banner article in the science section of the New York Times. This is good. As the article explains, the Hadean- formally the time from Earth’s formation to 4 billion years ago, and informally the time for which we have no rocks- is traditionally underconstrained (no rocks, no data). But in the last few decades, rocks and individual minerals have been found, and the picture that is emerging is that the Hadean may have been more similar to the modern Earth than originally thought.

This is all well and good, and I have no argument with the science or the presentation of it. People in the know have known about evidence for a wet early Earth for years, and the New York Times is a good place to get that knowledge out into the wider human community. However, I have a complaint about the way the reporting was done, which could prove problematic with a more contentious topic.

The writer of the Times piece writes:

“The picture that’s emerging is a watery world with normal rock recycling processes,” said Stephen J. Mojzsis, a professor of geology at the University of Colorado who was not involved with the U.C.L.A. research.

Mojzsis’s name is not on the paper, and he may have been unaffiliated with this particular project. However, a quick Google scholar search will show that he and Harrison have co-authored a dozen papers over the last decade or so on early earth evolution. Several of these papers include work done on Jack Hills zircon, which is the topic of the Nature paper at the heart of the article. So presenting his opinion as that of an uninvolved, detached scientist is probably a bit of a stretch.

I don’t know how much training or education science journalists get with regards to the culture of scientific collaboration, but simple tests like reading the names on a publication list will at least give a hint as to how connected or independent various scientists are.

As an aside, Harrison and Valley did not discover Hadean zircons. That was done in the early eighties. What happened in 2001 was that both groups developed (independently) the ability to measure oxygen isotopes on single zircon grains to the precision needed to make inferences about the source magma of the zircon.

And anyone wishing to know more about the state of research into the Early earth should get to San Francisco in the next week and a half. There are several sessions at the annual fall AGU meeting.

Monday, December 01, 2008

Are they looking back?

Thus far, science has discovered planets around more than 250 stars. Most of these are too faint to see without a telescope, but a couple are quite bright, and several others can be found if you know where to look. Currently, a couple of these are high in the Southern sky. Fomalhaut, with a recently imaged planet that has been blogged everywhere, was just about directly overhead in November at sunset, and is now just a bit west. Click the image to see the stars in question.

Also visible is Epsilon Eridani, which is the closest star with a known planet. It is fairly dim, so despite being only 10 light years away, it is an inconspicuous star, the second in a line of four stretching away from Rigel up and to the north. So far, only huge gas giants have been detected. But these systems almost certainly have rocky planets or moons with outcrops waiting to be mapped.

Friday, November 28, 2008

Movember final weekend

I've mowed my face down to just the mo now, for the last gasp at Movember. I'd like to thank both of the regular readers who have donated thus far. If anyone else wants to do so, the following link should take you to the donation page:
Please give generously.

Wednesday, November 26, 2008

The geology of Plymouth Rock

Plymouth Rock, where the Mayflower pilgrims allegedly alighted on the new world, is a large boulder of Dedham granite. Like the pilgrims, this granite has traveled.

It is a glacial erratic, meaning that it was scraped off the ground and picked up by a glacier, and it then dropped into its current position when the glacier melted during the waning years of the last ice age. The Dedham granite from which it is derived is a neoproterozoic intrusive that forms much of the crystalline basement of the Esmond-Dedham terrane.

This terrane forms the bedrock of much of eastern Massachusetts and most of Rhode Island. The 680 Ma granites intrude older clastic sediments, which contain predominantly Grenville-aged zircons. But the basement on which those sediments settled is a mystery.

The Esmond-Dedham does not just have a mysterious bedrock; it has an exotic origin as well. It is an accreted terrane. It is a sliver of the southern supercontinent of gondwana, and only arrived at its present North American position in the last gasp of the Alleghenian orogeny, the last of the three mountain-building events that formed the Appalachian mountains.

So when the pilgrims stepped onto that rock, those transported souls were disembarking onto an erratic dropstone of a microcontinent, which itself had traveled from Africa, back before the Atlantic Ocean even started to form.

Here on planet earth, even the solid ground moves around the globe. Splitting, sliding past, colliding and attaching to each other, these continental fragments travel around the globe at the whims of convection.

In is not in the nature of this planet to be static; we leave that to the dead moons and asteroids of the solar system. But for an evening, tomorrow, we can cease our wanderings, and gather together for company, cheer, chow, and thankfulness. Unlike Plymouth Rock, most of us are not born of lava, witnesses to the birth of mountains and seas, and surfers of continental glaciers. But we can all tell stories, give thanks, and enjoy this great American holiday.

Happy Thanksgiving.

Monday, November 24, 2008

Super-sized sandbox

Sometimes, having a daddy as a geologist isn't too bad.

Friday, November 21, 2008

Retrenchment blogging, day 16

Nobody has requested any science posts, so I guess I should fill in the story of my job quest. I took my Mo on a tour of a prospective employer’s lab yesterday, and it didn’t seem to deter them too badly, which is good. Today, I had lunch with a former student from my lab tech days, who is now working in the geol survey’s geothermal section. This was not a direct job interview- or even a hunt for leads, but rather an information-gathering exercise in order to figure out who does what and how the industry works. Just because a company has a geothermal lease doesn’t necessarily mean that they employ field geologists. Some do, others contract out all of their actual dirt-involving services to service companies. Understanding who does what allows one to target the correct potential employee. And it's always nice to have an excuse catch up with people and see how they're going.

Tonight I need to apply for something for which application was encouraged- always a good sign, I suppose, but it doesn’t do to get too hopeful at this stage.

Below is my short-form resume, so all you Americans can tell me how inappropriate it is. I should get this guy tidied up in case I apply for work back home. Suggestions, compliments, and insults are welcome.

Thursday, November 20, 2008

Friends don’t let friends wear lamb chops

With Movember approximately 2/3 over, my ability to raise funds by looking even uglier than usual has been only marginally effective. While charity is not a competitive activity, I can’t help but point out that of all Australian Mo bros, I am currently the 28,100th most effective fundraiser. There are fewer than 50 towns in all of Australia with 28,000 people in them. So I think it is time for some incentives. For $20, you can nominate an area of facial hair to remove next. For $50, you may nominate a topic to be blogged here at the lounge. And for $100, you may do the same as for $20, but without the constraints of bilateral symmetry. But don’t give money because you want me to look funny. Do it for the depressed prostate sufferers.

Tuesday, November 18, 2008

Green energy dustup

Many people advocate putting large solar powerstations in arid regions. The reasoning behind this idea is that the land isn’t much good for anything else, and that the low rainfall will mean few clouds and high insolation. Trouble is, a lack of clouds does not necessarily mean that a lot of light is reaching the ground. For example, see the picture below.

This is a cloudless desert morning, and yet, the poor solar panel shown is producing very little power. The reason, of course, is that a dust storm is blanketing everything in yellow gritty haze. During the winter, the solar panel plus battery kicked the ass of our generator, which is cumbersome, old, messy, and often difficult to start. But after a day of hot dust, we had to recharge the battery from the car, and eat whatever meat had thawed. Cleaning it the next day was a bit of a pain as well.
On the other hand, a wind turbine would have been awesome, at least in the short term. I suspect that the full sized suckers, if installed in this environment, would eventually create dune deposits in their wakes. And the sandblasting probably wouldn’t do the rotors and bearings any favors either.

Monday, November 17, 2008

Retrenchment blogging, day 12

I formally submitted a job application yesterday to Geoscience Australia. Since the Australian government only hires permanent residents as an option of last resort, I suspect my chances are slim, but it looked like an interesting opportunity and was good practice for the world of official applications, form filling in, and other trappings of big organizations.

We'll see what happens. I won't post many details of job applications while they are pending. Might not be prudent, y'know.

Saturday, November 15, 2008

Retrenchment blogging, day 10

And now, to address the serious problems.
What am I supposed to do with all of these?

Friday, November 14, 2008


Movember (The Month formerly known as November) is dedicated to raising awareness and funds for men's health issues. Specifically, prostate cancer and depression. As with many activist causes, this is done by horrifying people. We horrify people by growing hideous mustaches. According to the rules, one is supposed to start clean-shaven, and grow from there. But I was never much good at following rules. So I'm taking the opposite approach, and generating a mostache by subtraction, starting with a full beard. Please give generously. If I can show up to job interviews like this, you can spare a fiver. All donations over $2 are tax deductible.

Thursday, November 13, 2008

Retrenchment blogging, day 7

Day 2 was mostly resume updating and tracking down references.
Days 3 and 4 were a long planned trip away.
Day 5 was gathering info on a specific field in which I have no experience or contacts.
Day 6 was talking to a guy at a largish gold company about resumes, corporate mindsets, and how to professionalize general field mayhem.
Day 7 was mostly catching up on actual work.

Resumes give me the shits. As they are cultural artifacts, doing them in another country gives me the shits even more. My secret day six contact was very pleasant at pointing out that what I thought was my long format, Australian style CV was several pages too terse, and completely devoid of the catch phrases and buzz words required to woo the eyes of management and HR.

I’ve always been of the opinion that buzz words are a key indicator that the user has no idea what he it talking about. But what I took away from that meeting was that, in large organizations, the people with the power to hire don’t have any idea either. This these catch phrases serve as a shared delusion- a cult of murky grammar- to facilitate a shared mindset and outlook. So if I want employment at such an organization, I need to pinch my nose, drink the kool-aid, and develop an understanding of opportunities and needs of stakeholders relevant to the actionable efficiencies and outcomes.

Why keep up with the Jonses when you can name your town after them?

Tuesday, November 11, 2008

Opal on Mars

ResearchBlogging.orgMilliken et al. 2008 claim to have discovered opal on Mars. They used high resolution satellite-based IR spectra.
IR spectra show absorption that is caused by the vibrational frequency of molecular and crystallographic ionic bonds. In this case, it is the Si-OH, OH, and H2O bands that were characteristic. Opal is not the only hydrated silica on Mars, but the exact energy of the various bonds is dependent on crystallographic and compositional constraints. Spectra of various silicates were taken, and opal was found to be a better match than sheet silicates or hydrated volcanic glass (e.g. obsidian). The details are in the data repository, to which I do not have access.
Various popular articles have suggested that this is evidence for surface water or hydrothermal alteration on Mars. Neither conclusion is sound. Opal generally forms in low temperature environments, and is easily dehydrated at modest temperatures. Here in Australia, it is generally precipitated by groundwater in areas that have been arid (more evaporation than precipitation) for millions to tens of millions of years. However, it is still significant.
Opal is not thermodynamically stable. As a hydrous amorphous phase, one might expect it to alter over a billion year timescale. This means that either it fails to devitrify for potentially interesting reasons, or it is young. These alternatives are generally testable. This is because opal often has high U contents and high U/Pb ratios, allowing for U/Pb geochronology to be performed (e.g. Amelin & Back 2006).
An aerial or satellite gamma ray survey should be able to identify any potential uranium enrichment, as long as the spacial resolution is as fine as the outcrop extent. If present, a sample return mission to an opalized paleochannel would potentially allow a minimum age to be determined, assuming that the opalization postdates the surface flow and predates the inversion of the terrain through differential erosion.
In Australia, opalized paleochannels can present as false positives in uranium exploration, due to the elevated but uneconomic uranium enrichment. I don’t have a literature reference for this though, as the information was obtained via a seminar series at the School of Hard Knocks.
Tuff cookie discussed this a few weeks ago.

Full article:
R.E. Milliken, G.A. Swayze, R.E. Arvidson, J.L. Bishop, R.N. Clark, B.L. Ehlmann, R.O. Green, J.P. Grotzinger, R.V. Morris, S.L. Murchie, J.F. Mustard, C. Weitz (2008). Opaline silica in young deposits on Mars Geology, 36 (11) DOI: 10.1130/G24967A.1

References sited:
Yuri Amelin; Malcolm Back 2006 Opal as a U-Pb geochronometer : Search for a standard. Chemical Geology 2006, v. 232, n 1-2, p. 67-86

R.E. Milliken, G.A. Swayze, R.E. Arvidson, J.L. Bishop, R.N. Clark, B.L. Ehlmann, R.O. Green, J.P. Grotzinger, R.V. Morris, S.L. Murchie, J.F. Mustard, C. Weitz 2008 Opaline silica in young deposits on Mars. Geology, November 2008; v. 36; n. 11; p. 847–850.

Monday, November 10, 2008

Thursday, November 06, 2008

Retrenchment blogging: day 1

It has occurred to me that I will be neither the first nor the last person to lose his job during this economic cycle. In fact, if this situation becomes as severe as some predict, reaction to job loss could have a far greater audience than esoteric geology jokes. So, I am going to blog my retrenchment. Do not consider this advise by an expert- I haven't been retrenched before, so I don't really know what I'm doing. Whether this story has a happy ending or an infinite downward spiral remains to be seen. But I'll post actions, thoughts, and new as time permits, so my experience can serve as a guide- or as a warning- to future victims of economic rationalization.

Day 1. WTFH?
Last night, my manager called me up and told me that my position would be terminated in a month's time. He didn't say much more. Since I telecommute during the off season, I really had no idea what was going on, so I spent a bit of time chatting, emailing, and talking with various folks back west to see who else was effected and how. I had emailed a few close contacts or advise, and I followed that up as well. And, since I am employed for the next month, I did a fair bit of work. You know, like, my actual job. Some of that was retrenchment related, though, as I had to inform various collaborators that I wouldn't be around.

My initial strategy was to conduct wide ranging inquiries. I didn't quite call everyone I knew- that would be quite time consuming. But I picked some key high-value people and either gave them a phone call or dropped them an email (usually call first, with email follow-up if they weren't around). I also went through my business card collection- a year ago total strangers were giving me their cards in bars, grocery stores, etc and suggesting I come work for them. So I figure, might as well give them a shot. And I did the easy stuff, like contact relevant facebook friends, people in my inbox I owed mail, etc.

Many responses were pretty grim, such as "Ha. half our staff got laid off last week. sorry." In general, the people in the most similar situation (advanced degree holders with a few years experience) had the grimmest news. But unlike emails, phone calls were good in that even if the person couldn't help me, they often had positive messages which eased the worry, even if nothing concrete came of them. And several contacts did produce additional lead trees. Interestingly, one of the ex-collaborators who I called to tell him our joint project wouldn't get done came back at me with a highly promising lead, so that was a bit of unexpected good news.

It's a bit early to draw firm conclusions, but my best luck so far have been people in different businesses with whom I've had positive professional dealings. Tonight was spent updating the Resume/CV, but I can't send it out until I call my second reference and reconfirm that he's still happy to do it (It's been 18 months since I used him to get my current job). I'll probably use the long format one (shown) for closer contacts/ specific requests, and trim it down to a one-pager for cold drops on people who aren't likely to care enough to flip pages.

Wednesday, November 05, 2008

Termination Shock

1. The outer part of the heliosphere, where the solar wind slows down to subsonic speeds due to interaction with the interstellar medium.
2. The surprise caused when the boss calls during an after-hours election-celebrating beer, to say that one's job is ending in a month.

I know I promised science, but I've been busy dusting off contacts and updating my resume tonight. Science will resume when I get the time.

Complaints, leads, or suggestions for oddball careers potentially off my radar are all welcome.

Tuesday, November 04, 2008

Ya think the election will be this close?

It has always amused me that the US election date is the same as that of Australia's greatest horse race. Here's the official photo finish from this year's Melbourne Cup; Viewed nosed Bauer out by about one cm on a 3200m track. That's about 3 parts in a million. For comparison to the American horse race, if 100 million people vote today, that would be a 300 ballot difference. In science, it is extremely difficult to measure most things to that precision.

The observant among you will note that in this picture, the black horse has nosed out the one with gray hair. Interpretation of that point is left as an exercise to the reader.

Science resumes tomorrow.


Well, here we are. Assuming your time zone is sufficiently easterly, it is election day. Who will be our next President, Mitt Romney or Hillary Clinton?

The fact that this question is a joke shows just how far we have come. Both parties managed to ditch the business as usual candidates in the primaries, and nominate a couple of guys with experience and desire for reaching across the aisle for the common good.

Which one you choose is up to you; I could hum and haw forever on this topic, but I have work to do. So instead I'll just post my best guess at the end result, below. Happy election day, fellow Americans. And please remember to vote, if you haven't already.

Horse racing picks my be left in comments by Australians who are feeling left out.

Sunday, November 02, 2008

Quick journal publication etiquette question:

If a private sector researcher is submitting a manuscript to an academic journal, and said researcher is concerned that the timescale of peer review might be longer than the timescale of employment (or even employer solvency) due to the current economic situation, is it considered unprofessional to use non-work contact information?

A friend of mine needs to know what contact info to put on his paper.

Thursday, October 30, 2008

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: T1/2 = 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

Wednesday, October 29, 2008

Dick Zimmer for Senate

Dick Zimmer is socially moderate, fiscally astute, and all kinds of awesome. Let me explain, for those of you who are unfamiliar with central Jersey politics.

Dick Zimmer was the congressional representative for NJ’s 12th district* from 1990 to 1996. In 1996, he ran for the Senate seat vacated by Bill Bradley, who was retiring. Zimmer lost to democratic representative Bob Torricelli, and the congressional seat he vacated to run for senate was take by Mike Pappas.

Mike Pappas was a disgrace to the Garden State, who spent his time in congress singing love songs to Kenneth Starr. He was defeated in 1998 by Rush Holt, who is still the representative for district 12.

In 2000, Dick Zimmer challenged Holt for his old seat. In this race of two great candidates, Zimmer ended up losing by less than a thousand votes. At that point, he left politics, and spent his time teaching at Princeton University and working in the private sector as a lawyer.

In the same year, Frank Lautenberg retired from the senate at the ripe old age of 76.

In 2002, Torricelli ran for re-election to the Senate. Six weeks before the election, he was implicated in illegally receiving campaign funds from North Korea. Rather than risk losing the election, the Democratic Party pulled Torricelli’s name off the ballot, and drafted Lautenberg out of retirement to substitute in. Lautenberg won the election. This year, he is running for his second term out of retirement, or his fifth overall.

Having witnessed the rise and fall of the Ming dynasty in his youth, Lautenberg is a fan of big, intrusive government. Twenty-year-olds in Virginia or Montana can thank him for making beer illegal, as he championed the practice of withholding federal funds in order to bribe state legislatures into social engineering.

In contrast, Dick Zimmer has a socially moderate, fiscally conservative record. He supports limited, but effective government. With a 1013 dollar deficit, we need somebody who isn’t a profligate spender. Dick Zimmer won’t use your tax dollars to force people halfway across the country to live a certain way. And he won’t take is marching orders from Harry Reid. He’s a great legislator, and we’d be lucky to get him back in office.

It’s OK if you’re voting D for President and house this year. We all stray from time to time. But an R in the senate column will benefit New Jersey and the nation.

Of course, some of y’all may prefer a technoblogospheric nepotistic argument instead. In which case, I recommend you vote for Carl’s dad.

* In New Jersey, congressional districts are named after Turnpike exits.

Sunday, October 26, 2008

My congressman *is* a rocket scientist

I still support Rush Holt for congress, just like I did two years ago. Senate is forthcoming.

Friday, October 24, 2008

Geomorphology/hydrogeology question

Does anyone out there know what the world's largest intermittent river systems are? I'm not looking for wise-ass answers like "Rio Grande". I'm just wondering how common it is to have coherent drainages thousands of km in length that only occasionally carry water.

Thursday, October 23, 2008

Liquid Nitrogen for Grownups

Everyone who has ever seen a mad scientist outreach knows that liquid nitrogen is fun. You can freeze people’s balls with it, shrink balloons, cast gasoline candles, and make great clouds of fog. It was even the molecule of the day last week. But there is a little known secret side to this substance. Believe it or not, it is actually a commonly used substance for real labs doing actual work. And while we may occasionally make ice cream with it, that isn’t why our labs buy it by the silo full. So below I’ll go through a couple of the actual scientific uses of LN2.

1. IR detectors. Infra red spectroscopy studies the wavelength of IR radiation given off or absorbed by various materials, depending on their composition, structure, or impurities. However, at room temperature, everything gives off a fair bit of IR radiation. So an IR detector in a microscope will detect the ‘glow’ of the surrounding instrument- as well as the detector components themselves- unless it is cooled down. Liquid nitrogen is the cheapest way to do this.

2. Gas separation. Water and carbon dioxide are two commonly studied fluid phases in geology. Studying them often involves separating them from air or other combustion gasses. Dry ice/ethanol slurries are cold enough to condense water, and liquid nitrogen condenses CO2. so you stick various parts of your gas line in buckets of those substances, and they freeze out for later analysis. These are called cold traps.

3. Gas purification. Sometimes, instead of condensing a gas for analysis, you simply want to remove it. For example, the excimer laser that I used to keep running used a gas mixture of fluorine, argon, and helium. Invariably, water would contaminate the gas reservoir, reacting with the fluorine to form HF and oxygen. The oxygen is no big deal, but the HF prevents the formation of excited dimmers that actually produce the laser light. Since HF is polar, it condenses much more easily than the other gasses, so we use liquid nitrogen to freeze it out. In that case, though, the gas is in a continuous flow, and you can’t let it get too cold or the argon might condense as well. For all you former students reading, this is why I get so pissed off when you guys let that cold trap run dry- if the coil warms up, then the entire 3 months worth of HF gets back into the gas stream and fucks up the electrodes when you activate the trigger.

4. Some solid state charged particle detectors, like the EDS system on the microprobe, also like to run at low temperatures. But I don’t know the exact reason for that.

5. Dry gas. Some of the liquid nitrogen in storage will inevitably boil off in storage as a result of imperfect insulation. This gas is moderately pure, but very dry, and thus is handy for things like venting vacuum systems, flushing furnaces, dusting shit off, and other random tasks that require low pressure, low oxygen, and/or dry gas.

How about y’all?

Tuesday, October 21, 2008

For whom should I vote?

My initial predilection for McCain has been approximately offset by his terrible campaign and VP choice. Senate is an easy R, and house is an easy D this year (will post endorsements this week), but not sure on Pres.

Anyone willing to try to influence a moderate, fiscally conservative Republican voter is welcome to post in comments.

I should point out, however, that either candidate would probably be the best president of the last 20 years, to it's a good kind of confusion.

Monday, October 20, 2008

LOL dunes

One of the things I least like about the climate change discourse in our society is the shrillness of the doom and gloom that surrounds the arguments for urgent action. For one thing, the environmental over does doom and gloom, to the point where our doom-o-meters get saturated and we no longer care. But more importantly, it shows an intellectual laziness that perturbs me. I mean really, emphasizing the negative aspects of the collapse of civilization is just so easy. It requires no consideration, no creativity. I think it would be far more impressive to detail the comforting aspects, the positive slants, and even the humor inherent in agricultural society crumbling into dust.
Take desertification, for example. Surely there is some cheap joke that can be devised about sand dunes rolling into former pastureland. After all, a longitudinal dune isn’t going to stop at a cheeseburger- it will consume the whole ranch. And what better way to illustrate this than a LOL dune:

This longitudinal dune is prograding north from the Simpson Desert in far western Queensland, and is currently in the process of burying the stockyard shown above. It is a bit too slow to eat any beef, however. The station stopped running cattle in 2003, and the land was sold off as a nature reserve. These days, only camels, kangaroos, and reptiles live out here.

Saturday, October 18, 2008

Carbon sequestration- the basics

Our civilization is currently putting dangerous amounts of carbon dioxide into the Earth’s atmosphere. People are finally starting to realize this, and are looking for ways to reduce the impact as painlessly as possible. One way to do this is to bury some of carbon dioxide that we produce, so that it can’t reach the atmosphere or shallow ocean. While this is a valid and sensible thing to try, the process is often poorly understood or misrepresented. So I’ll run through some of the basics.

Firstly, carbon dioxide is poisonous. We all exhale this gas, so those sorts of levels obviously aren’t going to do us too much harm, but percent levels will, and very high levels can displace air, leading to asphyxiation. In 1986, carbon dioxide dissolved in an African lake uncontrollably exolved, and the resulting cloud of CO2 gas killed 1800 people. The annual human production of carbon dioxide is about four million times larger that the flux of CO2 into that lake, so sequestering CO2 poorly could be extremely dangerous to a very large number of people.

CO2 is also acidic when dissolved in water, and can be quite reactive in certain geological environments. So you can’t just stash the stuff any old place, or it might escape and kill somebody.

Secondly, once CO2 is mixed in with other gasses, it requires energy to extract and purify it. So sequestering CO2 from a reaction that produces pure gas will be more efficient that removing CO2 from combustion exhaust, or from the atmosphere.

Thirdly, CO2 is 3.6 times heavier than the carbon was before it was combusted. So transport costs for CO2 will generally be even greater than they were for fuel.

So, what does this tell us?

If we want to sequester carbon efficiently, the best way to do so is sequestering pure CO2 from a factory that is located very close to the sequestration site.

One potential site for storing CO2 is old oil and gas fields. This is sensible, at least at first pass, since the presence of hydrocarbons in a reservoir requires some sort of trapping mechanism. Mineral sequestration is something I mentioned a while back, but it is still in the research phase at this point.

So, if you build a chemical plant (say a plastic factory) at an oil wellhead, injecting the CO2 back into that reservoir is pretty close to the ideal environment for sequestration, as long as the volume of CO2 produced is less than the volume of oil extracted. Since oil has a greater carbon density than CO2, you need to be leaving some of the carbon in some other form (like plastic) for this to work.

Similarly, if you identify as suitable large, safe reservoir for sequestration, building a cement plant or smelter nearby will give fairly pure CO2 which can then be sequestered without too much trouble.

Another sensible carbon sequestration plan would be to build a gas based power plant at the well head for a natural gas field, and then sequester the CO2 extracted from the exhaust. Methane and CO2 both contain one carbon per mole, and they are both gasses, so the CO2 volume produced should be similar to the volume of methane burned. Because CO2 is more compressible, you might even gain some space, but this could be negated if subsidence over the gas field reduces the available volume for sequestration. In this situation, you still need to separate the exhaust gasses, but the transport and sequestration problems are minimized.

So what about CO2 from coal-fired power stations? Well, that CO2 is a combustion product, so separation is required. Unlike gas and oil, coal extraction does not leave a potentially useful reservoir behind- it just makes a big hole in the ground. So safe, large storage areas will need to be found, and the CO2 will then have to be transported to the sequestration site.

Thus, it is likely that sequestering CO2 from coal combustion will be more expensive than sequestering it from other industrial processes, or from natural gas-based electricity production.

This is an important point.

Often, carbon sequestration is only mentioned in the context of “clean coal”. But if we want to sequester CO2 efficiently, we are better off doing it for non-coal CO2 sources first, as they are likely to be easier and more efficient.

As a result, it would be a very serious mistake to allow coal companies to control carbon sequestration technologies, especially if they are funded by the public. Because limiting sequestration to only that CO2 produced from coal combustion makes the process less efficient, and therefore more expensive.

The space carnival has the biggest tent this election

Here on Earth, the medial political grouping on the northern continent of the western hemisphere is preparing for an election. The the election culture of this particular nation, it is common to refer to having a 'big tent' when wooing potential voters. Of course, tents are conspicuously absent on the campaign trail, and the biggest tents are actually found at circuses and carnivals such as this.

Because this is a space carnival, our tents should be very large indeed.

Our first carnival tent encompasses the planet Earth, that six million, million, billion ton ball of rock and molten iron that we all know and love. Evidently, not everyone on this planet is in a big tent sort of mood, as NASA has canned Conference Travel in 2009. Despite this small minded view, at least some folks are looking for the big picture. plans for big telescopes have been described in a round up of future giant telescope news, which has also been described from a historical perspective, as Newton was on to this trick ages ago.
As large rocks such as the Earth inevitably end up becoming targets for smaller, jealous rocks, there has been some discussion of death by meteorite. And the fall location of the meteorite that landed last week was plotted up, just in case Anyone likes collecting meteorites.
We also have an excellent description of the Earth’s Wobble, or Precession. And for those who like to push the tent's edges, there's a
suborbital rocket experiment carrying a payload from Kentucky

Our second tent encompasses the Earth's Hill sphere, and everything in orbit around our home rock.

Although this picture only shows our largest natural satellite, there is news from the biggest artificial one as well. Educators have released Teacher Tools for the High Frontier: International Space Station. And there has been much made of the story of an Astronaut's son, who recently boarded the ISS as a Russian tourist.
On the less commercial, more nationalistic side of things, the idea that China faked its space walk is debunked here. And the ESA is readying a satellite to Study the Earth's Gravitational Field. Finally, the US Vision for Space Exploration has released a publicity video touting systems that hopefully will be built in our lifetimes.

Moving out, we can put the inner solar system under a tent that is a mere billion km wide.

We start On Mars.... Phoenix has won an award as a World-Changing Innovations of the Year. And futuristic probes like ExoFlys are also discussed.
Asteroids are especially interesting if they arrive on your doorstep, and
Pallas is highlighted at the Planetary Society's blog.

The Outer solar system tent is substantially larger- 60 AU across will net Neptune, but we'll need something ten thousand times that size to capture the Oort cloud.

In the icy regions of the outer solar system, a comet discovered from an icy region of the Earth is celebrated.The presence of water volcanoes on Enceladus has some folks doubting the laws of physics. There was a brilliant 5 day liveblog of the DPS meeting held last week. Day 2 was on Rings, Titan, Comets, and orbits. Day three consisted of More Titan, and exoplanets. While day five was icy and not-so-icy moons. Finally, there is a report on new data investigating Holmes, the exploding comet.

Expanding our tent to a few hundred thousand light years keeps the Milky Way out of the rain.

Lack of rain is good for observers of variable stars, one of whom recently had an almost perfect night. Some other stars in our galaxy host planets, and the main detection methods for finding them are summarized here. Of course, telescopes are rarely point and shoot- it is common for observers to have challenges and puzzles. Anyone familiar with the moons of Jupiter knows a bit about tidal heating, so it is only natural for this effect to be considered for the habitability of exoplanets. And just in case some of those planets are inhabited with technologically advanced internet addicts, Bebo has beamed a friend invite into space. Going back to the DPS liveblog, day one involed Mars, exoplanets, defining planets and Enceladus.

The ultimate big tent experience involves covering the entire universe with rain resistant canvass.

Not only does this involve an enormous amount of fabric, but it also raises interesting philosophical questions about what you peg the guy lines to. Fortunately, we have an explanation of why dark matter is more diffuse than ordinary matter to make this subject a little less mysterious. And cosmology has evidently also inspired jazz. Obviously, accessing the distant reaches of the universe is neigh impossible with known science, but that won't stop people's imaginations from blasting out there at “Warp 10, Scotty!”.

Friday, October 17, 2008

Absentee ballot question for expats

I haven't received my ballot yet. Have you guys? If so, where are you and when did it show up? And where is it coming from? Is anyone else still waiting?

Sunday, October 12, 2008

Anyone like collecting meteorites?

On Friday, Emily at the Planetary Society's blog posted satellite images of the fireball from the ex-asteroid that crashed into the Axis of Evil last week. Luckily, that image had grid lines on it, so I imported it into Google Earth and plotted up the location.

While a large proportion of the impactor vaporized, I would be very surprised if a few kilos didn't reach the ground. There might even be a ton or two. And it turns out that the site is close to a road, in very open country. Of course, given the low angle of impact, the debris may be significantly farther east. But that's OK- that puts it even closer to the road. Anyone out there have a Sudanese drivers license and a Landcruiser in NE Africa? That road doesn't look real good, but it may be further west than the yellow line, based on the (low res) photos.

Friday, October 10, 2008

Charitable linkage

Firstly, this week's space carnival is live from Kentucky. More importantly, the talented Maria Brumm is representing geology in this year's Donor's Choose Challenge. Show that our hearts of stone are more generous than those of the physics, mathematical, and biomedical communities. Head over to her place, and please give generously.

Thursday, October 09, 2008

Nebular nonsense or neat knowledge?

Last week we talked about Gounelle & Meibrot's astrophysical nay-saying with regards to the origin of short-lived nuclides. As I pointed out, one of the long standing problems in this field is that cosmochemists and astronomers don’t often talk to each other. Just before I left the ANU for work in the real world, the planetary science institute started holding occasional lunchtime seminars to address this issue. The seem to still be cruising along. I’ve been attending when I’m in town, and that’s the origin of the reading list for these papers I’ve been blogging.
The seminars themselves have been a mixed bag. They are really good when folks from one discipline or the other nicely fill in blanks in the other group’s knowledge set. But there have also been some where older, less patient faculty have wasted everyone else’s time by talking past each other instead of letting the rest of the group actually learn.
Luckily, here I can type uninterrupted to you guys, and simple direct any interjectory comments into the spambot. Hester & Desch look at star formation in the same astronomical setting as Gounelle & Meibrot did, but with an observational, rather than a numerical approach. H&D is actually an earlier paper, and is referenced in G&M, but in ways that I don’t actually understand.
Basically, H&D look at the distribution of dust, accretion disks, new stars, and “blister zones” where the radiation from big stars has blasted a hole in the surrounding dust. One thing I don’t understand is why they refer to ionized hydrogen as “H II”, since hydrogen only has one electron to lose- is this obscure, counter-intuitive astrospeak?
Anyway, there are two main points that H&D make. The first is that as the blister zone expands around a big, hot, young star, it creates a shock front which can induce star formation. So instead of all stars forming at once, there is a sort of stellar domino effect.
The other big point was that the radiation effect from the nearby big stars on the accretion disk dynamics was often more important than the radiation from the star at the center of the disk. This, of course, has the implication that modeling accretion in an isolated heliocentric system might give incorrect results, if the main radiative forcing is actually external.
What I don’t get is how G&M arrived at the opposite conclusion, when they state that:
“It is thus assumed that the massive star, which evolved into a SN, and the protoplanetary disk were coeval and formed in the same stellar cluster (e.g., Hester & Desch 2005).
Yet the whole point of the H&D paper is that the star formation is NOT coeval, as small star formation is induced by the radiative pressure from big stars on the cloud. G&M don’t seem to even acknowledge, much less address this point. Instead they use rapidly decreasing linear star formation models, in which the youngest small stars are already several million years old by the time the first supernova goes off.
Anyway, I’m a geologist, not an astronomer, so maybe someone knowledgeable- like the blogospheric queen of galactic star formation, can point out what I’ve missed. But even if this entire post reads like scientific gibberish, I still recommend having a look at the Hester & Desch paper. It has lots of pretty Hubble Space Telescope pictures in it.

J. J. Hester & S. J. Desch 2005 Understanding our origins: Star formation in H II Region Environments. Chondrites and the protoplanetary disk ASP conference series, Vol 341. A. N. Krot, E. R. D. Scott, & B. Reipurth, eds.

Wednesday, October 08, 2008

Head of Skate

A few weeks back, actor Matt Damon compared the nomination of Governor Palin to a bad Disney movie. Evidently, there is now a trailer.

Monday, October 06, 2008

Mercury fly-by

If all went well, the Messenger spacecraft is 50 minutes past closest approach of its second flyby, and is currently 20,000 km above the fastest planet and receding rapidly. The spacecraft has turned away from Earth to perform its mission, so it will be another 19 hours before contact with the spacecraft is regained. I wonder if anyone on the mission will manage to get any sleep during that time. Here is the penultimate approach picture taken before the spacecraft turned away:

Camels in the outback

When I first came to Australia, I had heard all about kangaroos and emus and platypuses and all these queer and wondrous organisms that inhabit this continent. But it wasn’t until I actually took my first road trip into the wide open spaces that I learned about Australian camels. We didn’t actually see any that trip, but they’re still out there- over a million of them, by some estimates- and this last trip I finally managed to spot a decent mob- a breeding group with a cantankerous old bull, as many cows as he can handle, and all sorts of little youngsters.
Camels, of course, are not native. As the Wikipedia article explains, they were introduced in the late 19th and early 20th centuries, after a number of disastrous expeditions proved that the interior of the continent was inhospitable for other beasts of burden. By the 1930’s, the automobile had made camels obsolete as a mode of transport, so most of them were abandoned- left all alone in a continent whose arid conditions suited them perfectly. Their current range exceeds that shown in this Environment Australia fact sheet (pdf).
Australia has a long and dismal history of invasive species, but by the standard of the cane toad or the rabbit, camels are relatively benign. Conservation theory is further complicated by the fact that dromedary camels are extinct in their native range. All 14 million old world dromedaries are domesticated (There are a few wild Bactrian camels in east central Asia). If you want to see wild dromedaries, Australia is the only place where you can do so. As a result, all sorts of crazy research on their physiology and behavior is done here (e.g. During the rutting season, Bulls become hypothermic overnight so that the exertion of rutting the next day doesn’t overheat them).
One theory as to why they aren’t a disaster is that they fill the niche of browsing megafauna that was left vacant when Diprotodon and other large animals were exterminated when the continent was first inhabited. So all the creatures that would have been outcompeted by camels are already dead.

However, they have no natural predators (although cattlemen shoot them on sight), and the herd is growing at an estimated 10% each year, so aerial hunting and other control measures have recently been started. While some wild camels are recaptured to sell back to the old world, the economically viable take is not nearly enough to hold the population in check. Which is a bit of a waste, really, because camel meat is delicious. The low fat content makes it easy to cook badly, as it easily overcooks and dries out, but a well done camel curry is to die for.

Wednesday, October 01, 2008

How astrophysicists spoil cosmochemical parties

ResearchBlogging.orgAs 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.


The Astrophysical Journal

Monday, September 29, 2008

Accretionary wedge and more

Geology in space, the 13th repeat of the Accretionary wedge, is up at goodschist. In addition, has a large collection of geoblogs listed. So go read their stuff.

How to arm Bridezilla

A couple of years ago, (which is an epoch on blog timescales), Jen over a cocktail party physics blogged about diamonds, gold, and other constituent materials of engagement rings. Since I did my PhD on diamonds, we had a bit of a discussion on the subject. Not long afterwards, her cat evidently lost said ring, generating predictable distress.

Since Jen is a journalist, and Sean is a theoretician, I planned a blog entry describing a variety of non-destructive analytical techniques which they could use to find said article of jewelry. This way, should one of them go Bridezilla (or Groomzilla), they would have a variety of caustic, ionizing, and nuclear tools at their disposal. Unfortunately, said post languished in my half baked finished box for the better part of a Wilson cycle. However, as today is their wedding anniversary, I figured I might excavate it, dust it off, and post. So without further ado:

Engaging ways of finding a ring

The following analytical techniques are standard geochemical techniques that have been used to analyse diamond and/or gold by various scientists over the years. Destructive techniques, though generally more effective, have been excluded from this list. Each method consists of a short description of how it works, and summary of the experimental setup you will need, and a brief description of what the side effects might be for the cat. They are listed in increasing order of impracticality.

Xray induced optical fluorescence

Theory: Most diamonds fluoresce in the optical wavelengths when illuminated by X-rays, as a result of impurities and structural defects. In fact, this technique is usually what is used to recover the diamonds from the kimberlite ore in the first place. The ground ore is illuminated with X-rays, and anything that glows is retrieved (all in a highly automated process).

Method: Black out apartment. Irradiate everything in it with X-rays. Grab anything that glows.

Effect on cat: increased cancer risk from moderate X-ray dosage.

X-Ray fluorescence

High energy X-rays will knock inner shell electrons out of the atom. When outer shell electrons fall down to fill the vacant shell, an X-ray is emitted. These X-rays can be detected with an X-ray spectrometer, which will identify the element being irradiated. Since most apartments don’t have a lot of gold lying around, looking for Au K , L, and M band X-rays will detect the gold instead of the diamond. Better yet, the K and L X-rays are quite energetic, so if the ring is obscured by a low Z number object (like a cat), they may be able to penetrate it.

Method: as above, but with a high energy, brighter source (Is there a synchrotron in your block of flats?).

Effect on cat: Chronic radiation damage, but with a higher dose.

Gravimetric/ magnetic separation

Theory: Diamonds and gold are both denser than wood, plastic, concrete, and most other building and furnishing materials. Unlike steel, they are not ferromagnetic. So a gravimetric and magnetic separation should reveal the ring.

Method: grind apartment into gravel-sized bits. Use a magnet to pull out any steel. Dump the remains in a heavy liquid (a variety of iodine or bromine organic molecules are available for this purpose) which will float the concrete (as well as plastics and wood) Your ring should sink and be recoverable.

Effect on cat: The grinding step may produce physical damage. In addition, most heavy liquids are extremely toxic.

Acid dissolution

Theory: diamond and gold are both very insoluble in most caustic liquids. Dissolving the apartment with increasingly aggressive solvents should leave the ring untouched.

Method: dissolve plastics in the appropriate organic solvents. Dissolve wood in this stuff. Dissolve concrete, ferrous, and base metals in sulphuric acid.

Effect on cat: Ends up in a solution of the fairly final variety.

Mössbauer Spectrometry

Theory:197Au, the only stable isotope of gold, has an excited isomer which decays back into the stable isotope with a half life of 7 seconds. By irradiating stable gold with gamma radiation of the exact energy required (about 400 KeV), a nuclear transition to the excited state can be induced. This will then decay with the same characteristic energy, which can be detected with a gamma ray spectrometer.

Method: Irradiate the flat with gamma rays of the appropriate energy to excite the Au nucleus. Then switch on your GRS and home in on the emitter.

Effect on cat: Gamma ray irradiation is similar to X-ray damage described above, but potentially more penetrating.


Theory: Proton-Induced X-ray Emission. This is similar to XRF, except that high energy protons are used instead of X-rays. The disadvantage is that you need a particle accelerator- nothing LHC sized,as a few MeV is the energy most commonly used. The advantage is that proton beams can be focused better than X-rays, allowing you to target your search more carefully.

Method: Remove an elevator and install a particle accelerator in shaft. Evacuate apartment. Raster beam across all potential hiding places, and use an X-ray detector to spot emission from inner shell ejection of electrons from the gold atoms.

Effect on cat: death by asphyxiation. Potential additional radiation damage from proton beam.

Neutron activation

Theory: 197Au will fairly easily absorb a neutron, transforming to the radioactive isotope 198Au. This isotope decays so 198Hg with a half-life of a couple of days, releasing a characteristic gamma ray in the process. Both neutrons and gamma rays can easily penetrate all but the best shielded of hiding places, making this method ideal. Note that only a tiny fraction of the gold atoms are transmuted, so the mercury toxicity threat and loss of gold from the ring are both minimal.

Method: Construct an unshielded nuclear pile in your living room. Flood flat with neutrons. Afterwards, send in a radiation-shielded robot with a gamma ray spectrometer to detect 198Au decays. The apartment (and most of the building) will be uninhabitable for a few decades due to the production of radioactive elements, but the ring will only be too hot to handle for a month or so.

Effect on Cat: Death from acute radiation poisoning.

So there you have it. Jen, Sean: Happy anniversary. And just remember, if you ever need to find anything, science is always on your side.

Saturday, September 27, 2008

Carnival of space #72

Is live over at twisted physics.

Thursday, September 25, 2008

Always use pencil

Write-in-the-rain notebooks are of dubious utility when used with water soluble ink...

Of course, waterproof ink in not necessarily a good defense. When I was a student, I once had a technician use my lab book to smother an ethanol fire. The fire went out, and the notebook even soaked up the residue, neatly removing the hazard. Trouble is, there aren’t many inks that aren’t soluble in ethanol. While the chromatography patterns were awesome, reconstructing my work for the past month was a bit of an effort. The nice thing about graphite is that it is insoluble in anything that doesn’t attack paper.

Tuesday, September 23, 2008

The Earth Science President

Which Presidential candidate is best for Earth scientists? I’ll briefly have a look at some issues, then let y’all discuss. Please note that this is an autopost that I actually types up 2 weeks ago; so if something interesting happened since the Republican convention, it will not be considered.

Issue one- Resource extraction.
The Republicans seem to be considerably more gung-ho about exploring for and developing mineral and energy resources. The Democrats are considerably less enthusiastic about domestic fossil fuel production. In addition, Palin strongly supported infrastructure projects like pipelines which are crucial for developing small and medium sized deposits.
McCain wins this category.

Issue two- Regulation
Good regulation can actually benefit Earth scientists. While mining certainly employs geoscientists, reclamation, remediation, and water monitoring also provide good jobs for us, provided the regulatory environment creates a need for their skills. On the other hand, bad regulation can stop a project from progressing at all, or provoke a company into hiring lawyers to fight the regulations, instead of using earth scientists to follow them. I suspect that the Democrats would impose more stringent regulations, but I don’t see the evidence that their regulatory regime would be constroctive, rather than obstructive.
McCain wins again

Issue three- Education and research
Obama has promised substantial increases in federal funding for schools, college students, and research funding. While it is not clear if his research funding increases would proportionally increase Earth sciences relative to other fields, I suspect that there would be at least some improvement. In contract, the Republicans promise mostly to cut “wasteful” spending. In addition, the Republican VP is on record opposing evolution in schools. Since evolution is important keystone of geology, I can see a situation where the Republicans authorize drilling for everywhere, only to find that there are not enough qualified geologists around to site the holes.
Obama wins this one.

Issue four- Economy
The current high prices for most mineral resources is a direct consequence of rapid economic development in Asia, principally China and India. In recent months, there have been signs that the deteriorating US economic position is starting to effect growth all over the world. So strong US leadership is useful for maintaining worldwide growth to support prices. The Republican economic plan doesn’t seem particularly sound, as it continues expensive tax cuts and military programs without any obvious spending cuts of similar magnitude. While the democrats have a large number of spending proposals, I feel that their overall economic vision and ability is probably stronger.
Obama wins again.
If anyone can think of a tiebreaker issue, post it in comments. Please frame all comments as what is best for geology and its practitioners, however. While I acknowledge that people may vote for reasons unrelated to their profession, there are about a billion other blogs that are discussing that issue already.

Saturday, September 20, 2008

I’d like to thank the alaskademy

It looks like the generous allochthonous Alaskan who blogs as Wayfarer Scientista has given me the Brilliante award. Presumably, this is some sort of baddeleyite allotrope.

Baddeleyite, formula unit ZrO2, is a great mineral, so it is a shame that synthetic cubic zirconia has a higher profile in the more colorful parts of non-geologic human culture. Of course, the trick to getting ZrO2 to grow in a cubic structure is itself interesting- it seems that cubic zirconia is in fact a Zr-rich tazheranite solid solution. But growing big crystals at all is impressive when you consider that zirconia has one of the highest melting points of any known substance. But enough of this lapidarial digression.

In order to crystallize baddeleyite, two conditions must be met. Firstly, the major minerals must be saturated in Zr. Secondly, the SiO2 activity has to be low enough that zircon doesn’t grow. This makes the mineral somewhat uncommon. Never the less, it does have a high U/Pb ratio, so it is used for geochronology for rocks that don’t have zircon.

Interestingly, metamorphic fluids are often silica rich, so in some altered rocks a zircon reaction rim will grow on a baddeleyite, allowing both the crystallization age and the alteration age to be determined. In practical terms, this means that if you want a good date, then natural, monoclinic zirconia is more reliable than its artificial, cubic allotrope.

Evidently I am supposed to pass this award along, so nominate the following blogs as being cubic zirconia-worthy:
The Planetary Society Blog
Molecule of the Day
This non-American Life
Apparent Dip
The Volcanism blog
All my faults are stress related
And if any of y'all have already been awarded, then give yourselves an allotrope instead.

Tuesday, September 16, 2008

Isotope Park

When it comes to extinctions, animals are extremely over-represented in the public eye. Everybody knows what a dinosaur is. And most people have heard of trilobites. But seed ferns? Not so much. And when it comes to nuclides, the lack of public recognition is even more severe. When’s the last time your non-geological friends told you their 6 year old loves 60Fe?

I would like to correct this. Extinct nuclides are vital to our understanding of the solar system, and are every bit as deserving of popularity as a triceratops. I consider this to be an injustice, a disgrace. I will not be satisfied until Hollywood blockbusters have Laura Dern fleeing in terror, as a pack of angry- and radioactive- molecules of 26Al129I3 come chasing in pursuit.

But before this dream can become a reality, I should probably explain what they are.

Extinct nuclides are radioactive isotopes that no longer exist in detectable quantities in the modern solar system, but whose presence in the early solar system can be deduced from their decay products. A table showing several geologically interesting live and extinct isotopes is shown below, with a logarithmic timescale at top.

Extinct nuclides are valuable for establishing timelines for the first 1-50 million years of the solar system’s history. This is the time during which the protoplanetary disk cools enough to start condensing crystalline matter, and this matter then forms condrules, asteroids, planetesimals, and eventually, the terrestrial planets that we know and love today. It is constrains from these isotopic systems that tell us the chondrites and apparent bodies for iron meteorites formed in the first few million years, while the time required for these planetesimals to collide and form the four inner planets was about ten times as long. This is all a result of painstaking isotopic analysis and interpretation using a fairly simple theory. The story goes like this:

Once upon a time, there was a giant molecular cloud. One day, a nearby star exploded in a supernova. This supernova created lots of R-process and P-process nuclides, including all the short lived ones. The shockwave triggered a collapse of the molecular cloud, and initiated the formation of the sun and the rest of the solar system, with all these newly formed nuclides mixed in. The radioactive ones decayed, but the stable ones lived happily ever after.

At least, that’s what we geochemists thought. Unfortunately for us, a gang of tactless astrophysicists crashed our storytime party and spewed numerical garbage all over our tidy white cleanrooms. But that is a discussion for another day.