Cosmochemistry treasure trove

While looking for a good online Pb isotope evolution curve, I stumbled across the Planetary Science Research Discoveries site. It is an archive of popular science explanations of research papers in the planetary science and cosmochemistry field.

I've read a bunch of these articles, and they are brilliant. This is great, because I've been wanting to summarize some of these topics, but now I have found that people much more eloquent that I have already done so. All I need to do is link them.

So, here are some lovely writeup on:
Dating the earliest solar system condensates
Galactic migration and presolar grains
Gas giant migration hypothesis for the late heavy bombardment

I'm happy to field questions about any of these, although my ability to answer questions about orbital modelling is fairly limited.

Disclaimer: Geoff Taylor has collaborated with the scientists I work for and has visited our lab. None of these articles relate to that research.

Gang Gangs and Sweetgums

Disclaimer- this was the post I was working on before Mrs. Lemming went into labor. I apologize for any change of tone halfway through. But seeing how she was attacked by lawyers this week, I’m gonna dedicate this post to the writer of Retrospectacle. Ms. Shelley Batts, this parrot’s for you.

The American sweetgum (liquidambar styraciflua) is a deciduous coastal plain tree that grows from around New York City down the Atlantic seaboard well into the Deep South. It is notorious for its sweet gum balls, which are spiky, hard, inch-sized fruit which are painful underfoot and remarkably resistant to rot, predation, conflagration, or any other means of destruction. We had a big sweet gum tree in the house where I grew up, and after raking them into the compost heap, we could find layers where they would remain years after everything else rotted away. If not raked up, they would inevitably get frozen into the dog’s fur in winter, or get picked up by the lawnmower and accelerated (undamaged, of course), into my shins. It was a family joke that they were so indestructible that after the sun burned out and blasted the Earth’s atmosphere and biota to a crisp, the sweetgum balls would remain, the only biological object refactory enough to survive the inferno and bear testament to the former presence of life on the planet.

Of course, that was an American view of the balls. Here in Australia, they are considered bird candy.



Liquidambar (as they are locally known, to differentiate them from eucalypt “gum” trees) are a relatively common decorative tree planted in Victoria, southern NSW, and here in Canberra. And as this picture above shows (taken by me, with my own camera, not borrowed from any journal via the fair use provision), gang gangs love to eat sweet gum balls.

Unlike sulphur crested cockatoos or galahs, gang gangs are not well adapted to agriculture. They don’t flock to developed areas, and they avoid human contact. Unlike most parrots, I’ve never seen them eat any nuts, birdfood, or fruit. But every autumn, as the foreign deciduous leaves fall and reveal the sweetgum balls, gang gangs fly in from the surrounding native forests to feast on the most indestructible seed pod North American trees have to offer.

Possible terrestrial planet around Gliese 581

The European Southern Observatory has released a press release claiming to have found a possible terrestrial planet in the habitable zone around the red dwarf Gliese 581.

Rampant speculation has ensued.

I’ll give the facts as I see them, but since I’m not an astronomer I may need to be corrected.

The radial acceleration method measures the pull exerted on the host star by an orbiting planet. These measurements can be done extremely precisely. Since they rely on the law of gravitation, they can detect smaller masses if you have a small star and a close planet.

The wobble that is detected gives the orbital period (which, given the mass of the star, yields the orbital distance), and the amplitude, which is dependent on the mass of the planet and the geometric configuration.

The reported mass is a minimum mass- that is, it is the mass if, from the exoplanet’s POV, our sun lies in the plane of that exoplanet’s ecliptic. Otherwise, the actual mass is greater than this minimum mass by 1/cos X, where X is the angle between our sun and their ecliptic. Fancy spherical geometry* thus suggests that the actual mass is unlikely to be more than 30% higher than the minimum mass.

So this new exoplanet probably has an actual mass between 5.5 and 7 or so Earth masses.

The mass, and the orbital period are all we can actually determine at this point in time.

There have been reports of a planetary radius. As far as I can tell, these assume a terrestrial (or icy) composition, with a little bit of gravitational self-compression thrown in.

Obviously, such assumptions are speculative- the terrestrial planets in our own system don’t even have the same bulk composition as each other. Neither do the icy moons.

The presence or absence of water is also speculative. It is worth noting, however, that on Earth, most of the water is believed to have been added late in planetary formation. The late veneer hypothesis suggests that volatiles and highly siderophile elements were added to the Earth late in its formation from impacts of outer solar system objects. While our solar system has several gas giants to gravitationally deflect bodies inwards, no such giant planets exist in the Gliese 581 system outward of planet c (planet b is only 8 earth masses- compared to 318 earth masses for Jupiter).

Additionally, spectroscopic attempts to identify water in other exoplanet- the hot jupiters HD 209458 and HD 189733- failed to identify water in the atmosphere of either planet. This is despite theorists claiming that it had to be there.

Of course, an unusual result shouldn’t be surprising. Ever since we went to the moon, the rule of thumb for planetary exploration is that they have been stranger than anything we could hypothesize. So my guess is that Gliese 581c will adhere to this rule.

At the moment, all we can do is guess about this planet’s composition. But hopefully, the Terrestrial Planet Finder (recently bloged at green gabbro), if funded, will be able to image it, and determine the IR spectra. The key fact about this new discovery is that if the TPF gets flown, it now has one definite target to analyze. And since the signal for this planet was 3 times the LOD, hopefully more will follow.

Of course, if there is anyone living there, and they look out towards the galactic rim, this is what they will see:

Orion is to the left, the Pleadies are to the right, and somewhere in this picture is our sun. Can you find it?

* I've only estimated this, feel free to quantitatively set me straight.

Nappy lab

I am currently on a two week unpaid sabbatical known as “paternity leave”. The purpose of this break is to keep Mrs. Lemming sane and happy, and one of the major components is addressing the nappy question.


Above are the various options available. There is the basic cloth nappy, the disposable nappy, and the hi-tech eco-yuppy excrement management system that got sent to us from the US. It is my job to experimentally determine the best use for all of our shit-stopping assets before I go back to work. If anyone’s interested, I can do a more extensive description of the bonuses or deficiencies of each, possibly including some semi-quantitative data. Or, I can get cracking on the lead isotopic evolution post. Any requests?

Conservative reply to Sciencewoman

I admire Sciencewoman’s ability as a scientist, her honest in blogging, and her generosity in sharing her work / motherhood juggle under difficult circumstances. However, I suspect that we disagree on politics. She recently posted pictures of baby clothes in support of the pro-censorship group Momsrising, whose philosophy seems to include teaching their daughters that the correct response to having their feelings hurt is to get the offender fired.

In the interest of expressing diverse political viewpoints between science bloggers, here is my response.


Note that I used computer effects, since I can’t afford to politicize my daughter’s entire wardrobe.

Disjoint, sleep-deprived comments

Sean has a nice post at cosmic variance on the difference between science and math.

Thermochronic has talked a bit more about the politics of reviews. I have news as well. Last Monday, I was asked to review a paper. On Tuesday, I got the paper. On Wednesday, Mrs. Lemming went into labor, and I haven’t glanced at anything but the “please complete by” date since.

So I don’t really know what I am going to say yet, but I think I’ll sign it. One the one hand, I don’t like advocating actions I’m not willing to take. Also, as a technician, I don’t live and die by the whims of publishing. I’m actually paid to keep machines running and samples processed. If I end up on the blacklist of an infamous Topeka ubergeologist, it doesn’t really effect my job performance.

Mostly, though, my experience in science is that I’ve never gotten anywhere simply by not stuffing up. All of my jobs, degree acceptances, etc. have come from taking a gamble and pulling something just a little bit crazy off. I’ve never gotten anywhere via the normal channels. So at this point in my career, rattling cages, taking risks, and stirring pots is second nature to me.

Sciencewoman is the amazing researcher/ mother. See her posts on taking a baby to the field and seminars.

I just finished my contribution to a paper during the little one's nap. This is the data reduction/writeup that I was going to do last Wednesday evening.

Chronology of evil media empires: does anyone know how many hours passed between NBC firing Imus and then airing the psychopath tapes? We don’t get that much American news over here, and I’ve been preoccupied. But I'm disgusted enough to trade any NBC shares I might own in for part of some tobacco company.

There were a couple of other really good science blog posts last week while we were in hospital, but I can’t remember where. Any tips/ suggestions?

Australian culinary secrets revealed!

Consider this my Frink Tank tribute:



For those who don’t get it:

If you don’t know what vegemite is, hang out with more Australians; it is a cultural subtlety not learnable from a book.

If you don’t know what meconium is, look it up on the web.

If you don’t know what the white soiled bit of fabric is, you need to spend less time in disposable, consumerist culture.

If you understand all of this, but still aren’t amused, that just means that you have taste. If that is the case, stay away from vegemite.

Our baby likes dinosaurs

Take a close look at the print on her jumpsuit. And that, my friends, is about as close as we are going to get to geology this week. I hope to post on the lead isotopic evolution of the Earth soon- it is timely, as lead isotopes are used for studying pregnancy and lactation.

But I need to review a paper and write my section of another and prepare a talk for next month. And then there’s the nappies and bellytime and snuggles.

LLLL is one week old today.