An international team of scientists led by researchers at the University of Hawaii at Manoa have found no evidence supporting an extraterrestrial impact event at the onset of the Younger Dryas ~13000 years ago.
The Younger Dryas is an abrupt cooling event in Earth’s history. It coincided with the extinction of many large mammals including the woolly mammoth, the saber toothed jaguar and many sloths. This cooling period is generally considered to be the result of the complex global climate system, possibly spurred on by a reduction or slowdown of the thermohaline circulation in North America. This paradigm was challenged two years ago by a group of researchers that reported finding high iridium concentrations in terrestrial sediments dated during this time period, which led them to theorise that an impact event was instead the instigator of this climate shift. A team led by François Paquay, a Doctoral graduate student in the Department of Geology and Geophysics at the University of Hawaii at Manoa (UHM) decided to also investigate this theory, to add more evidence to what they considered a conceptually appealing theory. However, not only were they unable to replicate the results found by the other researchers, but additional lines of evidence failed to support an impact theory for the onset of the Younger Dryas. Their results will be published in the December 7th early online edition of the prestigious journal the Proceedings of the National Academy of Sciences.
The idea that an impact event may have been the instigator for this cooling period was appealing because of several alleged impact markers, especially the high iridium concentrations that the previous team reported. However, it is difficult for proponents of this theory to explain why no impact crater of this age is known. “There is a black mat layer across North America which is correlated to the Younger Dryas climatic shift seen in Greenland ice cores dated at 13 thousand years ago by radio carbon,” explains Paquay. “Initially I thought this type of layer could be associated with an impact event because concentration in the proxies of widespread wildfires are sky high. That plus very high levels of iridium (which is one indicator used to indicate extraterrestrial impact events). So the theory was conceptually appealing, but because of the missing impact site, the idea of one or multiple airburst arose.”
To corroborate the theory, Paquay and his colleagues decided to take a three-pronged approach. The first was to replicate the original researchers data, the second step was to look for other tracers, specifically osmium isotopes, of extraterrestrial matter in those rocks, and the third step was to look for these concentrations in other settings. “Because there are so many aspects to the impact theory, we decided to just focus on geochemical evidence that was associated with it, like the concentration of iridium and other platinum group elements, and the osmium isotopes,” says Paquay. “We also decided to look in very high resolution sediment cores across North America, and yet we could find nothing in our data to support their theory.”
The team includes American, Belgian and Canadian researchers. Analysis of the sediments was done both at UHM and in Belgium, using the same sediments from the same interval and indepedently did the analysis work and got similar results. Both the marine and terrestrial sediment records do not indicate that an impact event was the trigger for the transition into the Younger Dryas cold period. “The marine and terrestrial record both complement each other to support this finding,” concludes Paquay. “That’s what makes the beauty of this study.” (From:http://www.eurekalert.org/pub_releases/2009-12/uoha-aoe120709.php)
Archive for the ‘A Science Miscellany’ Category
Tattoos are great. Science tattoos are better. Here is a sample of science tattoos that I find just wonderful from the Science Tattoo Emporium at the Discover Magazine blog page, check out the rest of them here. Below each photo is an explanation of what the tattoo means to each person. I’ve seen many tattoo collections online, but this is the first time I’ve read the tattooed individuals personal interpretation of their tattoo’s meaning.
A grad student who asked to remain anonymous writes, “The tree seems to be a potent symbol of life in human (at least Western) culture, and what better way to augment this symbol by putting the code for life (DNA) at its base? I got this tattoo to commemorate the beginning of my PhD in immunology.”
An immunologist who requests anonymity writes: Nearly every faculty member I meet seems to become instantly curious about my tattoo (attached). I have had it for almost 2 years now. My wife was simply shocked when I returned home after the first sitting. Yes, it took n=3 sittings of ~6 hours each.
Personally, it represents a collection of ideas, experiences, and memories that I chose to mark myself with. I wanted to make a difference with my scientific training as a viral immunologist, so I left my “ivory tower” postdoc position to do translational research at USAMRIID. I’ve spent countless hours working with Ebola, SARS, and other nasty pathogens trying to find vaccines and therapeutics to fight them with. For me personally, it was like opening Pandora’s box. It is brutal, dangerous, and dirty work. I still work with SARS and avian influenza and have NIH/DoD grants to fund the projects. For better or worse, high containment work is my “talent”.
The theme of my tattoo is based upon Greek mythology (Epimetheus/Pandora). When I finally came to embrace the path I took in science, the myth seemed to correlate with my life. Once I took the step forward and opened that “box”, there was no turning back. All of the “plagues” became my scientific passion. The caduceus represents the one last thing to escape from the “box”. I am dedicated to finding ways to combat these pathogens. While slightly irrational, I also viewed the pain and blood as a penance for the animals that must be used to study disease pathogenesis and the efficacy of vaccines and therapeutics I develop with my collaborators. Perhaps I’m a little out there, but I’m trying to make a difference. I’ve marked part of my path in a permanent way!
Vincent, “a fledgling mathematician,” writes:
This tattoo is of a microscope. 90% of the time when I show it to people they say ‘Oh! a telescope!’ I generally don’t correct them, I just get a little uncomfortable and put my shirt back on. Most of the images are copies of SEMs, the background figures include, a fish parasite, anthrax, a scoop of iced cream that has fallen off the cone, flea eggs, bone marrow, and a virus attacking a sun dried tomato! yum!
Jeremiah Drewel, a geology student at the University of Alaska writes, “This is my personal favorite Deinonychus!”
MLR writes: “The Tree of Life–carbon, glucose, light, DNA, and the golden rectangle. A tattoo by Kevin Riley. On the chest of a PhD student in molecular biology.”
“Here is a pic of my tattoo based on the golden spiral and a nautilus shell. i’ve wanted to get this done since high school and finally got up the courage to take the plunge earlier this year. it is now a constant reminder that mathematics is the language of nature.”–Thom
Ben, a philosopher of science grad student, writes: “Darwin sketched the great tree of life and as a philosopher of science and I endeavor to help to complete his project. ‘Metaphysics must flourish, he who understands baboon would do more for metaphysics than Locke’- I believe that by analyzing the universe underneath the lens of evolution we can come to complete Darwin’s project. Darwin, more so than any other great thinker, has provided humanity with an explanation for its existence.
Repaired heart: “I am a nurse and here is my tattoo.”
Zach writes: “It is a half sleeve up my upper right arm based around an image taken by one of the CERN bubble chambers. It is based on this image. I first saw that image my freshman year of college. It had the sublime, simple beauty that only something made of math and science can have. It stuck with me for 8 more years before I actually decided to get it etched into me. Oddly enough, on Valentine’s Day. I guess it was my Valentine’s to physics and science. Oh, and when people ask who drew it, I always respond ‘God.'”
The ancient South American Nasca civilization may have caused its own demise by clear-cutting huge swaths of forest, a new study has found.The civilization disappeared mysteriously around 1,500 years ago, after apparently prospering during the first half of the first millennium A.D. in the valleys of south coastal Peru. Scientists have previously suggested a massive El Niño event disrupted the climate and caused the Nasca’s demise, but new research suggests that deforestation may have also played an important role. (more…)
I wrote this paper for an English class on the String Theory. We had to read physicists Brian Greene’s book The Elegant Universe, and believe me this was challenging when I hadn’t signed up for a physics class. But I actually enjoyed it, and understood most of it (to an extent).
Here is a website that can explain the String Theory a little better than I can http://superstringtheory.com/
http://www.pbs.org/wgbh/nova/elegant/program.html PBS’s NOVA did a 3 hour miniseries on the String Theory. I haven’t been able to watch it as of yet, once I have the time to do so I will post my thoughts.
Although I am not really interested in learning every piece of information regarding the science behind strings, I am interested in their implications to humanity. Read my paper below, do some research on the theory (I recommend Brian Greene’s book), and then ponder my question at the end of my essay.
As dramatic as it sounds, Greene’s book really did change my life and how I look at the world.
This is wrong in so many ways..
Newsflash: It could be a combination of 19th-century mechanics, 21st-century technology — and a 20th-century horror movie.
A Maryland company under contract to the Pentagon is working on a steam-powered robot that would fuel itself by gobbling up whatever organic material it can find — grass, wood, old furniture, even dead bodies. (more…)
Newsflash: University of Arizona biologist Bruce Walsh has identified a new species of moth in southern Arizona. Normally, this is not a big deal. The region is one of the most biologically rich areas in the country and collectors have been finding hundreds of new species for decades. This one, however, is different.
Walsh is a professor of ecology and evolutionary biology and a member of the UA’s BIO5 Institute. He is best known in the science community as an authority on plant and animal breeding, having written one of the leading textbooks on the subject. (more…)
Pheromones, MHCs, ways that humans attract and choose mates is a topic I find very interesting. This type of genetic and behavioral study is something I plan to research more. One thing I am interested in is the human behavior that happens naturally, without forethought. I think biology counts for much more of our personality and behavior than what is given credit for. This research team from Brazil has come up with some interesting evidence that humans are attracted to mates for reasons we don’t completely understand, some suggest body odor or facial structure. In regards to her team’s findings, Professor Maria da Graça Bicalho says “our research has shown clearly that it is differences that make for successful reproduction, and that the subconscious drive to have healthy children is important when choosing a mate.” Somehow we are attracted to another’s biological differences. (more…)