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  • kdavis32 9:15 pm on November 19, 2015 Permalink | Reply  

    Why Balloons, and Why Antarctica? 

    The two questions that I get asked about most frequently when describing the STO-2 mission are “why are you putting a telescope on a balloon?” and “why do they need to launch from Antarctica?” These are great questions, but to answer them I need to give you a brief overview of some terminology. You can get a lot of information about the STO-2 mission in my previous blog post here.

    STO balloon fully inflated annotated.jpg

    This is a picture of the STO-1 mission as it was being launched from Antarctica in 2011. The payload looks small in this image, but it is really 21 ft tall! The balloon is as long across as a football field once it is fully inflated.

    The terminology I’ll be talking about is the payload. The payload is the main piece of equipment that is hanging from the balloon, so pretty much everything that launches except the balloon and the parachute. The payload part of the balloon is shown above. The payload has three primary components: the telescope (primary and secondary mirrors sitting within the tube), the instrument (which is the 3 cameras sitting inside the helium tank [dewar], and associated support electronics), and the gondola structure and support packages (the frame of the telescope, the solar panels, navigation cameras, the guidance/communication system, and more).

    STO-2 Hang Test annotated payload

    This diagram shown the different parts of the instrument payload. The telescope is labeled in red, the instrument is labeled in green, and the gondola and major support systems are labeled in white.


    Why Balloons?

    The reason for putting a telescope is the same as why we put them on satellites; you are looking through less air while in space, so the image quality is better.  The atmosphere blocks some of frequencies of light from making it to the ground, so you can’t see that light from the ground. You are probably familiar with this in terms of the Ozone layer of the atmosphere shielding us from the sun’s UV rays, and the terahertz frequencies we observe for the STO-2 mission similarly blocked. Specifically, terahertz light is blocked by water vapor. The altitude our balloon can reach (125,000 ft = 24 miles) is above 99% of the atmospheric water vapor, so we can see the terahertz light shielded from the ground. Even on the driest places on the Earth’s surface, there is too much water vapor in the air to take images over a large region of the sky.

    Another advantage of balloon missions is that they are recoverable payloads. When a satellite has reached the end of its mission, it is either burned up in the atmosphere or sent adrift into deep space. At the end of a balloon mission, the payload is separated from the balloon and returns to Earth on a parachute. A team goes to recover the payload, it gets sent back to the US to make upgrades and fix minor damage that occurs during the landing, and the mission can fly again. The 2 in the STO-2 mission name means that the STO-2 instrument has already flown once before and is on its second flight. The telescope can have different instruments attached to it, and this telescope and gondola structure are on their 6th flight! Previously, the telescope was used for cosmic ray and comet-observing missions. The STO-2 instrument was upgraded and expanded from the STO-1 flight, which flew in 2011. The ability to make quick upgrades and reusing flight-proven hardware is a significant advantage over satellite missions.

    STO1 cut-down

    A picture of the STO-1 payload during the recovery mission. Even though it tipped on it’s side, we were able to re-use almost all of the equipment for the STO-2 flight.

    The final advantage that balloon missions have over satellites is their cost. A satellite mission costs anywhere from a hundred-million dollars to over one BILLION dollars. Balloon missions cost between 1-10 million, depending on the complexity of the payload, mission length, etc. For emerging technology, like terahertz cameras, it makes sense to build and use small-scale balloon payloads to do really cutting-edge science before spending the money to dive into the finer scientific details with large-scale satellites. Balloon missions serve as a great pathway to developing robust technology that can survive the harsh space environment and still achieve the primary science objectives.

    Why Antarctica?

    Now that I have converted you to balloon-spacecraft enthusiasts, I can address the question of why we fly them out of Antarctica rather than out of ASU’s backyard. Believe it or not, the answer has a lot to do with the weather! Space-weather, that is.

    The maximum height the balloon reaches is ~125,000 ft, which is within the stratosphere. The atmospheric pressure at that height is less than 1% of what it is at sea level, but there is still enough air up there to have wind. Near the solstices, June 21 and December 21 each year, the winds at that altitude circle both the Arctic and Antarctic poles. In order for a balloon payload to be recoverable, as discussed above, we want to launch the balloon somewhere with stable weather conditions where we can reliably predict its flight path and plan on where it will land.  Since these polar winds are seasonal, we know approximately when they will occur each year, and can plan accordingly.

    STO1 flight path

    Approximate flight path of the STO-1 mission. The south pole is not in the exact middle of Antarctica, and you can tell where it is from this picture because it is almost exactly in the middle of the red circle! This picture is also pretty cool because you can see how much of the continent is made of permanent ice shelves.

    We also use the circularity of the winds to our advantage.  Since the winds circle the pole, we can launch the payload from a clear site, and wait for the balloon to make one or more rotations and land it near the launch site. You may not think this is important, but when you launch balloons at the poles, there aren’t roads to get to just any point on the continent to go pick up your payload. The outdoors are harsh even in the summer, and the nearest fully-functional hospital is over 1000 miles away. The closer you can land your payload to the station, the easier and safer it is for the recovery team. You can see the flight path of the STO-1 mission in the picture above.

    We launch balloons from Antarctica, but not many get launched from the Arctic. Why? If you look at the picture of Antarctica, what is missing? There aren’t any big towns on Antarctica, in fact, no person lives here permanently. NASA is concerned about the possibility of the balloons landing somewhere unsafe, since once the payload separates from the balloon there is no way to maneuver it for a controlled descent. The northern latitudes are more populous than the southern latitudes, so the risk of the payload causing damage is less in Antarctica. In the Arctic, the flight path of the balloons goes over many countries, some of which have restrictions on what spacecraft they allow to fly over them. Overall, it is safer to launch from Antarctica only.

    Finally, we only launch from Antarctica during the Antarctic summer (which is winter in the northern hemisphere). The main reason for this is because at 77 degrees south, the sun never sets at McMurdo in the summer. This is good for the telescope since it has 24 hour access to sunlight to get collected by the solar panels to power the various systems on the payload. It also makes the payload recovery easier, as well as easier for the scientists and engineers to set everything up.


  • kdavis32 8:10 pm on November 15, 2015 Permalink | Reply  

    Welcome to Antarctica 

    After 4 days of travel, I finally arrived in Antarctica on Friday afternoon. Antarctica is 21 hours ahead of Arizona time (it is on New Zealand time) so it was Thursday evening back in the states.


    Sea-ice as seen from the plane down from Christchurch


    View of the continent from Ross Island. The Ross Ice Shelf is in the foreground.


    Me at LDB with Mt Erebus in the background.

    We left from Phoenix at 6 PM on Monday afternoon. We had a fairly long layover in LAX, and then had a 15 hour flight to Sydney. We had a pretty quick turnaround in Sydney and then flew to Christchurch, NZ. T All said and done, we spent 29 hours in planes or airports, and it because of the 12 hour dateline crossing, we didn’t land until Wednesday afternoon.

    The following morning, we checked into the Clothing Distribution Center for orientation. We all got a final flu shot since they are very concerned with people getting sick out “on the ice”. We also had a computer screening and several safety briefs. After those were done, we went to get our Extreme Cold Weather (ECW) gear issued to us. We tried everything on and packed our bags into bright orange duffels. The ECW gear is a parka nicknamed ‘Big Red’, a pair of snowpants, waterproof boots called ‘bunny boots’, a lighter jacket, a hat and balaclava, goggles, liner gloves and outer gloves, and a fleece pullover and pants. Depending on what your job is, you might not need ALL of that gear, but Bog Red is a must for the cold!

    Friday morning we had to check into the CDC at 5:30 AM, so we caught our shuttle at 4:45 AM. We had another round of safety briefs, and had all of our luggage and ourselves weighed (fun). Then we took a shuttle out to the Spirit of the Medal of Honor, the C-17 taking us down to Antarctica. The C-17 is the second largest US Air Force plane, and is mostly used for cargo. There are only small portals to look out of the plane. The seats are fold-down seats mounted to the sides of the aircraft and face the other side of the plane, not forward. It turns out that the C-17 is such a large aircraft that the ride was actually very smooth. I did get to go up to the cockpit of the plane and take some pictures out of the front windows.


    Arriving in Antarctica. Everybody must wear their outer layers of ECW gear during the plane ride and landing. You can see the white ‘bunny boots’. Most of the plane holds cargo, and there were only ~15 people on our flight, which is small for this time of year.

    The flight takes 5 hours to reach Antarctica. McMurdo station is not actually located on the continent, but is on Ross Island which is the furthest point south accessible by sea. Ross Island is surrounded by a permanent ice shelf (Ross Ice Shelf), which is where the Long Duration Balloon (LDB) hangars are.The plane lands on the ice shelf on regular tires, not on skis. McMurdo has ~1000 people in the summer and ~200 people in the winter. It is the largest of any base in Antarctica. It is 77 degrees south, almost directly underneath New Zealand (2500 miles to the north). It is still another 900 miles down to the South Pole. There is a smaller American base at the Pole, and one on the Antarctic Peninsula underneath Chile/Argentina. The average summer temperature is between 0-25 F, but the wind chill often makes it feel much colder. The South Pole is approximately 10,000 ft in elevation, and so there are gravitationally-driven winds coming off the continent making it very windy most of the time. It will still snow in the summer, although it is much colder, stormier, and snowier in the winter.


    McMurdo station as seen from the tip of Observation Hill. You can see that a lot of the snow melts in the summer. Ross Island is volcanic, ansd so the rocks and dirt are all very dark and absorb heat easily. By the end of January, a lot of the sea ice will melt as well.


    Boarding the Kress transport vehicle after we landed. We take the Kress to the LDB balloon hangar every day as well.


    Glacier on the continent of Antarctica. It was beautifully lit from a part in the clouds.


    Helicopter about to land at McMurdo.

    After we had settled into our rooms, Chris and I took a hike up Observation Hill, which was used by Scott and his crew began their voyage in 1911. There is a cross at the top as a monument to those who perished returning from the south pole during the expedition.


    Panoramic view from on top of Observation Hill.

    The ballooning facility is located ~10 miles from the McMurdo base on the Ross Ice Shelf. It is called LDB for Long Duration Ballooning facility. There are two hangars, each with a different balloon project. There are several other supporting buildings and offices at the camp. The launch pad is behind the hangars and stretches in a circular pattern with a diameter of 2000 ft along the ice shelf. The ice is about 30 yards thick here and is permanent year round, unlike sea ice which is much thinner and recedes throughout the summer. The exact location of the LDB changes slightly each ear as the ice shifts. The buses must traverse a crevasse field on their way to and from base.


    Welcome flags at LDB field location.


    The LDB balloon station. STO-2 is in the right hangar this year. The launch area is behind everything.


    Mt. Erebus as seen from LDB. It is an active volcano, and sometimes you can see ash coming out of the top. While it looks close, it takes nearly a day to reach the base by snowmobile.


    Weddell seal basking in the midnight sun. There is 24 hours of daylight at this time of year in McMurdo. This picture was taken at ~8 PM.

    I am still getting settled into life on the base and preparing for launch. I will post again soon about the progress of the pre-flight assembly.

  • kdavis32 2:39 pm on October 29, 2015 Permalink | Reply  

    STO-2 Mission Overview and Hang Test August 2015 

    I am a graduate student at ASU working on the Stratospheric Terahertz Observatory reflight mission, STO-2. STO-2 is a telescope that hangs underneath a very large helium balloon. The balloon inflates to ~100 meters across and is full of helium gas. The balloon reaches a height of approximately 36 kilometers, which is within the Earth’s stratosphere. The telescope that sits underneath is 0.8 meters in diameter. The STO-2 science objectives are to look at Cold Dark Clouds in the interstellar medium of the Milky Way galaxy. These clouds are thought to further condense into Giant Molecular Clouds, where star formation takes place. Giant Molecular Cloud studies have been ongoing for several decades, but this mission will be one of very few to directly observe the Cold Dark Clouds, and will help us understand how Giant Molecular Clouds form. We will also study how interstellar clouds get disrupted by nearby high mass stars as they give off intense solar wind, and later from supernovas as they die.

    ISM carbon lifecycle

    A diagram showing the lifecycle of gas and dust in the Milky Way. The diagram shows which dominate species of observable chemical transitions are used to study each phase. The STO-2 mission observes CII and NII and OII emission.

    The STO-2 telescope looks at these cloud regions and uses three separate terahertz detectors to record data from these clouds. Each detector is specifically designed to look at photons emitted by different chemical transitions within the Cold Dark Clouds. Together, these three emission profiles help determine important properties of these galactic clouds, including: distinguishing which cloud type we are observing, what the temperature of the cloud is, where the cloud is located within the galaxy (3 dimensionally), how thick the cloud is, how the cloud is moving internally (rotating, expanding, etc), and the what the radiation environment surrounding the cloud is like. This information will lead us to understanding the higher level questions of: what is the complete lifecycle of interstellar gas, study the creation and disruption of star-forming galactic clouds, determine the parameters that effect star formation rate in the galaxy, and provide templates for star formation and stellar/interstellar feedback in external galaxies.

    STO galactic survey region

    The survey region of the STO-2 payload. We will look at a significant fraction of the galaxy which includes looking through the spiral arm and inter-arm regions.

    The STO-2 mission is scheduled for launch from McMurdo Station in Antarctica in December of 2015. Recently, I traveled to Palestine, TX to help with the integration and testing of the STO-2 payload. This test is critical to to ensure that the instrument is balanced and all of the equipment fits into its specified location, make sure that the data collected by the instrument is properly stored by the onboard computers and relayed by satellite to mission control, and to test that that the telescope is properly aligned and can receive satellite pointing commands.

    There are two major ‘teams’ working on the full STO-2 payload. The first is the instrument team, who are in charge of making sure all the receivers are working properly. The receivers we use are Hot Electron Bolometers (HEBs) for our CII and NII emission. These detectors need a lot of support electronics to make them work properly, and so the instrument team is in charge of focusing the light from the secondary mirror onto the detectors, through a series of lenses, mirrors, and windows. We also shine a second, high powered light source created by us onto the HEB detectors, which acts as a light ‘pump’ for our detectors. We call the light pump a Local Oscillator (LO). The HEBs convert the photons from the LOs and the gas clouds into lower frequency electrical signals. The electrical signals get amplified and converted into digital signals, which are read by our spectrometers. A lot of the electrical equipment, especially the HEBs, need to be supercooled to function properly. The camera sits inside a big dewar, which holds liquid helium at 4 degrees above absolute zero. The instrument team is not only responsible for making sure the electronics are properly aligned, they also need to make sure each piece of equipment is kept at its desired temperature.


    Members of the instrument team working on the electronics outside of the dewar during the Hang Test. The dewar is the white tank in the middle-left of the image with a lot of electronics boxes attached to it. We paint everything flight-worthy white to reflect as much sunlight as possible which helps keep it cool.  

    The other team for the STO-2 mission is the telescope team. While the instrument team sets up the receiver system, the telescope team sets up the majority of the structure of the payload as well as a lot of support systems. The telescope team handles the telescope itself, which is the primary and secondary mirrors, sitting along the long gold baffle. They also set up the guidance system, which uses visible light cameras to triangulate which direction the telescope is pointing, and uses gyroscopes and reaction wheels to keep the telescope steady and slew it back and forth to take an image of the cloud regions we study. The telescope gondola has two sets of solar panels to provide power to the telescope subsystems, and we have batteries on-board to store the extra energy. The telescope team is in charge of thermal control for all the equipment that isn’t cooled by the helium tank in the dewar. Finally, the telescope team provides contact to and from the telescope, which allows us to communicate via satellite with the telescope while in flight to check on its stats, upload pointing commands, and collecting the data through mission control.


    The telescope with the dewar attached but before the solar panels are installed. The guidance system has also not been installed underneath the telescope. The gondola pictured here is just shy of 20 ft. tall.

    The hang test is the first time that the instrument and telescope come together and all the electronics are hooked up to each other. The hang test takes place at the Columbia Science Balloon Facility in Palestine, TX. It is a small NASA center where they used to launch balloon missions, but cannot do so any longer now that Palestine is a booming metropolis (heh). You can still go out and see the gigantic launch pad, which is a 1000 ft diameter concrete circle, surrounded by an even wider open space now used for growing hay.


    The CSBF launch pad during the day (lower) and at night (upper). I wanted to include the sunset picture because it was very pretty. It was not as hot in Texas in August as in Phoenix, but it was about 3 times as humid. You can’t see the launch pad as well from these angles, but it is very large and quite pleasant to take a stroll around.


    During the hang test, the entire gondola payload is actually hung from a crane! The test not only tests the hardware system but also the software system, which is very complex, elegant, and designed by the STO-2 team specifically for this mission. The dewar and the telescope are integrated inside a large hanger. On the day of the test, a crane in the hangar lifts the payload to the door, where it is transferred to a separate crane and taken outside. The hanging payload is free to point and rotate, and it can communicate via satellite. Mission control (Houston) send pointing commands to the gondola, and the team can determine if the telescope is pointing correctly. We also take some ‘fake’ data and make sure it is stored and processed correctly. Since things went well, the hang test only took ~ 3 hours. However, there were two straight weeks of 10-16 hour days necessary to get us to that point (and one 22 hour day!). The success of the hang test shows that the mission is prepared to be sent down to Antarctica for launch. The entire system has to be taken apart to be shipped, so all that hard work gets immediately torn apart.


    The STO-2 instrument and telescope teams in front of the complete instrument gondola. Hang test success!


    The gondola only needs to hang by a few feet to be able to swing properly. You can see the back sides of the solar panels in this view, as well as the instrument support package underneath the dewar. The communication antennas are sticking out on the boom at the very top of the payload.

    Davis Groppi STO2 hanging

    Me and my adviser Chris Groppi with the payload. You can see the extent of the instrument better in this view.

  • gwynethnotpaltrow 10:02 am on August 29, 2015 Permalink | Reply
    Tags: @realscientists   

    I’ll be curating the @realscientists twitter account for one week, starting tonight. I’ll be co-convening a session with Steve Macko on stable isotopes in ecological research at the Long Term Ecological Research Conference. Be sure to follow!

  • Ben 9:29 am on August 16, 2015 Permalink | Reply  

    ECHO in West Virginia 

    Dr. Danny Jacobs and his astounding team of undergraduate students (Ben Stinnett, Jacob Burba, and Lauren Turner) and graduate student Abraham Neben (MIT), have arrived in Green Bank, West Virginia for a week of field work at the National Radio Astronomy Observatory site. The highlight of the Green Bank site is the Green Bank Telescope, at 100m it is the world’s largest fully steerable dish and is used to hunt for pulsars and other exotic objects in deep space. However, this amazing telescope is not why the team is there; it is currently down for maintenance.


    The 300′ Green Bank Telescope

    The GBT being offline is actually a primary contributor to the field work being conducted right now, as this allows the team to generate radio noise with their instruments without disrupting other observations. The instrument in question is ECHO – the External Calibrator for Hydrogen Observatories. ECHO is an instrument developed by Dr. Jacobs in Professor Bowman’s Low frequency Cosmology lab at ASU to serve as a precision calibration source for new cosmology arrays. It uses a calibrated transmitting antenna mounted to an Unmanned Aerial Vehicle to provide a known reference signal for calibrating low-frequency antennas. ECHO team member Jacob Burba, physics major at ASU, explains that the “Calibration of Wide-field arrays has historically proven to be very difficult. Using an Unmanned Aerial Vehicle we’ll finally be able to control all of the variables and approach a new level of precision necessary for the desired cosmological measurements.  Plus: drones!.”

    ECHO multirotor taking flight!

    ECHO multirotor taking flight!

    At the NRAO Green Bank Site, the team is testing their instrument for eventual use on the Hydrogen Epoch of Reionization Array (HERA), which is currently under construction in South Africa. When finished, HERA will have 300 individual 14m dishes packed together to form one of the largest single collecting areas in the world. Understanding this array presents a unique calibration problem which the team hopes to solve with their UAVs.


    Spending their morning in the field to take advantage of the good weather, the team was able to make four successful flights over the HERA testbed, the data from which is currently being processed. Should the excellent flying weather continue, you can expect more flights throughout the week!

    The ECHO team hard at work!

    The ECHO team hard at work!

  • gwynethnotpaltrow 12:14 pm on July 20, 2015 Permalink | Reply
    Tags: ,   

    Congratulations, Jake! 

    Congratulations to Jake Smith on his successful Master’s defense entitled “Raccoon Scavenging and the Taphonomic Effects on Early Human Decomposition and PMI Estimation.”

    Jake Smith's successful Master's defense

    Jake Smith’s successful Master’s defense

    Jake did a careful study of how raccoons can scavenge human bodies, leading to important insights in the patterns of how and when they scavenge. Megyesi et al (2005) published a study in the Journal of Forensic Sciences to estimate PMI (postmortem interval, or time since depth), based on rating changes in a corpse’s color, insect activity and soft tissue changes. However, Megyesi’s study did not include the effect of scavenging by animals. By using donors to ARF with known dates of death, Jake has been able to show that scavenging can cause estimates of PMI to be off significantly – which could have important implications for forensic cases. In addition, because raccoons are common scavengers throughout much of the US, this is an important consideration a wide geographic region.

    In Texas State, the scavengers are not raccoons, but vultures. They also do a lot of research on vultures, who play a critical role in many ecosystems. The patterns of scavenging for these two animals are quite different.

    There are now six facilities in the US for studying the processes of human decomposition, and it’s clear that these are really all needed. Differences in scavengers, terrain and climate can cause dramatic differences in how people decompose, and it’s important to understand how those differences may be reflected in discovered remains.

    Another thing I learned in Tennessee is how many forensic cases never make the news. For every case that makes the national news, there are many that never do. Some of these are skeletal remains for people that may have died of natural causes, or suicides. However, without highly trained forensic anthropologists, those manner of death determinations can be difficult. Although this type of research may be macabre or disturbing to many people, it is critical in solving cases and bringing criminals to justice.

  • gwynethnotpaltrow 7:30 pm on July 16, 2015 Permalink | Reply
    Tags: , , , Jake Smith, taphonomy   

    Team effort 

    Doing this research involves a significant amount of physical labor as well as intellectual effort. I’m extremely grateful for all the help I’ve had both at UT and Texas State. Over the last week, we’ve placed five donors for this project, three in surface plots protected by cages to prevent scavenging and two in burials. This definitely wouldn’t be possible without the incredible assistance of undergrads (many volunteers!), interns, grad students and faculty keeping this complex facility running smoothly. From digging graves, placing donors, taking daily photographs and carefully documenting the processes of decomposition, there’s a lot of good will despite all the hard work and olfactory issues associated with decomposing bodies.

    From left to right, Sydney Shaver, Jessica Newcomb, Victoria Bates, Christine Bailey (volunteer coordinator), Abigail Brennan and Tiffany Saul (grad student). Bonnie Simmons not pictured. We worked hard to get our placements done before severe thunderstorms swept back in.

    From left to right, Sydney Shaver, Jessica Newcomb, Victoria Bates, Christine Bailey (volunteer coordinator), Abigail Brennan and Tiffany Saul (grad student). Bonnie Simmons not pictured. We worked hard to get our placements done before severe thunderstorms swept back in.

    Two other grad students, Angela Dautartas and Jake Smith, also put in far more hours than they are paid for. They do tasks ranging from picking up donors, completing donor intake, building cages to keep out scavengers (mostly raccoons) as well as doing their graduate research. Jake has 15 years experience in managing a funeral home, so he does much of the coordination with donors and their families. He works very hard to make sure the donation process is going to work emotionally for the donors’ families, while balancing the needs of researchers. Although he’s only wearing one hat in the image below, he wears many in real life.

    University of Tennessee, Knoxville grad students Angela Dautartas and Jake Smith (wearing hat) take proper precautions when handling human remains.

    University of Tennessee, Knoxville grad students Angela Dautartas and Jake Smith (wearing hat) take proper precautions when handling human remains.

    Many of the donors have pre-willed their bodies to the facility, filling out extensive paperwork about where they were born, where they’ve lived and detailed medical histories. This information is critical not just for current research, but because later on the donors will become part of the largest modern skeletal collection in the world, with more than 1200 individuals. If you look at the literature of forensic anthropology, you’ll quickly realize that many of studies estimating age, sex and racial group come from this collection.

    Angela and Jake showed me the steps behind the intake process. This is where donors are carefully photographed, with any injuries, trauma and the condition of teeth are carefully noted. The donors are weighed and measured, and samples of blood, hair and nails are taken for future analysis. Jake is familiar with the many research studies going on at one time, and will evaluate which studies any particular individual donor will be involved in. They are then taken up to the facility, where they will be photographed and observed daily throughout decomposition.

  • gwynethnotpaltrow 10:14 am on July 15, 2015 Permalink | Reply
    Tags: , ,   

    water, water everywhere! 

    During the time between my two sites, I worked on getting as much data as I can to make sure everything is working properly. With the assistance of Vince Debes, I measured the elemental composition of the water samples I collected at Texas State, and was able to compare them to the values I estimated from, a fantastic free resource from the University of Utah by Professor Gabriel Bowen (among others). If you’re interested in how they’re able to predict what isotope values should occur at any particular site, they have a great tutorial here.

    The precipitation samples I measured – two rainwater samples and one throughfall sample – at sites at Texas State are the same within analytical error, and very similar to the values predicted by Isomap. Throughfall is rainwater that falls through vegetation like trees, and collects dirt, dust and material from the vegetation – and you can see the difference from rainfall in the picture below.

    rainwater vs throughfall

    The middle sample was from a site in the middle of a set of trees and is throughfall. The rainfall samples on the right and left were located in open areas.

    Stable isotopes are always measured relative to a standard, because we can measure small differences between things far more accurately than the absolute value of something. If you were looking at a group of people, it’s far easier to tell that Jeanette is about 1 inch taller than Maria, than to tell that Jeanette is five foot four inches tall. In the next post, I’ll discuss the results in more detail.

    The autosampler for the Liquid-Water Isotope Analyzer.

    The autosampler for the Liquid-Water Isotope Analyzer.

  • gwynethnotpaltrow 6:38 pm on July 10, 2015 Permalink | Reply
    Tags: , ,   

    Dr. Bass! 

    I’m now in Tennessee at the original “Body Farm” continuing my research. Today, I was thrilled to have the opportunity to meet Dr. Bass, who started the facility (Anthropological Research Facility, or ARF) in 1981 to scientifically study the processes of human decomposition. In the beginning, doing this type of research offended a lot of people, but much of what we know about how to estimate time of death with insect activity, visual and chemical changes comes from him and his students. You can actually take a short video tour with Dr. Bass through the Body Farm here, but please note that there are images of human skeletal remains in the video.

    Dr. Bass started an Anthropological Response Team that would go out to crime scenes with human remains in Tennessee – previously, law enforcement would just bring him a skull and perhaps a couple of bones. His idea that looking at the entire context of the scene by someone who was an anthropological expert made him a real visionary. He’s also a board-certified forensic anthropologist – one of only 106 in all of US history!

    As with many scientists, and perhaps anthropologists in particular, he’s a wonderful storyteller. We chatted for some minutes and he told me of cases he’s worked and I could tell he’s still passionate about helping families to figure out what happened to their loved ones.

    The term “Body Farm” was popularized by Patricia Cornwell’s novel, who has a main character based on Dr. Bass. With John Jefferson, Dr. Bass has written eight novels as well as an autobiography, so clearly he’s been honing his storytelling abilities for many years.

    Meeting Dr. Bass!

    Meeting Dr. Bass!

  • gwynethnotpaltrow 5:44 pm on June 23, 2015 Permalink | Reply
    Tags: , , ,   

    Coming…and going 

    I survived the weather in Texas, and have returned to ASU just long enough to unpack and restock supplies before going to the University of Tennessee, Knoxville. My samples made it back safely, but most measurements will have to wait until after my trip to Tennessee.

    Lab Technician Trevor Martin demonstrates the use of the liquid nitrogen ball mill.

    Lab Technician Trevor Martin demonstrates the use of the liquid nitrogen ball mill.

    Tiffany Saul, a graduate student at UTK, will be coming here to ASU this fall to run some isotope analyses on the samples, as well as some of her thesis samples. She’s just finish going to IsoCamp through the University of Utah, so she’ll have a good opportunity to apply what she’s just learned about stable isotopes in ecology to our studies of the Body Farm in Tennessee. Utah has added a second course, SPATIAL, to cover the rapidly emerging topic of “isoscapes”, or isotopic landscapes.

    Oxygen and hydrogen isoscapes in plants, from Jason West’s group at Texas A&M.

    The concept that isotope ratios vary in systematic and predictable ways with geography is at the heart of the idea of figuring out where people were born or have moved. Our bodies are built when we eat food (carbon, nitrogen, strontium, even lead!), and drink water (oxygen and hydrogen). This leaves everyone with a measurable chemical and isotopic signature of where you live. This concept has been used for several decades in ecology and anthropology, to help understand animal migrations and ancient populations. It’s been championed in forensics and nutrition by a handful of researchers for more than a decade, but it has taken a while to become widespread. It employs concepts from geology (isotopic fractionation and measurements, large scale climate patterns), biology (metabolism), chemistry, and culture (food choices, migrations), so it requires researchers to cross boundaries between traditional scientific disciplines. It’s a very powerful tool that is finding wider application, and I’m excited to be a part of this emerging discipline.


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