GeoLog

Geoscientific Methods

GeoTalk: Drilling into the crater which contributed to the demise of dinosaurs

GeoTalk: Drilling into the crater which contributed to the demise of dinosaurs

Six months ago, somewhere in the tropical waters off the coast of Mexico, scientists began drilling into one of the most iconic geological features on Earth: the Chicxulub crater; the 66 million year old remnants of a deadly asteroid impact, thought to have contributed to the demise of dinosaurs and most other forms of life which inhabited the Earth at the time.

Today we speak to Sonia Tikoo, Assistant Professor of Planetary Sciences, Department of Earth and Planetary Sciences, Rutgers University, and one of the researchers part of an international team which is currently trying to decipher the secrets held by the rocks of the Chicxulub crater at a core repository in Bremen.

First, could you introduce yourself and tell our readers a little more about your career path so far?

In general, my work involves using the magnetism recorded within rocks to understand problems in the planetary sciences.  I started doing research in palaeomagnetism during college but I really wanted to work in something involving space so I transitioned into planetary science during graduate school.  During my PhD at MIT, I worked on studying the palaeomagnetism of lunar rocks from the Apollo missions to understand the history of the now-extinct lunar dynamo magnetic field.  It was really cool to explore the different ways that small planetary bodies could also generate long-lived magnetic fields lasting a billion years or more.  I subsequently started studying how shock and impact cratering events affect magnetic records within rocks during my postdoc at UC Berkeley, and that experience eventually led me to the work on Chicxulub that I’m doing right now!

Meet Sonia, pictured with colleague William Zylberman, holding up some samples collected from the IODP cores.

Meet Sonia, pictured with fellow palaeomgnetist William Zylberman, holding up some samples collected from the IODP cores.

For those readers who may not be so familiar with the project, could you give us a whistle-stop tour of aims of the research and why it’s important?

In addition to being the crater linked to the demise of the dinosaurs (cool in and of itself!), Chicxulub is also the best-preserved impact structure on Earth and it is the only crater with an intact and well-defined peak ring (a ring of elevated topography within the crater that forms during the collapse stage of crater modification).  As part of IODP/ICDP Expedition 364, we are planning to address a lot of questions regarding this crater, including: (1) how peak rings (stay tuned for our paper on that which is coming out very soon!), (2) how rocks are damaged or weakened by impact shock, (3) how much hydrothermal circulation occurs after the impact, and how long it lasts, and (4) how life recovered within and above the crater following the impact and Cretaceous-Paleogene extinction?

In terms of my specific job…studying the palaeomagnetism of rocks from the crater can be used as a powerful tool to answer some of the aforementioned questions because the magnetizations within rocks can be modified by high temperatures and pressures, and new magnetic minerals can form via hydrothermal activity.  All of these things happen during large impacts on Earth and on other bodies as well, and we see these effects in the crustal magnetism of planetary surfaces.  The entire Science Party is going to be quite busy working on these problems over the next couple years.  What we learn here is not only going to tell us about Chicxulub but also about peak-ring basins across the solar system, and as a planetary scientist I find that angle to be particularly exciting.

What is your role specific role in the project?

Sonia is pictured drilling into cores from the IODP 364 Expedition, to collect smaller samples for palaeomagnetic experiments.

Sonia is pictured drilling into cores from the IODP 364 Expedition, to collect smaller samples for palaeomagnetic experiments.

I’m serving as a palaeomagnetist on the expedition.  There are two groups of scientists associated with Expedition 364 – the Offshore Science Party (the team that recovered the core at sea) and the Onshore Science Party (the team that conducts sampling and preliminary analyses here in Bremen). There wasn’t a magnetometer on the drilling vessel, so I became a member of the Onshore Science Party.  My job here is to collect samples and develop a first-pass dataset of measurements that characterizes the magnetization of the various rock units in the core, spanning both the post-impact sediments and the underlying impactite rocks. The sediment data will eventually be used for magnetostratigraphy and to develop an age model for the post-impact period, and the impactite data gives us a sneak peek at what we will be working with in much greater detail during our post-expedition research as we try to understand the different types of magnetization present in the crater’s peak ring.

So, the experiments are taking place right as we speak?! Can you tell us more about what it is like working at the core repository?

Yes, they are running right now!  Working on an IODP/ICDP expedition is a totally intense, totally rewarding experience!  The Onshore Science Party here in Bremen involves around 45 members of the Onshore Science Party and a team of IODP scientists and technicians working together continuously for a month.

First, one team splits the large drill core into halves.  The core halves then get passed onto teams that do detailed visual descriptions of the cores and some physical properties measurements.

Then the core goes to the sampling room, where we collect specimens for both the immediate measurements we are conducting here in Bremen as well as for the post-expedition research that the Science Party members will be conducting at their home institutions.

Starting bright and early at 7:30 every morning, I drill and prepare sample plugs for moisture and density, P-wave, and paleomagnetic analyses. In the afternoons, I usually shift over to processing magnetic data and writing reports while another paleomagnetist, William Zylberman, conducts measurements in the lab.

The final IODP report writing team. (Credit: Sonia Tikoo)

The final IODP report writing team. (Credit: Sonia Tikoo)

Of course, every other team like physical properties, petrology, biostratigraphy, or geochemistry is doing the same kind of fast-paced work in their own way and we’re always comparing notes and taking advantage of our built-in collaborations. Some scientists have been working on Chicxulub or the K-Pg boundary for decades and others of us (like me!) are first-timers.

There is a fantastic energy associated with having so many talented scientists with all these different avenues of expertise working closely together (and trying to get everything done before our month here is over)!

 

If you want to learn more about the IODP Expedition and associated research, you’ll find some resources here:

 

Geotalk is a regular feature highlighting early career researchers and their work.

Geosciences column: Making aurora photos taken by ISS astronauts useful for research

Geosciences column: Making aurora photos taken by ISS astronauts useful for research

It’s a clear night, much like any other, except that billions of kilometers away the Sun has gone into overdrive and (hours earlier) hurled a mass of charged particles, including protons, electrons and atoms towards the Earth.  As the electrons slam into the upper reaches of the atmosphere, the night sky explodes into a spectacular display of dancing lights: aurora.

Aurora remain shrouded in mystery, even to the scientists who’ve dedicate their lives to studying them. Photographs provide an invaluable source of data which can help understand the science behind them. But, for aurora images to be of scientific value researchers need to know when they were taken and, more importantly, where.

You’ve got to be in the right place at the right time to catch a glimpse of the elusive phenomenon. In the Northern Hemisphere, aurora season peaks in autumn through to winter. Geographically, the best chance of seeing them is at latitudes between 65 and 72 degrees – think the Nordic countries.

That is unless you are an astronaut on the International Space Station (ISS), in which case, you’ve got the best seat in the house!

The orbit of the ISS means it skims past the point at which aurora intensity is at its peak, which also happens to be the point at which they look their most spectacular. Its orbital speed means it can get an almost global-scale snapshot of an aurora, passing over the dancing lights in just under 5 minutes.

Not as much is known about Aurora Australis (those which occur in the southern hemisphere) as we do about the Northern Lights (visible in the northern hemisphere), because there are far less ground-based auroral imagers south of the equator. The ISS orbit means that astronauts photograph Aurora Australis almost as frequently as Aurora Borealis, helping to fill the gap.

Testament to the privileged viewpoint is the hoard of photographs ISS astronauts have amassed over time – perfect for scientists who study aurora to use in their research.

Time-lapse shot from the International Space Station, showing both the Aurora Borealis and Aurora Australis phenomena. Credit: NASA

Except that, until recently, the ISS photographs were of little scientific value because they aren’t georeferenced. The images are captured by astronauts in their spare time using commercial digital single lenses reflector cameras (DSLRs), which can’t pinpoint the location at which the photographs were taken – they were never intended to be used in research.

Now, researchers at the European Space Agency (ESA) have developed a method which overcomes the problem. By mapping the stars captured in each of the photographs and the timestamp on the image (as determined by the camera used to take the photograph), the team are now able to geolocated the images, giving them accurate orientation, scale and timestamp information.

Despite the success, it’s not a straightforward thing to do. One of the main problems is that the timestamps aren’t always accurate. Internal clocks in DSLRs have a tendency to drift. Over the period of a week they can be out by as much as a minute, making it difficult to establish the location of the ISS when the image was captured. This has implications when creating the star map, as the location of the station is used as a starting point.

To resolve the issue, aurora images which also include city lights can be aligned to geographical maps using reference city markers to get a timestamps accurate to within one second or less. In the absence of city lights, images which also capture the Earth’s horizon are aligned with its expected position instead. The correction works best if both city lights and the horizon can be used.

Errors are also introduced when the star maps can’t be fully resolved (due to the original image being noisy, for example) and because the method assumes that auroras originate from a single height, which isn’t true either.

detailed comparison between the ISS image plotted in Fig. 11 (b) and the contemporaneous image acquired by the SNKQ THEMIS ASI (a) . The original ISS image is plotted in (c) . Red and blue symbols trace the locations of the j shaped arc and northern edge of the main auroral arc, respectively, derived from their locations in the THEMIS image. The features are marked with the same coloured arrows in (c) . The magenta arrows point out a vertical feature projected very differently in (a) and (b) .

A detailed comparison between an ISS image of aurora (a) plotted and (b) the contemporaneous image acquired by the SNK THEMIS ASI [ground-based]. The original ISS image (a) is plotted in (c). For more detail see Riechert, et al., 2016.

Comparing images of an aurora on 4 February 2012, captured both by the ISS crew and a ground-based instrument, has allowed the researchers to test the accuracy of their method. Overall, the results show good agreement, but highlight that the projection of the ISS images has to be taken into account when interpreting the results.

Now, a trove of thousands of Aurora Borealis and Australis photographs can be used by researchers to decipher the secrets of one the planet Earth’s most awe-inspiring phenomenon.

By Laura Roberts Artal, EGU Communications Officer

 

References:

Riechert, M., Walsh, A. P., Gerst, A., and Taylor, M. G. G. T.: Automatic georeferencing of astronaut auroral photography, Geosci. Instrum. Method. Data Syst., 5, 289-304, doi:10.5194/gi-5-289-2016, 2016.

Automatic georeferencing of astronaut auroral photography: http://www.cosmos.esa.int/web/arrrgh

The research was accomplished using only free and open-source software. All the images processed to date are made freely available at htttp://cosmos.esa.int/arrgh, as is the software needed to produce them.

Celebrating Earth Science Week!

Celebrating Earth Science Week!

For those not so familiar with the Earth sciences, geosciences and all its subdisciplines might be shrouded in mystery:  boring, unfathomable, out of reach and with little relevance to everyday life. Nothing could be further from the truth!

Earth Science Week, an international annual celebration founded by the American Geosciences Institute in 1998, aims to change the public’s perception of the geosciences.  Since 2011, the London Geological Society also hosts a range of events and activities to raise awareness and better understanding of the Earth sciences.

In 2016, Earth Science Week takes place between 8 and16 October. For the first time, the EGU will run events to mark the special date, all of which we invite you to take part in!

Earth Science Week Photo Competition

From Wednesday 5th to Friday 14th October submit an original photo on any broad theme related to the Earth, planetary and space sciences to our open access image repository, Imaggeo.

For your image to be included in the competition be sure to include the tag #EarthSciWeek when prompted during the upload.

Upon the submission period closing, all entered images will be published to the EGU’s Facebook page. The photograph with most likes, as chosen by the public, will be crowned the competition winner.

The winner will get one free book of their choice from the EGU library and a pack of EGU goodies! We’ll also feature the top five most popular entries on our Instagram.

I’m a geoscientist – Ask me Anything: Live Twitter Q&As

Have you always wanted to know how glaciers move and carve out unbelievable landscapes? How about which emissions cause the most pollution? What are the benefits of publishing in an open access journal vs. a pay-walled publication? If politicians make all the decisions, how can we get them to take scientists more seriously?

If you’ve ever asked yourself these questions, stay tuned or, better still, take part in our daily Earth Science Week live #EGUchat with an EGU member on Twitter. Starting on Monday, every lunchtime, you’ll have the opportunity to put your questions to a range of scientists and EGU experts and discuss a variety of subjects.

Our very own Sarah Connors (@connors SL), the EGU’s Policy Fellow, will kick off a week, of what we hope will be fruitful discussions, by taking questions on all things science policy. Come Tuesday Emma Smith (@emma_c_smith) and Nanna Karlsson (@icymatters), Cryosphere Division Blog editors, will team up to shed light on the processes which operate in the iciest places on the planet.

Wednesday brings editor of the EGU’s open access journal Earth Surface Dynamics (ESurf) and Professor of Physical Geography at the University of Hull, Tom Coulthard (@Tom_Coulthard), who will shed light on the processes which shape our planet and the trials and tribulations of getting published.

If you are interested in natural hazards, how we mitigate, manage them and how they impact on our daily lives, then tune in to the chat on Thursday, where Giorgio Boni (@EguNHpresident), President of the Natural Hazards Division will be answering all your questions!

For the final chat of the week, we bring you Michelle Cain (@civiltalker), an atmospheric scientist and former Atmospheric Division Early Career Scientist Representative. Michelle will be taking questions on gaseous emissions and topics related to the Earth’s atmosphere.

Joining the conversation couldn’t be easier! To put your questions to our experts follow the hashtag #EGUchat on Twitter. Not on twitter or aren’t available during the chats? Not to worry, send us your questions in the comments below or via Twitter, Facebook or Instagram: we’ll ask the experts on your behalf.earth_sci_week_ama_twitter-01

 

Geosciences Column: A new rock outcrop map and area estimation for the entire Antarctic continent

Geosciences Column: A new rock outcrop map and area estimation for the entire Antarctic continent

Antarctica has been known as “the frozen continent” for almost as long as we have known of its existence. It may be the only place on Earth where, instead of information on the extent of glaciers or ice caps, there exists a dataset of all non-icy areas compiled from satellite imagery.

However, this repository is far from perfect: while satellite resolution and coverage have been steadily improving, Antarctica is challenging ground for remote sensing. Ice and cloud cover can be difficult to tell apart, and the low position of the sun in the sky means that long shadows can make snow, ice and rock very difficult to distinguish. As a result, the estimates of the ice-free proportion of the Antarctic continent have been vague, ranging from “less than 1%” to 0.4%.

In a new paper published in the journal The Cryosphere, scientists from British Antarctic Survey and the University of Birmingham show that the continent is even icier than previously thought. Using imagery from NASA’s Landsat 8 satellite, they find that just 0.18% of the continent are ice-free – less than half of previous estimates. This equates to an area roughly the size of Wales on a continent half again as big as Canada.

Lead author Alex Burton-Johnson and his colleagues have developed a new method of accurately distinguishing between ice, rock, clouds and liquid water on Antarctic satellite imagery. Because of the challenging nature of classifying Antarctic satellite imagery, the researchers used only the highest-quality images: they were mostly taken in midsummer, when the sun describes the highest arc in the sky and shadows are smallest, and on days with low cloud cover.

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(Left) The blue squares represent the coverage of the 249 satellite images the researchers used, showing that most rocky areas in Antarctica are clustered along the coastline. The images overlap in many places, allowing for more accurate classification where some clouds occur in pictures. (Right) The new dataset for rock outcrops covers all areas marked in red. The NASA Landsat 8 satellite does not cover areas south of 82°40′ South. Islands such as South Georgia and the South Orkney Islands are too consistently cloudy during the summer period, so the new method cannot be applied here. From : Burton-Johnson et al. (2016).

The huge thickness of the Antarctic ice sheet – more than 4,000m in some places – made the scientists’ job easier: they could exclude large parts of the continent where not even the tallest peaks come close to the ice surface. A total of 249 suitably high-quality images covered those parts of the Antarctic continent that have rock outcrops.

A few locations, however, are too extreme for the new image classification method. Some of the South Orkney Islands and the subantarctic island of South Georgia are covered in heavy cloud for so much of the time even in summer that the researchers could not apply their new method. Here, they had to rely on the older dataset. They also had to exclude parts of the rugged but remote Transantarctic Mountains from the study as the Landsat 8 satellite only covers areas north of 82°40’S.

The code for the new classification methodology is available on GitHub, so that enthusiastic remote sensers can try their hand at further improving it or simply admire the frozen beauty of Antarctica from above.

By Jonathan Fuhrmann

References

Burton-Johnson, A., Black, M., Fretwell, P. T., and Kaluza-Gilbert, J.: An automated methodology for differentiating rock from snow, clouds and sea in Antarctica from Landsat 8 imagery: a new rock outcrop map and area estimation for the entire Antarctic continent, The Cryosphere, 10, 1665-1677, doi:10.5194/tc-10-1665-2016, 2016.

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