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Solving the dark energy mystery: A new sky survey assignment for a 45-year-old telescope

SMU and other members of a scientific consortium prepare for installation of the Dark Energy Spectroscopic Instrument to survey the night sky from a mile-high mountain peak in Arizona

As part of a large scientific consortium studying dark energy, SMU physicists are on course to help create the largest 3-D map of the universe ever made.

The map will emerge from data gathered by the Dark Energy Spectroscopic Instrument (DESI) being installed on the Nicholas U. Mayall Telescope atop a mountain in Arizona.

The map could help solve the mystery of dark energy, which is driving the accelerating expansion of the universe.

DESI will capture about 10 times more data than a predecessor survey of space using an array of 5,000 swiveling robots. Each robot will be carefully choreographed to point a fiber-optic cable at a preprogrammed sequence of deep-space objects, including millions of galaxies and quasars, which are galaxies that harbor massive, actively feeding black holes.

“DESI will provide the first precise measures of the expansion history of the universe covering approximately the last 10 billion years,” said SMU physicist Robert Kehoe, a professor in the SMU Department of Physics. “This is most of the 13 billion year age of the universe, and it encompasses a critical period in which the universe went from being matter-dominated to dark-energy dominated.”

The universe was expanding, but at a slowing pace, until a few billion years ago, Kehoe said.

“Then the expansion started accelerating,” he said. “The unknown ‘dark energy’ driving that acceleration is now dominating the universe. Seeing this transition clearly will provide a critical test of ideas of what this dark energy is, and how it may tie into theories of gravitation and other fundamental forces.”

The Mayall telescope was originally commissioned 45 years ago to survey the night sky and record observations on glass photographic plates. The telescope is tucked inside a 14-story, 500-ton dome atop a mile-high peak at the National Science Foundation’s Kitt Peak National Observatory – part of the National Optical Astronomy Observatory.

SMU researchers have conducted observing with the Mayall. Decommissioning of that telescope allows for building DESI in it’s place, as well as reusing some parts of the telescope and adding major new sytems. As part of DESI, SMU is involved in development of software for operation of the experiment, as well as for data simulation to aid data anlysis.

“We are also involved in studying the ways in which observational effects impact the cosmology measurements DESI is pursuing,” Kehoe said. SMU graduate students Govinda Dhungana and Ryan Staten also work on DESI. A new addition to the SMU DESI team, post-doctoral researcher Sarah Eftekharzadeh, is working on the SMU software and has studied the same kinds of galaxies
DESI will be measuring.

Now the dome is closing on the previous science chapters of the 4-meter Mayall Telescope so that it can prepare for its new role in creating the 3-D map.

The temporary closure sets in motion the largest overhaul in the telescope’s history and sets the stage for the installation of the Dark Energy Spectroscopic Instrument, which will begin a five-year observing run next year.

“This day marks an enormous milestone for us,” said DESI Director Michael Levi of the Department of Energy’s Lawrence Berkeley National Laboratory , which leads the project’s international collaboration. “Now we remove the old equipment and start the yearlong process of putting the new stuff on.”

More than 465 researchers from about 71 institutions are participating in the DESI collaboration.

The entire top end of the telescope, which weighs as much as a school bus and houses the telescope’s secondary mirror and a large digital camera, will be removed and replaced with DESI instruments. A large crane will lift the telescope’s top end through the observing slit in its dome.

Besides providing new insights about the universe’s expansion and large-scale structure, DESI will also help to set limits on theories related to gravity and the formative stages of the universe, and could even provide new mass measurements for a variety of elusive yet abundant subatomic particles called neutrinos.

“One of the primary ways that we learn about the unseen universe is by its subtle effects on the clustering of galaxies,” said DESI collaboration co-spokesperson Daniel Eisenstein of Harvard University. “The new maps from DESI will provide an exquisite new level of sensitivity in our study of cosmology.”

Mayall’s sturdy construction is perfect platform for new 9-ton instrument
The Mayall Telescope has played an important role in many astronomical discoveries, including measurements supporting the discovery of dark energy and establishing the role of dark matter in the universe from measurements of galaxy rotation. Its observations have also been used in determining the scale and structure of the universe. Dark matter and dark energy together are believed to make up about 95 percent of all of the universe’s mass and energy.

It was one of the world’s largest optical telescopes at the time it was built, and because of its sturdy construction it is perfectly suited to carry the new 9-ton instrument.

“We started this project by surveying large telescopes to find one that had a suitable mirror and wouldn’t collapse under the weight of such a massive instrument,” said Berkeley Lab’s David Schlegel, a DESI project scientist.

Arjun Dey, the NOAO project scientist for DESI, explained, “The Mayall was precociously engineered like a battleship and designed with a wide field of view.”

The expansion of the telescope’s field-of-view will allow DESI to map out about one-third of the sky.

DESI will transform the speed of science with automated preprogrammed robots
Brenna Flaugher, a DESI project scientist who leads the astrophysics department at Fermi National Accelerator Laboratory, said DESI will transform the speed of science at the Mayall Telescope.

“The telescope was designed to carry a person at the top who aimed and steered it, but with DESI it’s all automated,” she said. “Instead of one at a time we can measure the velocities of 5,000 galaxies at a time – we will measure more than 30 million of them in our five-year survey.”

DESI will use an array of 5,000 swiveling robots, each carefully choreographed to point a fiber-optic cable at a preprogrammed sequence of deep-space objects, including millions of galaxies and quasars, which are galaxies that harbor massive, actively feeding black holes.

The fiber-optic cables will carry the light from these objects to 10 spectrographs, which are tools that will measure the properties of this light and help to pinpoint the objects’ distance and the rate at which they are moving away from us. DESI’s observations will provide a deep look into the early universe, up to about 11 billion years ago.

DESI will capture about 10 times more data than a predecessor survey
The cylindrical, fiber-toting robots, which will be embedded in a rounded metal unit called a focal plate, will reposition to capture a new exposure of the sky roughly every 20 minutes. The focal plane assembly, which is now being assembled at Berkeley Lab, is expected to be completed and delivered to Kitt Peak this year.

DESI will scan one-third of the sky and will capture about 10 times more data than a predecessor survey, the Baryon Oscillation Spectroscopic Survey (BOSS). That project relied on a manually rotated sequence of metal plates – with fibers plugged by hand into pre-drilled holes – to target objects.

All of DESI’s six lenses, each about a meter in diameter, are complete. They will be carefully stacked and aligned in a steel support structure and will ultimately ride with the focal plane atop the telescope.

Each of these lenses took shape from large blocks of glass. They have criss-crossed the globe to receive various treatments, including grinding, polishing, and coatings. It took about 3.5 years to produce each of the lenses, which now reside at University College London in the U.K. and will be shipped to the DESI site this spring.

Precise measurements of millions of galaxies will reveal effects of dark energy
The Mayall Telescope has most recently been enlisted in a DESI-supporting sky survey known as the Mayall z-Band Legacy Survey, which is one of four sky surveys that DESI will use to preselect its targeted sky objects. SMU astrophysicists carried out observing duties on that survey, which wrapped up just days ago on Feb. 11, to support the coming DESI scientific results.

Data from these surveys are analyzed at Berkeley Lab’s National Energy Research Scientific Computing Center, a DOE Office of Science User Facility. Data from these surveys have been released to the public at http://legacysurvey.org.

“We can see about a billion galaxies in the survey images, which is quite a bit of fun to explore,” Schlegel said. “The DESI instrument will precisely measure millions of those galaxies to see the effects of dark energy.”


Levi noted that there is already a lot of computing work underway at the Berkeley computing center to prepare for the stream of data that will pour out of DESI once it starts up.

“This project is all about generating huge quantities of data,” Levi said. “The data will go directly from the telescope to the Berkeley computing center for processing. We will create hundreds of universes in these computers and see which universe best fits our data.”

Installation of DESI’s components is expected to begin soon and to wrap up in April 2019, with first science observations planned in September 2019.

“Installing DESI on the Mayall will put the telescope at the heart of the next decade of discoveries in cosmology,” said Risa Wechsler, DESI collaboration co-spokesperson and associate professor of physics and astrophysics at SLAC National Accelerator Laboratory and Stanford University. “The amazing 3-D map it will measure may solve some of the biggest outstanding questions in cosmology, or surprise us and bring up new ones.” — Berkeley Lab and SMU

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Female students exposed briefly to charismatic career women are inspired to pursue male-dominated field

Easy, inexpensive experiment briefly sent inspiring female role models into intro to econ classes and sharply increased college female interest in the male-dominated, well-paying field of economics.

A low-budget field experiment to tackle the lack of women in the male-dominated field of economics has been surprisingly effective, says the study’s author, an economist at Southern Methodist University, Dallas.

Top female college students were inspired to pursue a major in economics when exposed very briefly to charismatic, successful women in the field, according to SMU economist Danila Serra.

The results suggest that exposing young women to an inspiring female role model succeeds due to the mix of both information and pure inspiration, Serra said.

“The specific women who came and talked to the students were key to the success of the intervention,” she said. “It was a factor of how charismatic and enthusiastic they were about their careers and of how interesting their jobs looked to young women.”

Given the simplicity and low-cost of the intervention, similar experiments could be easily conducted in other male-dominated or female-dominated fields of study to enhance gender diversity.

Serra’s results showed that among female students exposed to the enthusiastic mentors there was a 12-percentage point increase in the percentage of female students enrolling in the upper-level Intermediate Microeconomics course the following year — a 100% increase, or doubling, for that demographic.

Not surprisingly, given that the intervention was targeted to female students, Serra found that the role model visits had no impact on male students.

But astonishingly it had the greatest impact on high-achieving female students.

“If we restrict the analysis to the top female students, the students with a GPA of 3.7 or higher, the impact is remarkable — it is a 26 percentage points increase,” Serra said. “So this intervention was especially impactful on the top female students who perhaps were not thinking about majoring in economics.”

The results were very surprising to Serra, an assistant professor in the SMU Department of Economics in Dedman College who teaches the upper-level class Behavioral and Experimental Economics. Serra’s research relies on laboratory and field experiments, a relatively new methodology in the field of economics. She launched and is co-leader of the Laboratory for Research in Experimental Economics at SMU.

“I didn’t think such limited exposure would have such a large impact,” Serra said. “So this is telling me that one of the reasons we see so few women in certain fields is that these fields have been male-dominated for so long. This implies that it is very difficult for a young woman to come into contact with a woman in the field who has an interesting job in the eyes of young women and is enthusiastic about her major and her work. Young men, on the other hand, have these interactions all the time because there are so many male economics majors out there.”

Co-author on the research is Catherine Porter, associate professor of economics at Heriot-Watt University, Edinburgh, Scotland, and Serra’s former Ph.D. classmate at the University of Oxford.

“The gender imbalance in economics has been in the news a lot lately, and much of the discussion has been very negative,” said Porter. “This study offers something positive: a cheap way of improving the gender balance. The results can hopefully be used by other schools in order to redress the low numbers of women that major in economics – women have a lot to offer and should consider economics as a subject that is interesting and varied for a career.”

Serra reported the findings, “Gender differences in the choice of major: The importance of female role models,” on Jan. 6 in Philadelphia at the 2018 annual meeting of the Allied Social Sciences Association. Hers is one of many findings on gender and gender differences in economics presented at a session organized by the Committee for the Status of Women in the Economics Profession.

Inspiring the individual is the best tool to recruit and retain
Serra launched the study after SMU was one of 20 U.S. universities randomly chosen by Harvard economics professor Claudia Goldin for the Undergraduate Women in Economics Challenge. The project awarded each university a $12,500 grant to develop a program freely chosen by the universities to test the effectiveness of a deliberate intervention strategy to recruit and retain female majors.

Nationally, there’s only about one woman for every three men majoring in economics. SMU has a large number of economics majors for a school of its size, with 160 a year. The gender imbalance, however, is greater at SMU than the national average, with only one woman to every four men.

Serra developed her intervention based on her own experience as a Ph.D. student at the University of Oxford several years ago.

“I started thinking about role models from my personal experience,” Serra said. “As a student, I had met many female professors in the past, but my own experience taught me that inspiration is not about meeting any female professor — it’s about meeting that one person that has a huge charisma and who is highly inspiring and speaks to you specifically.”

Serra said that’s what she experienced as a graduate researcher when she first met Professor Abigail Barr, who later became her Ph.D. advisor.

“I know for a fact that that is why I decided to do a Ph.D. in economics, because I was greatly inspired by this person, her experiences and her research,” she said. “So I thought it would be interesting to see whether the same could work for a general student population.”

Two inspiring women role models, 15 minutes, four classrooms
Serra asked two of her department’s top undergraduate female economics students to take the lead in choosing the role models.

The students, Tracy Nelson and Emily Towler, sorted through rosters of SMU economics alums and shortlisted 18 men and women that they thought were working in interesting fields – which purposely excluded stereotypical jobs in banking and finance – and then carried out scripted interviews with a subset of who agreed to be interviewed via Skype to get additional information about their career path and to assess their charisma.

The students ultimately found two alumnae, Julie Lutz and Courtney Thompson, to be the most inspiring. Lutz, a 2008 graduate, started her career in management consulting but, shortly after, decided to completely change her career path by going to work for an international NGO in Nicaragua, and then as a director of operations at a toy company based in Honduras. Lutz now works in Operations at a fast-growing candy retail company. Courtney Thompson, class of 1991, has had a stellar career in marketing, becoming the senior director of North American Marketing and Information Technology at a large international communications company, with the unique claim of being not only a female econ major at a time when that was exceedingly rare, but also African American in a white dominated field.

Serra invited each woman to speak during the Spring 2016 semester for 10 to 15 minutes to four Principals of Economics classes that she had randomly selected from a set of 10. The Principles classes are very popular, with about 700 students total from a variety of desired majors, and are typically gender balanced. The imbalance, said Serra, starts the following year with Intermediate Microeconomics, which is a requirement for upper-level economics courses and so is a good indicator of a desire to major in economics.

Serra offered each role model an honorarium for speaking, but each woman declined and indicated they were happy to be back on campus sharing with students. Serra told the speakers nothing of the purpose of the research project, but encouraged each one to explain to the class why they majored in economics and to be very engaging. She directed them to approach the students with the following question in mind: “If you had to convince a student to major in economics, what would you say?”

Thompson, Serra said, during her college days played SMU’s costumed Peruna mascot, and today retains a “bubbly, big personality, that makes her extremely engaging.” In her classroom visits, Thompson described her experience working and being extremely successful in marketing with an economics degree, while being surrounded by business majors. Lutz, being still in her 20s, was very easy for the young women in the classrooms to identify with, and her experience working in the non-profit and in developing countries may have been especially appealing to them.

Young women judge best who will inspire them
Serra believes that a key to the success of the intervention was the fact her two female economics students actively participated in the selection of the role models.

“The most important thing about the project was that I realized I needed current female students to choose the role models,” Serra said. “I’m not that young anymore, so I’m probably not the best person to recognize what is inspiring to young women. I think young female students are in the best position to tell us what is most inspiring to them.”

In November the directors and officers of the International Foundation for Research in Experimental Economics honored Serra as the inaugural recipient of the $50,000 Vernon L. Smith Ascending Scholar Prize. The Smith Prize is described by the foundation as a “budding genius” award.

For her highly cited corruption research, Serra uses lab experiments to study bribery, governance and accountability, questioning long-standing assumptions. Some of her findings are that corruption declines as perpetrators take into account social costs of their illegal activities, and as victims share information about specific bribery exchanges through online reporting. Serra’s current research agenda also includes experimental work on gender differences in preferences, behaviors and outcomes. — Margaret Allen, SMU

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Cyber grad and U.S. Marine Corps vet Michael Taylor proved his mettle as an outstanding student researcher

‘Outstanding student in computer science & engineering’ graduates Dec. 16 with master’s degree and Raytheon ticket to a Ph.D.

Michael Taylor will be the first to tell you that he was not ready for college when he graduated from Plano East High School in 2006. And he’ll also tell you that nobody was more surprised than he was when SMU admitted him in 2014, a little later than the average undergrad.

But Taylor’s disciplined approach to life, honed through five years in the Marine Corps, combined with the intelligence he learned to tap, has earned him a master’s degree from SMU’s Lyle School of Engineering that will be awarded Dec. 16. And after proving his mettle as a student researcher in Lyle’s Darwin Deason Institute for Cyber Security, Taylor has been awarded the first Raytheon IIS Cyber Elite Graduate Fellowship, which will fund his Ph.D. in quantum computing at SMU and then put him to work as an employee at Raytheon.

“Michael Taylor stood out to me when I first had him in an undergraduate class,” said Mitch Thornton, research director for the Deason Institute and Cecil H. Green Chair of Engineering at SMU. “I could sense there was something special about him and that he had a lot of talent. I actively encouraged Michael to do research with me and he has excelled in everything I have asked him to work on. He is a credit to the student body of SMU’s Lyle School, and a credit to the nation.”

Taylor learned to focus on the details in the Marine Corps. He had sampled community college very briefly after high school, but it didn’t stick. He knew he didn’t have skills to trade for a decent job, so joining the Marine Corps made sense to him.

“Honestly? In retrospect, I wasn’t ready for school,” Taylor acknowledged.

After the Marines, finally ready for college
Taylor’s dad was an SMU engineering alumnus, and this was not the career path he’d envisioned for his son. But it’s funny how things work themselves out. Taylor completed Marine basic training, and took an aptitude test to determine where his skills might fit the Marine Corp mission. He did very, very well.

“My score on that test – I qualified for every enlisted job in the Marine Corps,” Taylor said. “I got to pick what job I wanted.” Working as a calibration technician sounded interesting – a job that would require him to conduct testing for proper operation of a wide range of mechanical and electronic devices and tools. But before working in calibration, he’d have to go school for a year.

“Ironic, I know,” Taylor said, smiling. “I had to sign up for an extra year, so I ended up doing a five-year tour in the Marines.”

He spent most of that time working out of Camp Pendleton in California, but was deployed to Helmand Province, Afghanistan, from March through September 2010, at the height of the surge of U.S. troops. “I wasn’t a combat guy,” Taylor said. “But even on base, sometimes, the rockets would come in the middle of the night.”

Nearing the end of his enlistment in 2012, Taylor was getting the hard sell to stay in and make the Marines a career. By now, he had decided he was ready for college, but the career planner he met with tried hard to talk him out of it, predicting that Taylor would “fail again.”

“He actually told me if I got out of the Marine Corps and went back to college, I’d end up living under a bridge,” Taylor said, shaking his head. It just made him more determined to succeed.

He started back at community college, and this experience was very different. “It seemed like it was so hard the first time,” Taylor said. “What then seemed like a monumental task, now seemed like nothing. I started thinking, I might be able to do school, now.”

And he started thinking about SMU. Taylor’s grades at Collin County Community College were good – good enough to get him into his father’s alma mater.

SMU Prof’s mentoring made all the difference
Taylor never dared to think he could live up to what his Dad had accomplished, starting with the scholarship to attend SMU that Jim Taylor ’89 had received from Texas Instruments. “He was a technician there,” Taylor recalled, “and they paid for him to come here. As a kid, if you’d told me I could do something like that, too, I’d never have believed you. For me there was Albert Einstein, and Jim Taylor.”

Michael Taylor came to the Hilltop on the GI Bill, and SMU’s Yellow Ribbon program for military veterans covered what the GI Bill didn’t. Then, the Darwin Deason Institute for Cyber Security picked up the cost of his master’s degree.

Taylor’s first semester at SMU’s Lyle School was a tough adjustment after his relatively easy path at community college, but that class with professor Thornton his second semester changed everything. “Dr. Thornton offered me a position working in the Deason Institute for Cyber Security,” Taylor said. “It’s been going great since then.”

Thornton’s influence and mentoring made all the difference for Taylor.

“If I had not met Dr. Thornton, there were times I wondered if I would have gotten my bachelor’s degree. I definitely wouldn’t be getting the master’s degree. And a Ph.D. wouldn’t have been something I ever considered.”

Compelled to dive into quantum computing and cyber security
Taylor was interested in computer hardware when he arrived at SMU, but the Deason Institute opened the door to the contributions he could make in cyber security. He received the Lyle School’s 2017 Rick A. Barrett Memorial Award for outstanding work in computer science and engineering. And as he neared the completion of his master’s degree, he was tapped for the Raytheon Cyber Elite Graduate Fellowship and is looking forward to pursuing his Ph.D. in quantum computing.

“Quantum computers solve problems that are too difficult for classical computers to solve,” Taylor said. “Certain problems in classical computation are intractable, there’s no way you can solve them in this lifetime. It’s only a matter of time before quantum computers render all encryption obsolete.”

For Fred Chang, executive director of SMU’s Deason Institute and former research director for the National Security Agency (NSA), finding talented students like Taylor to fill the gaps in the cyber security workforce is “job one.” Chang testified before a congressional subcommittee in September that we are likely facing a worldwide shortage of cyber security workers five years from now.

“Today’s students will be responsible for designing, creating, operating, maintaining and defending tomorrow’s cyber infrastructure,” Chang explained. “We need a large and capable pool of folks to staff these positions for the future.”

For Taylor, cyber security is just plain compelling.

“I just like the challenge. There’s somebody out there that’s trying to crack what you have, to break you down. You have to be smarter than them. It’s a game!” — Kim Cobb, SMU

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Prehistoric puzzle settled: carbon dioxide link to global warming 22 million years ago

The modern link between high carbon dioxide levels and climate change didn’t appear to hold true for a time interval about 22 million years ago; but now a new study has found the link does indeed exist.

Fossil leaves from Africa have resolved a prehistoric climate puzzle — and also confirm the link between carbon dioxide in the atmosphere and global warming.

Research until now has produced a variety of results and conflicting data that have cast doubt on the link between high carbon dioxide levels and climate change for a time interval about 22 million years ago.

But a new study has found the link does indeed exist for that prehistoric time period, say researchers at Southern Methodist University, Dallas.

The finding will help scientists understand how recent and future increases in the concentration of atmospheric carbon dioxide may impact the future of our planet, say the SMU researchers.

The discovery comes from new biochemical analyses of fossil leaves from plants that grew on Earth 27 million years ago and 22 million years ago, said geologist Tekie Tesfamichael, lead scientist on the research.

The new analyses confirm research about modern climate — that global temperatures rise and fall with increases and decreases in carbon dioxide in our atmosphere — but in this case even in prehistoric times, according to the SMU-led international research team.

Carbon dioxide is a gas that is normally present in the Earth’s atmosphere, even millions of years ago. It’s dubbed a greenhouse gas because greater concentrations cause the overall temperature of Earth’s atmosphere to rise, as happens in a greenhouse with lots of sunlight.

Recently greenhouse gas increases have caused global warming, which is melting glaciers, sparking extreme weather variability and causing sea levels to rise.

The new SMU discovery that carbon dioxide behaved in the same manner millions of years ago that it does today has significant implications for the future. The finding suggests the pairing of carbon dioxide and global warming that is seen today also holds true for the future if carbon dioxide levels continue to rise as they have been, said Tesfamichael.

“The more we understand about the relationship between atmospheric carbon dioxide concentrations and global temperature in the past, the more we can plan for changes ahead,” said Tesfamichael, an SMU postdoctoral fellow in Earth Sciences.

“Previous work reported a variety of results and conflicting data about carbon dioxide concentrations at the two intervals of time that we studied,” he said. “But tighter control on the age of our fossils helped us to address whether or not atmospheric carbon dioxide concentration corresponded to warming — which itself is independently well-documented in geochemical studies of marine fossils in ocean sediments.”

The researchers reported their findings in Geology, the scientific journal of the Geological Society of America. The article is “Settling the issue of ‘decoupling’ between atmospheric carbon dioxide and global temperature: [CO2]atm reconstructions across the warming Paleogene-Neogene divide.”

Co-authors from the Roy M. Huffington Department of Earth Sciences in Dedman College are professors Bonnie Jacobs, an expert in paleobotany and paleoclimate, and Neil J. Tabor, an expert in sedimentology and sedimentary geochemistry.

Other co-authors are Lauren Michel, Tennessee Technological University; Ellen Currano, University of Wyoming; Mulugeta Feseha, Addis Ababa University; Richard Barclay, Smithsonian Institution; John Kappelman, University of Texas; and Mark Schmitz, Boise State University.

Discovery of rare, well-preserved fossil leaves enables finding
The findings were possible thanks to the rare discovery of two sites with extraordinarily well-preserved fossil leaves of flowering plants from the Ethiopian Highlands of eastern Africa.

Such well-preserved fossil leaves are a rarity, Tesfamichael said.

“Finding two sites with great preservation in the same geographic region from two important time intervals was very fortunate, as this enabled us to address the question we had about the relationship between atmospheric carbon dioxide concentration and global temperatures,” he said.

Scientists know that variations in the concentration of atmospheric carbon dioxide affect carbon fixation in leaves during photosynthesis. This causes leaves to develop anatomical and physiological changes such as the frequency and size of stomata — the pores on the surface of a leaf through which carbon passes.

Scientists can measure those attributes, among others, in fossil leaves, so that leaf fossils can be used as proxies for Earth’s atmospheric carbon dioxide history.

The sites producing the leaves for the SMU study were discovered separately in years past, but major fossil collections were produced through field work coordinated by the SMU research team and their co-authors, who have been collaborating on this project for several years.

The work has had funding from the National Science Foundation, The National Geographic Committee for Research and Exploration, the SMU Ford Fellowship Program, SMU Research Council, the Institute for the Study of Earth and Man, and the Dallas Paleontological Society Frank Crane Scholarship.

The fossils are housed permanently in the collections at the National Museum of Ethiopia in Addis Ababa. Institutional and governmental support came from the National Museum of Ethiopia, the Authority for Research and Conservation of Cultural Heritage, and Addis Ababa University.

Previous studies firmly established a temperature difference
One of the sites dates to the late Oligocene Epoch, and the other to the early Miocene.

Previous studies that measured ocean temperatures from around the world for the two intervals have firmly established a temperature difference on Earth between the two times, with one much warmer than the other. So the SMU study sought to measure the levels of carbon dioxide for the two time periods.

For the SMU analyses, fossil leaves of a single species were collected from the 27 million-year-old late Oligocene site. The leaves had been deposited during prehistoric times in the area of Chilga in northwest Ethiopia most likely at a river bank. The Earth’s climate during the late Oligocene may have been somewhat warmer than today, although glaciers were forming on Antarctica. The SMU study found carbon dioxide levels, on average, around 390 parts per million, about what it is on Earth today.

Fossil leaves of the 22 million-year-old species from the early Miocene were collected from ancient lake deposits, now a rock called shale, from the modern-day Mush Valley in central Ethiopia. The early Miocene climate at that time was warmer than the late Oligocene and likewise the SMU study found higher carbon dioxide levels. Atmospheric carbon dioxide was about 870 parts per million, double what it is on Earth today.

The SMU study confirmed a relationship between carbon dioxide and temperature during the late Oligocene and early Miocene.

Paleoclimate data can help predict our planet’s future climate
While carbon dioxide isn’t the only factor affecting Earth’s climate or global mean temperature, it is widely considered by scientists among the most significant. Much is known about climate change and global warming, but questions still remain.

“One of those is ‘What’s the sensitivity of the Earth’s temperature to carbon dioxide concentration? Is it very sensitive? Is it not so sensitive?’ Estimating temperature and carbon dioxide concentrations for times in the past can help find the answer to that question,” Jacobs said. “There’s a lot of work on paleoclimate in general, but not as much on the relationship between carbon dioxide and temperature.”

The finding is an important one.

“The amount of temperature change during this interval is approximately within the range of the temperature change that is estimated from climate models for our next century given a doubling of carbon dioxide concentration since the industrial revolution,” Jacobs said.

With the new model reaffirming the prehistoric relationship, scientists can look now at related questions, said climate change scientist Lauren Michel, who worked on the study as a post-doctoral researcher at SMU.

“Answering questions about the rate of change and which factors changed first, for example, will ultimately give a clearer picture of the Earth’s climate change patterns,” Michel said. “I think it is valuable to understand the relationship of greenhouse gases and climate factors represented in the rock record so we can have a better idea of what we can expect in the future and how we can prepare for that.”

SMU study confirms relationship that previous methods overlooked
Previous studies found little to no correlation between temperature and carbon dioxide for the late Oligocene and early Miocene. That has puzzled paleoclimate researchers for at least a decade.

“We have a good test-case scenario with these well-preserved plants from both time slices, where we know one time slice, with higher levels of carbon dioxide, was a warmer climate globally than the other,” Tesfamichael said.

“It’s been a puzzle as to why the previous methods found no relationship, or an inverse correlation,” he said. “We think it’s for lack of the well-dated proxy — such as our fossil leaves from two precise times in the same region — which deliver a reliable answer. Or, perhaps the models themselves needed improvement.”

Previous studies used methodologies that differed from the SMU study, although all methods (proxies) incorporate some aspects of what is known about living organisms and how they interact with atmospheric carbon dioxide.

Some studies rely on biochemical modeling of the relationship between single-celled marine fossils and atmospheric carbon dioxide, and others rely on the relationship between stomata and atmospheric carbon dioxide concentration observed in the living relatives of particular fossil plant species.

“Each method has its assumptions,” said Tesfamichael. “We will see if our results hold up with further studies of this time interval using the same methodology we used.” — Margaret Allen, SMU

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SMU Dark Matter Day celebration culminates in a dark matter rock hunt on Halloween

“In the spirit of science being a pursuit open to all, we are excited to welcome all members of the SMU family to become dark matter hunters for a day.” — SMU physicist Jodi Cooley

This Halloween, people around the world will be celebrating the mysterious cosmic substance that permeates our universe: dark matter.

At SMU, the Department of Physics in Dedman College of Humanities and Sciences is hosting a Dark Matter Day celebration, and students, faculty, staff and DFW residents are invited to join in the educational fun with events open to the public.

To kick off the festivities, two speaking events by scientists in the field of dark matter will familiarize participants with the elusive particles that scientists refer to as dark matter. The first talk is oriented toward the general public, while the second is more technical and will appeal to people familiar with one of the STEM areas of science, technology, engineering or mathematics, particularly physics and astrophysics.

Then throughout Halloween day, everyone is invited to test their skills at finding dark matter — in this case, a series of rocks bearing educational messages related to dark matter, which the Society of Physics Students has painted and then hidden around the campus.

Anyone lucky enough to find one of the 26 rocks can present it at the Physics Department office to receive a prize, says SMU physics professor Jodi Cooley, whose research is focused on the scientific challenge of detecting dark matter.

“In the spirit of science being a pursuit open to all, we are excited to welcome all members of the SMU family to become dark matter hunters for a day,” Cooley said. “Explore your campus in the search for dark matter rocks, just as physicists are exploring the cosmos in the hunt for the nature of dark matter itself.”

Anyone who discovers a dark matter rock on the SMU campus is encouraged to grab their phone and snap a selfie with their rock. Tweet and tag your selfie #SMUDarkMatter so that @SMU, @SMUResearch and @SMUPhysics can retweet photos of the lucky finders.

As SMU’s resident dark matter scientist, Cooley is part of the 100-person international SuperCDMS SNOLAB experiment, which uses ultra pure materials and highly sensitive custom-built detectors to listen for the passage of dark matter.

SuperCDMS, an acronym for Super Cryogenic Dark Matter Search, resides at SNOLAB, an existing underground science laboratory in Ontario, Canada. Located deep underground, SNOLAB allows scientists to use the earth as a shield to block out particles that resemble dark matter, making it easier to see the real thing.

The SuperCDMS SNOLAB experiment, expected to be operational in 2020, has been designed to go deeper below the surface of the earth than earlier generations of the research.

“Dark matter experiments have been a smashing success — they’ve progressed farther than anyone anticipated. The SuperCDMS SNOLAB experiment is quite unique,” Cooley said. “It will allow us to probe models that predict dark matter with the tiniest masses.”

For more on Cooley’s research, go to “Hunt for dark matter takes physicists deep below earth’s surface, where WIMPS can’t hide.“ — Margaret Allen, SMU

Dark Matter Day events at SMU:

  • Sunday, Oct. 29, 4 p.m., McCord Auditorium — Maruša Bradač, Associate Professor at the University of California at Davis, will give a public lecture on dark matter. A reception will follow the lecture from 5 p.m. to 6 p.m. in the Dallas Hall Rotunda with beverages and light snacks. This event is free and open to the public, and is designed to be open to the widest possible audience.
  • Monday, Oct. 30, 4 p.m., Fondren Science Building, Room 158 — SMU Associate Professor Jodi Cooley will present a seminar on the SuperCDMS direct-detection dark matter search experiment. This event is part of the Physics Department Speaker Series. While this event is open to the public, it will be a more technical talk and may appeal more to an audience interested in the STEM areas of science, technology, engineering and mathematics, especially physics and astrophysics.
  • Tuesday, Oct. 31, 9 a.m. – 4 p.m., SMU Main Campus, Dark Matter Rock Hunt — The SMU Department of Physics has hidden “dark matter rocks” all across the SMU main campus. If you discover one of the dark matter rocks, bring it to the main office of the Physics Department, Fondren Science Building, Room 102, and get a special prize. All SMU students, faculty, staff and community members are welcome to join in the search.