News and Updates


Combining his love for 3-D animation, space and engineering, Sean Amidan has turned a hobby into a career opportunity.

Amidan, a senior earth and space exploration major with a concentration in systems design, is the lead visualization specialist at the Space and Terrestrial Robotic Exploration Laboratory (SpaceTREx) at Arizona State University.

He spends his days creating and designing 3-D models of CubeSats (miniature satellites) for the Asteroid Origins Satellite (AOSAT) project, designing logos for the School of Earth and Space Exploration outreach programs and developing 3-D visualization software.

“The professor I work for (Jekan Thanga) is in charge of the whole lab, and I know he has done a few things [with] the International Space Station, so that’s cool,” Amidan said. “Some of the professors I’ve had in my classes have worked on Hubble, the space telescope … and now I’m working with [them].”

Amidan discovered his skill for 3-D animation in high school when he took two years of 3-D animation classes, but never envisioned it carrying through into college. He started off at ASU on the pre-med track, then decided to try out engineering before he finally settled in at School of Earth and Space Exploration after accepting a job in the SpaceTREx lab.

“It was more kind of a hobby so I started to do different stuff in college but then I got lucky and found this job working for the lab,” Amidan said.

Along with his 3-D animation work in the lab, Amidan also gets to explore the software, programming and robotics elements of the space program in his classes, which, in turn, often informs his work in the lab.

“My degree really helps in the lab because I can really understand why [something is] being built this way, or what it’s being built for,” Amidan said. “It would be really hard to do the 3-D modeling without my degree and that knowledge.”

Amidan’s favorite project so far has been the AOSAT CubeSats. A CubeSat is a small, modular satellite, about the size of a loaf of bread. Amidan is designing the artistic renderings for the project, helping to bring the concept to life, with the guidance of his professor and NASA experts.

Currently in his last semester at ASU, Amidan is looking toward the future and has already started to apply for jobs after graduation. If he had to pick his dream job, the monthly magazine Popular Science would be at the top of his list.

“I joke around with people saying that I want to work at Popular Science and do all their artwork and science models. I think that would be pretty fun,” Amidan said.

Back at the lab, Amidan is continuing to create artist renderings of the CubeSat, and will continue to make tweaks as the project grows.

The ASU CubeSat is expected to be flight-ready by May 2016.

Written by Samantha Pell, ASU News

Photo: ASU student Sean Amidan created this concept art for a small highly energy efficient robot. The earth and space exploration senior is the lead visualization specialist at the Space and Terrestrial Robotic Exploration Laboratory at Arizona State University.
Photo by: Sean Amidan


An article assistant professor Christy Till wrote with a colleague was just posted on the American Geophysical Union, Volcanology, Geochemistry and Petrology (VGP) website and can be found here:

Amongst the discussion of exciting research topics, the article features descriptions and pictures of Till's laboratory and research group in SESE, which focuses on the study magma and how and why it forms in the lab under simulated high pressures and temperatures, and what that tells us about planetary differentiation. A more detailed explanation can be found on her lab website:



Come learn about the huge diversity of life as we know it, life as we think it might be, and how we're trying to discover it on other worlds at the next Earth and Space Open House, March 27.

Is there alien life beyond planet Earth? We don't yet know, and the job of astrobiologists — those who study life in space — is to find out.

One place to start the search is within our own solar system, where hunting for life is like looking for a good restaurant. There are three kinds of places: the chain franchises (decent, but so predictable), the up-and-coming areas (the next big thing), and the hidden gems (hit or miss, but could be amazing). Come find out about the must-go places in the Yelp of astrobiologists.

Those who wish to learn more about extraterrestrial life are invited to attend a free public lecture at the next Earth and Space Open House, from 7 to 10 p.m., March 27, at the Interdisciplinary Science and Technology Building IV (ISTB 4) on ASU’s Tempe campus.

The talk, "Hunting for Life in the Solar System," will be given by the School of Earth and Space Exploration's Marc Niveu, graduate student in astrophysics.

In addition to the public talk, there will be two 3-D planetarium shows in the Marston Exploration Theater, at 7:15 and 8:45 p.m. All seating is on a first-come basis.

At 8 p.m., attendees can "Create Your Own Planet" in the Marston Exploration Theater. (Participants must sign up at the welcome table beforehand.)

As usual, there will be telescope sky viewing outdoors next to the James Turrell Skyscape art installation from 8 to 10 p.m. (weather permitting). There will also be several exciting demonstrations and activities in the state-of-the-art ISTB4 Gallery of Scientific Exploration by experts in astrobiology, geology, cosmology and planetary science – as well as a free poster.

The open house can be accessed through the main entrance of ISTB 4, located on the building’s north side.

The monthly open house is sponsored by the School of Earth and Space Exploration, GeoClub, AstroDevils: ASU Astronomy Club, Icarus Rocketry, Students for the Exploration and Development of Space (SEDS), the Center for Meteorite Studies (CMS) and many others.

For more information, visit or visit the school's Facebook event page. The final open house of the spring semester will be held on April 24 (on the 25th anniversary of the Hubble Space Telescope).

The School of Earth and Space Exploration is an academic unit of the College of Liberal Arts and Sciences.


The moon is pelted with cosmic debris all the time, but the largest explosion on its surface that we’ve actually recorded occurred two years ago today. On March 17, 2013, an object the size of a small boulder hit the surface in Mare Imbrium and exploded in a flash of light nearly 10 times as bright as anything ever recorded before.

Images acquired of the surface before and after the impact by NASA’s Lunar Reconnaissance Orbiter Camera (LROC), overseen by a team at Arizona State University, reveal intricate details of the resulting impact crater and help calibrate models of crater formation.

Since 2005, astronomers have monitored the moon for signs of explosions caused by meteoroids hitting its surface. When a meteoroid strikes the moon, a large portion of the impact energy goes into heat and excavating a crater; however, a small fraction goes into generating visible light, which results in a brilliant flash at the point of impact.

The brightest flash recorded by researchers at NASA’s Marshall Space Flight Center occurred on March 17, 2013 with coordinates 20.6°N, 336.1°E. The team predicted the crater’s size based on the energy, and they eagerly awaited LROC’s next pass over the location to confirm their calculations.

Being able to get observations before, during and after the impact is a valuable opportunity to understand impact events better. Comparing the actual size of the crater to the brightness of the flash helps validate impact models.

The hunt for the March 17 crater

LROC’s first set of post-impact flash images acquired on May 21, 2013 by the Narrow Angle Camera were targeted on the Marshall-reported coordinates and numerous small surface disturbances (“splotches”) were detected by comparing the pre- and post-flash images, but no new crater was found.

A second set of Narrow Angle Camera images was acquired on July 1, 2013, showing three faint ray-like features and several chains of splotches and asymmetric splotches that generally pointed to a common area west of the Marshall coordinates. A Narrow Angle Camera pair was targeted on that convergence point for July 28, 2013; comparison of this third set of images with preexisting coverage revealed a new crater.

The crater itself is small, measuring 18.8 meters (61.7 feet) in diameter, but its influence large; debris excavated by the sudden release of energy flew for hundreds of meters. More than 200 related surficial changes up to 30 kilometers (19 miles) away were noted.

Not only did the LROC images reveal intricate details of ejecta distribution, but they also offered a valuable opportunity to study the structure of the top meter of the regolith. Regolith is a term that refers to a soil that is lacking organic material.

The soil on the Moon is formed slowly over time as micrometeorites impact the surface and slowly grind rocks into a fine powder. As the fresh soil grains sit on the surface they are exposed to radiation and slowly become darker and redder (mostly due to reduction of iron in minerals to iron metal – reverse of rusting that happens on Earth). This slow change in reflectance and color is generally referred to as space weathering; fresh soil is referred to as immature, and weathered soil is mature. The longer a soil sits on the surface the more mature it becomes.

Several surprises were revealed in the before and after image pairs around the new crater. Conventional thought predicted that the new crater should be surrounded by a high reflectance ejecta blanket out to about a crater diameter with some patchy ejecta spreading out two or three diameters.

“The high reflectance was there, but three other zones were discovered. At the edge of the high reflectance ejecta was a low reflectance zone, then beyond that another high reflectance zone and beyond that another low reflectance zone,” reports Mark Robinson, a professor in ASU’s School of Earth and Space Exploration and LROC’s principal investigator.

The results are published are in the Jan. 31 edition of the journal Icarus.

Finding new impact craters

It’s not easy to find new impact craters because most of them are very small. The only way to really do this is to have a before image and an after image to compare.

LROC began systematically mapping the Moon in the summer of 2009. Now, the team is going back to images taken in the first year or two and comparing them to recent images. Called temporal pairs, these before/after images enable the search for a range of surface changes, including new impact craters, formed between the time the first and second image were acquired.

As of Jan. 1, 2015, LROC has acquired about 10,000 before and after image pairs. Manual scanning of all these pairs is impractical so Robinson’s team developed a computer program that automatically identifies suspected changes from each temporal pair.

With the help of the automated tool, the team has identified 225 new impact craters ranging in size from 1.5 meters to 43 meters (4.9 feet to 140 feet) and over 25,000 small changes known as “splotches” (likely unresolved primary and secondary craters).

Image: Four different NAC images of crater (18 meter diameter) formed on the moon, March 17 2013, each scene is 560 meters wide, north is up.
Photo by: NASA/GSFC/Arizona State University

(Nikki Cassis)



The Origins Project at Arizona State University awarded its first Postdoctoral Prize Lectureship to Adrian Liu of the University of California, Berkeley. The award, the largest of its kind in the world, is in recognition of Liu’s groundbreaking early career work in exploring the astrophysics of the early universe. It includes a $10,000 prize.

As part of the Origins Project postdoctoral prize lectureship, Liu will spend a week in Tempe in April and will deliver three colloquia and a public talk on his research. He will also take part in an awards ceremony and other Origins activities.

Liu is a Berkeley Center for Cosmological Physics postdoc currently working on 21 cm (hydrogen line) tomography measurements of the early universe. His research focuses on understanding how our Universe came to be what it is today by looking at how hydrogen is distributed in space and time.

“Adrian Liu is the perfect inaugural Origins Project Postdoctoral Prize Lecturer,” said Lawrence Krauss, director of the Origins Project at ASU. “Chosen from among 50 distinguished nominees from premier research institutions around the world, he stood out both for the quality of his research and for his superb ability to communicate it.”

“Adrian is already the recipient of prestigious fellowships in his field, including a Hubble fellowship,” Krauss added. “Moreover, he is exploring an emerging frontier in astrophysics that promises to shed light on the origin of all the cosmic structures we see today, from clusters of galaxies on downward, and thus to our own cosmic origin. And if that weren’t enough, he is a superb communicator. For example, he was the first person to get a perfect teaching score in the large courses he helped teach while a graduate student at MIT. It couldn’t be a better beginning for a world-class annual prize series focusing on Origins research.”

“It’s an absolute honor to be chosen for the Origins Project’s Postdoctoral Prize Lectureship,” Liu said. “In astrophysics our interests and goals are closely aligned to those of the Origins Project, in that we seek to understand how our Universe works, and where the awe-inspiring astronomical structures that we see today came from. I’m particularly grateful for the opportunity to share my work with audiences at ASU, who will see that rather than being a solved problem, the question of our origins is an exhilarating journey that continues to fascinate scientists today.”

“I’m trying to understand how our universe came to be the way it is,” Liu explained. “For instance, what was the nature of the first galaxies? In what ways are they different from what we see today? How did they form? One way to answer questions like these is to make really, really good maps of how hydrogen is distributed in our Universe. Once we have that, we can work backwards and figure out how our Universe came to be what it is today by studying how the state and distribution of hydrogen changed over our cosmic history.”

Liu graduated from Princeton University summa cum laude with a Bachelor’s degree in Physics in 2006. He then attended the Massachusetts Institute of Technology, obtaining his Ph.D. in 2012. His dissertation, advised by Prof. Max Tegmark, was titled “From theoretical promise to observational reality: calibration, foreground subtraction, and signal extraction in hydrogen cosmology.”

Liu has earned multiple teaching awards while a graduate student at MIT, including the Buechner Teaching Prize, the Henry Kendall Teaching Award and the Goodwin Teaching Medal.

The Origins Project postdoctoral prize lectureship is the largest of its kind in the world for postdoctoral researchers. The prize is an annual worldwide competition for the best junior scholar chosen from all countries in any field of study relevant to the Origins Project. Krauss noted that in its first year, the competition drew interest worldwide in fields including astrophysics, biology, geology, planetary science, history and medical engineering.

“Postdoctoral researchers are the young scholars who most often are behind the groundbreaking discoveries of tomorrow, but they are not often recognized until they are in more senior positions,” Krauss said. “We wanted to provide a significant world-wide recognition for this under appreciated community, who will become the leaders of the next generation, and at the same time bring these exciting scholars to ASU to interact with our faculty and students and perhaps forge long-term partnerships. In doing so we will continue to enhance the mission of the Origins Project to promote new forefront investigations of foundational questions, and also expose the university and the public to the most exciting research being done in the world today."

For more information on the award, go to:

(Skip Derra)



U.S. News & World Report today released the 2016 Best Graduate Schools rankings. Arizona State University’s School of Earth and Space Exploration holds its rank among the top 20 graduate schools in the country.

The publication’s recently released list ranks ASU’s Earth Sciences program 20th among public and private graduate programs, making it the highest ranking science program at ASU. More than 100 earth sciences graduate programs were surveyed, with rankings based on the results of questionnaires sent to department heads and directors of graduate programs.

Tied for 20th, the rankings overall put ASU on par with earth sciences graduate programs at University of California, Davis and University of Chicago.


A self-described introvert, Kali Johnson isn’t necessarily comfortable on stage.

But that’s exactly where the 25-year-old Arizona State University student found herself – in front of a panel of judges during the Great SESE Pitching Competition. Johnson was pitching an idea for a student organization that will create support systems for ASU students who are also parents to help them succeed.

The competition, organized by ASU’s School of Earth Sciences and Exploration (SESE) with support from ASU’s Office of Entrepreneurship and Innovation, is one of a growing number of efforts across the university to encourage entrepreneurial thinking in ASU graduate and undergraduate students, including students who don’t necessarily see entrepreneurship as a career goal. Two winners – first place and audience favorite – were selected from undergraduate as well as graduate student categories, and won a total of $3,000 in prize money.

The idea for the competition is the brainchild of Lindy Elkins-Tanton, director of the School of Earth Sciences and Exploration. According to her, the traditional approach of educating students, especially those pursuing graduate degrees, leaves much to be desired.

“While we’re doing a wonderful job of training our students to be brilliant researchers, we need to start teaching them other useful life skills, such as the ability to pitch an idea, to speak compellingly to others, to negotiate and write budgets, etc., that will take our students to the next level,” she said.

Elkins-Tanton decided to tackle this problem. First, she enlisted the support of SESE faculty members and Mitzi Montoya, vice president and university dean of entrepreneurship and innovation at ASU. Montoya funded the two first prizes and found Elkins-Tanton pitching trainers to help graduate students hone their pitches and communicate their ideas effectively to the judges and the audience.

“Our graduate students then trained our undergraduate students, using the expert advice they’d just received,” she said. “The peer-to-peer mentoring was very effective in helping our incoming freshmen think about education and their college experience in a different way.”

Entrepreneurial spirits

Kali Johnson, a sophomore majoring in astrobiology and biogeosciences, first joined ASU in 2007 but had to drop out a year later because of health reasons. Determined to stay on path, she went on to get her associate’s degree in arts and worked in retail for a few years. Then came the turning point: She gave birth to her daughter.

“I didn’t want her to think that I gave up too easily on my dreams, so I came back to ASU to earn my degree,” she said. “However, I quickly realized that I needed more support in terms of information, networking and scholarship opportunities to finish my degree, especially as a young parent, and thought this was an opportunity to create something that will outlast my time at ASU.”

Johnson pitched the idea for the Proud Parent Scholarship Fund at the Great SESE Pitching Competition and won $500 as part of the audience’s choice award in the undergraduate category. Kevin Conklin, an astrophysics junior, won the first place and $1,000 to fund his venture: a weekly podcast called ASU Connections that aims to educate, entertain and attract people to scientific research and scientists at ASU.

“I decided to join ASU to earn my college degree after listening to a podcast featuring ASU planetary scientist and astronomer Jim Bell talking about the Mars Curiosity Rover and his involvement in the project, which blew me away,” said Conklin. “Through the ASU Connections podcast, I’d like to build a brand of educated people who take their science seriously but also like to have fun with it.”

Combining research and entrepreneurial ideas

According to Elkins-Tanton, while most undergraduate students focused on ideas that were inspired by academic disciplines, graduate and doctoral students pitched ideas for research projects on earth sciences-related topics.

Abhijith Rajan, a doctoral student of astrophysics at SESE and first prize winner in the graduate student category, proposed hosting a two-day Software Carpentry workshop at ASU that teaches students to be efficient software programmers and, consequently, better researchers. Software Carpentry is a nonprofit organization whose members teach researchers basic programming skills. Rajan hopes to launch the program in the summer and make it self-sustaining.

“We have identified local resources, including students in the department, who will teach sections to help make the program more affordable and, going forward, completely free for the department,” he said.

Jean François-Smekens, another SESE doctoral student who won the audience choice award in the graduate student category and a sum of $500, pitched an idea that turns a sulfur dioxide camera – digital cameras that monitor sulfur dioxide emissions during volcanic activity – into a practical tool for volcano monitoring.

Mitzi Montoya, vice president and university dean of entrepreneurship and innovation at ASU, views the Great SESE Pitching Competition as an example of a larger culture change underway ASU.

“At ASU, we are creating a pipeline of graduates who think differently,” said Montoya. “Programs like SESE inspire students to do something out of their comfort zone. This exposure to new ways of thinking and problem-solving helps develop an entrepreneurial mindset that is needed to succeed in any field. Programs like this show ASU’s university-wide commitment to fostering entrepreneurial and innovative ASU students in all academic disciplines.”

Image: ASU School of Earth and Space Exploration student Natalie Hinkel pitches her idea for The Science Bar Podcast at the Great SESE Pitching Competition.

(Iti Agnihotri)


Timmes to go on research leave to explore stellar explosions and cosmic chemical evolution

The Simons Foundation, which is dedicated to advancing math and science research, will give an Arizona State University astrophysicist the opportunity to spend a year away from classroom and administrative duties to pursue research interests.

This year’s group of Simons Fellows includes ASU’s Francis (Frank) Timmes, a professor in the School of Earth and Space Exploration and ASU's director of Advanced Computing.

Timmes is an astrophysicist interested supernovae, cosmic chemical evolution, astrobiology, the gamma-ray astronomy, and high performance computing. His Simons Fellowship in Theoretical Physics award will let him focus on research for the 2015-16 academic year.

Timmes plans to use his academic year sabbatical to advance his research activities: (1) a NASA funded Theoretical and Computational Astrophysics Networks (TCAN) project aimed at exploring the internal structure and evolutionary histories of supernova progenitors; (2) an NSF funded Software Infrastructure for Sustained Innovation (SI2) project aimed at supporting the Modules for Experiments in Stellar Astrophysics (MESA) software instrument; and (3) within the Joint Institute for Nuclear Astrophysics – Center for the Evolution of the Elements (JINA-CEE), an NSF funded Physics Frontier Center.

“I am very excited about the opportunity provided by the Simons Fellowship. It will give me the time and flexibility to pursue leading-edge research with colleagues as research projects unfold,” said Timmes, who plans to visit the Kavli Institute for Theoretical Physics at University of California Santa Barbara, as well as experts in nuclear astrophysics at Michigan State University and the University of Notre Dame.

Research leaves from classroom teaching and administrative obligations can provide strong intellectual stimulation and lead to increased creativity and productivity in research. The Simons Fellows program is intended to make leaves more productive by enabling the extension of sabbatical leaves from one academic term to a full academic year.

Simons Fellows are chosen based on research accomplishment in the five years prior to application and the potential scientific impact of the fellowship.

“I feel fortunate because very few organizations fund sabbatical research in Theoretical Physics,” Timmes said of the award. “I am grateful to the Simons Foundation for their support of our field.”

Timmes is one of only 14 scholars to receive the award for theoretical physics. Timmes accompanies professors from other top universities and colleges in the United States such as Harvard, Cornell and Massachusetts Institute of Technology, to name a few. He is ASU’s first Simons Fellow.

The Simons Foundation is a private foundation based in New York City, incorporated in 1994 by Jim and Marilyn Simons. Its mission is to advance the frontiers of research in mathematics and the basic sciences by sponsoring a range of programs that aim to promote a deeper understanding of our world. The Simons Foundation Mathematics and Physical Sciences division, established in 2010, supports research in mathematics, theoretical physics and theoretical computer science and provides funding for individuals, institutions and science infrastructure, including the Simons Fellows.

Image: With his Simons Fellowship, Frank Timmes will conduct forefront research on stars using advanced computing instruments and tools.

(Nikki Cassis)



Infrared and visual images of the Martian surface taken by Arizona State University's THEMIS camera are mapping dust and rocks at the landing site for NASA's upcoming InSight mission to Mars.

NASA's next Mars space probe, a lander named InSight, is due to touch down on the Red Planet in September 2016 with a mission focused on the planet's internal properties. Its landing place has been chosen with help from a Mars-orbiting, heat-sensitive camera designed and operated at Arizona State University.

THEMIS maps of InSight landing ellipse, as seen in daytime infrared (top) and night.Working at nine infrared and five visual wavelengths, the Thermal Emission Imaging System (THEMIS) on NASA's Mars Odyssey orbiter has been in operation since early 2002. Its data have let scientists create a near-global map of Martian surface properties.

More recently, THEMIS has been surveying the rocks, sand, dust and surface materials across InSight's four candidate landing areas. NASA has now picked as the prime landing site one location in Elysium Planitia, a region where ancient lava flows cover the ground.

"To land a probe safely on Mars, you need to come down in a flat, smooth place," said Jonathon Hill, of Arizona State University's Mars Space Flight Facility, part of ASU's School of Earth and Space Exploration. A staff member and doctoral student in planetary science, Hill has a day-to-day role in targeting specific areas of Mars for THEMIS to image.

"Picking a safe place," he said, "means the landing site can't be full of big rocks or covered in a thick layer of dust."

By measuring how quickly the ground cools at night or warms in sunlight, THEMIS can tell the proportion of rocks and dust on the ground and thus help paint a picture of what awaits the lander at the surface.

InSight (short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) carries two main instruments, a heat-flow probe and a seismometer, both being deployed using a robotic arm. The heat probe requires that the ground within reach of the arm be penetrable by the probe, which will hammer itself into the soil to a depth of three to five yards, or meters.

"InSight's mission planning team worked closely with us to find places with a suitable surface for the spacecraft to go," says Hill. Additional data and imaging came from the High Resolution Imaging Science Experiment (HiRISE) on NASA's Mars Reconnaissance Orbiter.

While THEMIS' main contribution to NASA's site choice was its infrared data, THEMIS is also currently taking visual images of the entire landing site ellipse, which represents the target zone. The visual images each cover a smaller area, but have about five times sharper resolution than the infrared ones.

Scouting ahead is old story

Checking out a Martian landing site ahead of touchdown is a now-familiar role for THEMIS, said ASU's Philip Christensen. A Regents' Professor of geological sciences in the School of Earth and Space Exploration, Christensen is the designer and principal investigator for the THEMIS camera.

"Before NASA's Curiosity Mars rover landed in Gale Crater in 2012," he said, "THEMIS surveyed the surface materials at dozens of candidate landing areas scientists were evaluating." And earlier, he noted, "THEMIS selected the landing site for NASA's Phoenix Mars probe, which landed in 2008, by mapping the rocks and dust at numerous potential sites to find the safest one."

Unlike NASA's recent Mars landers, InSight is not a rover. Built using the same flight platform as the Mars Phoenix lander, InSight will touch down in one place and stay there for its entire mission, projected to last two Earth years.

But immobility means that if InSight came down in a location that's too dusty or rocky, it wouldn't be able to drive away from the landing site and find a better location. This raised the stakes on where it lands, and that's where THEMIS has played its part.

Said Christensen, "We're delighted to help find a good landing spot for InSight. And also to be helping scientists learn more about Mars, and deepen our picture of this intriguing world next door to Earth."

The School of Earth and Space Exploration is a unit in ASU's College of Liberal Arts and Sciences. 




A fossil lower jaw found in the Ledi-Geraru research area, Afar Regional State, Ethiopia, pushes back evidence for the human genus — Homo — to 2.8 million years ago, according to a pair of reports published March 4 in the online version of the journal Science. The jaw predates the previously known fossils of the Homo lineage by approximately 400,000 years. It was discovered in 2013 by an international team led by Arizona State University scientists Kaye E. Reed, Christopher J. Campisano and J Ramón Arrowsmith, and Brian A. Villmoare of the University of Nevada, Las Vegas.

For decades, scientists have been searching for African fossils documenting the earliest phases of the Homo lineage, but specimens recovered from the critical time interval between 3 and 2.5 million years ago have been frustratingly few and often poorly preserved. As a result, there has been little agreement on the time of origin of the lineage that ultimately gave rise to modern humans. At 2.8 million years, the new Ledi-Geraru fossil provides clues to changes in the jaw and teeth in Homo only 200,000 years after the last known occurrence of Australopithecus afarensis (“Lucy”) from the nearby Ethiopian site of Hadar.

Found by team member and ASU graduate student Chalachew Seyoum, the Ledi-Geraru fossil preserves the left side of the lower jaw, or mandible, along with five teeth. The fossil analysis, led by Villmoare and William H. Kimbel, director of ASU’s Institute of Human Origins (IHO), revealed advanced features, for example, slim molars, symmetrical premolars and an evenly proportioned jaw, that distinguish early species on the Homo lineage, such as Homo habilis at 2 million years ago, from the more apelike early Australopithecus. But the primitive, sloping chin links the Ledi-Geraru jaw to a Lucy-like ancestor.

“In spite of lot of searching, fossils on the Homo lineage older than 2 million years ago are very rare,” says Villmoare. “To have a glimpse of the very earliest phase of our lineage’s evolution is particularly exciting.”

In a report in the journal Nature, Fred Spoor and colleagues present a new reconstruction of the deformed mandible belonging to the 1.8 million-year-old iconic type-specimen of Homo habilis (“Handy Man”) from Olduvai Gorge, Tanzania. The reconstruction presents an unexpectedly primitive portrait of the H. habilis jaw and makes a good link back to the Ledi fossil.

“The Ledi jaw helps narrow the evolutionary gap between Australopithecus and early Homo,” says Kimbel. “It’s an excellent case of a transitional fossil in a critical time period in human evolution.”

Global climate change that led to increased African aridity after about 2.8 million years ago is often hypothesized to have stimulated species appearances and extinctions, including the origin of Homo. In the companion paper on the geological and environmental contexts of the Ledi-Geraru jaw, Erin N. DiMaggio, of Pennsylvania State University (SESE Ph.D. 2013), and colleagues found the fossil mammal assemblage contemporary with this jaw to be dominated by species that lived in more open habitats—grasslands and low shrubs—than those common at older Australopithecus-bearing sites, such as Hadar, where Lucy’s species is found.

“We can see the 2.8 million year aridity signal in the Ledi-Geraru faunal community,” says research team co-leader Kaye Reed, “but it’s still too soon to say that this means climate change is responsible for the origin of Homo. We need a larger sample of hominin fossils, and that’s why we continue to come to the Ledi-Geraru area to search.”

Cross Collaboration
The collaboration between ASU anthropologists and geologists began in 2001 when Kaye Reed and Charles Lockwood were new professors in the ASU Institute of Human Origins and School of Human Evolution and Social Change. They needed a geologist to join them as they started working in a new area closer to what was thought to be the depositional center of the “Hadar” basin.

According to Professor Ramón Arrowsmith in ASU’s School of Earth and Space Exploration, “They asked if I knew anyone who might be interested and I thought about it and I said that I could give it a try. So we started the first season in January 2002. We worked for quite some time, going 2002, 2004, 2005, 2006, 2008, 2009, 2012, 2013, and 2015 so far!”

Erin DiMaggio, the first author of the paper on the geology, started with Arrowsmith working on this project in 2005. She did her Ph.D. on the topic and graduated from SESE in 2013.

While Arrowsmith was not onsite when the jaw was found, he heard the news soon after.

“About week after I had returned from being in the field with them, I received a phone call from Ethiopia early in the morning. I was worried that there was an accident or something, but actually it was Erin who was shouting and happy and said that they had found the mandible,” recalls Arrowsmith.

DiMaggio and Arrowsmith’s work was to build on the very little prior information to produce a structural and stratigraphic and temporal framework into which fossils of importance could be placed.

“The area is faulted due to regional extension pulling the Horn of Africa away to the east and Arabia away to the northeast from the rest of Africa, so we have to divide it into separate fault blocks and characterize each individually and then relate them temporally both by the basic logic of geology as well as by numerical and correlative dating of numerous volcanic deposits, known as tephra,” explains Arrowsmith. “The important point is that the sedimentary sequence represents a time period previously undocumented in the region, hence the opportunity of finding and documenting this mandible.”

The research team includes:
• Erin N. DiMaggio (Pennsylvania State University), Christopher J. Campisano (ASU Institute of Human Origins and School of Human Evolution and Social Change), J. Ramón Arrowsmith (ASU School of Earth and Space Exploration), Guillaume Dupont-Nivet (CNRS Géosciences Rennes), and Alan L. Deino (Berkeley Geochronology Center), who conducted the geological research
• Faysal Bibi (Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science), Margaret E. Lewis (Stockton University), John Rowan (ASU Institute of Human Origins and School of Human Evolution and Social Change), Antoine Souron (Human Evolution Research Center, University of California, Berkeley), and Lars Werdelin (Swedish Museum of Natural History), who identified the fossil mammals
• Kaye E. Reed (ASU Institute of Human Origins and School of Human Evolution and Social Change), who reconstructed the past habitats based on the faunal communities
• David R. Braun (George Washington University), who conducted archaeological research
• Brian A. Villmoare (University of Nevada Las Vegas), William H. Kimbel (ASU Institute of Human Origins and School of Human Evolution and Social Change), and Chalachew Seyoum (ASU Institute of Human Origins and School of Human Evolution and Social Change, and Authority for Research and Conservation of Cultural Heritage, Addis Ababa), who analyzed the hominin fossil.

Research funding was provided by the National Science Foundation (BCS-1157351, BCS-1322017, and BCS-0725122 HOMINID grant), the Institute of Human Origins at Arizona State University, the George Washington University Selective Excellence Program, AAPG, SEPM, GSA, the Philanthropic Education Organization, Marie Curie CIG, Fyssen, and HERC/UC Berkeley.

Photo of Ramon Arrowsmith and Erin DiMaggio. Photo by: Matt Jungers

(Julie Russ)