News and Updates


Experimental cosmologist Judd Bowman has been awarded a NASA Nancy Grace Roman Technology Fellowship in Astrophysics for early-career researchers. He is one of three recipients to receive this prestigious new award.

Bowman is an assistant professor in the School of Earth and Space Exploration at Arizona State University. He is an interested in the formation of structure in the early Universe, including the first stars, galaxies, and black holes.

Last fall, NASA established the Roman Technology Fellowship program to foster technologies that advance scientific investigations in the origin and physics of the universe and future exoplanet exploration. The fellowship is named after Nancy Grace Roman, a distinguished American astronomer who was instrumental in establishing the new era of space-based astronomical instrumentation. The award will support Bowman and a postdoc for a one-year concept study, with the opportunity to continue on for a three-year instrument development program.

This fellowship is well-suited to Bowman’s research interests, which focus on the development of technologies to enable observational probes of Cosmic Dawn, the period when the first stars, galaxies, and black holes are believed to have formed only a few hundred million years after the Big Bang.

“Learning how and when stars and galaxies first formed in the early Universe is central to understanding our place in the Universe today, yet it is very challenging. The first galaxies will be very difficult to see with telescopes so we are trying a different approach,” explains Bowman.

The project that Bowman proposed is to identify the best wideband radio receiver design at low radio frequencies.

“Low-frequency radio observation of the redshifted 21 cm line of neutral hydrogen is a promising technique to study the gas around the first galaxies, but we need to build radio receivers that we can calibrate 100 times better the best radio receiver used by astronomers today. That is a difficult task! We have only just begun to attempt it,” says Bowman. “The Roman Technology Fellowship will hopefully give us the jump start we need to make this technology a reality.”

Bowman and collaborators have already designed a prototype and will be traveling to Australia over spring break to test it. Stay current on the latest developments by reading posts at:

“This project very much epitomizes what SESE stands for – the melding of science and technology to promote exploration of our Universe and environment. We are pushing technological limits in ways that will likely benefit earth, atmospheric, and planetary science, as well as astronomy. In order to even get to this point, we've had to revisit and extend core equations used in electrical engineering that have been well established for over 30 years,” says Bowman.

The receiver Bowman and his collaborators will develop is part of a NASA mission concept called DARE (Dark Ages Radio Explorer) that would orbit the Moon, using the Moon as a shield to block disruptive transmissions, such as FM radio and TV stations, originating from the earth.

“We will work closely with our collaborators on DARE at JPL, University of Colorado, and the National Radio Astronomy Observatory. In particular, this fellowship will help to strengthen ties between ASU and JPL and provide opportunities for students to visit JPL and JPL scientists to come to ASU to work with students in our lab here,” says Bowman.

Bowman is principal investigator of EDGES, a ground-based pathfinder for the DARE mission concept, and is project scientist for the Murchison Widefield Array. Bowman also co-leads the DARE Calibration and Instrument Validation team and is a co-investigator of the Lunar University Network for Astrophysics Research.

(Nikki Cassis)


Again this summer, in collaboration with the American Geosciences Institute (AGI) and NASA, the School of Earth and Space Exploration is hosting a week-long Earth and Space Science Teacher Leadership Academy. Successful applicants will receive training in current NASA research and other hot topics in Earth and space sciences, abundant teaching resources, continuing education credit, and a stipend. The application deadline is Monday 30 April. Please refer to the posted flyer for details.


Mihály Pósfai, a member of the Hungarian Academy of Sciences (HAS) , arrived in Tempe last week and will be in residence as an ASU Visiting Professor during March doing microscopy research. 

In 2010, Pósfai, a former ASU scientist, was elected a member of the HAS, an organization of scientific notables that has had a long and distinguished membership reflecting the rich and fruitful scientific traditions of Hungary. Election to a National Academy of Sciences is one of the highest honors bestowed on scientists in their respective countries.

The HAS has 365 members. New members are elected every three years through an elaborate election process. An interesting rule is that the number of members younger than 70 cannot exceed 200 (Posfai is 49). Pósfai reports that a noteable consequence of being a member is that some people laugh significantly louder when you tell a joke than they used to.

Pósfai was a postdoctoral research associate at ASU from 1992 to 1994 and again from 1996 to 1998 in the 7*M research group of Professor Peter Buseck in the then Departments of Geology and Chemistry. Since leaving ASU he has been on the faculty and is currently professor in the Department of Earth and Environmental Sciences, University of Pannonia, a relatively new university in Hungary.

While at ASU, he started his dual areas of research acclaim: a) Characterization of individual species in atmospheric aerosol particles to understand their formation and transport and to learn about their role in atmospheric processes and in global climate change, and b) Biologically controlled mineralization in magnetotactic bacteria, and synthesis and characterization of the physical and chemical properties of nanoparticles of iron sulfides and iron oxides.

”It is great to be back at ASU. I arrived here for the first time exactly 20 years ago as a postdoc. The campus has impressively expanded since then but it still feels like home, with many familiar faces and a vibrant atmosphere,” says Pósfai. ”The first week was spent by settling in, getting a glimpse of the wonderful new electron microscopes, and starting on new projects in environmental mineralogy.”

During his month on campus, Pósfai will be working on both atmospheric chemistry problems, primarily on whether or not the structural variations in soot are related to its bulk properties such as toxicity. He will also be looking at biominerals; a new project is underway to better understand the role of algae in the precipitation of calcite from lakewater.

Pósfai and Buseck have had a continuing collaboration through the years. They most recently had a paper on ”Nature and climate effects of tropospheric aerosol particles” appear in the 2010 Annual Review of Earth and Planetary Sciences. In 1998 two of their papers were published in Science about electron microscopy of bacteria that contain magnetic nanocrystals. One of those was co-authored with ASU researchers R. Dunin-Borkowski and M. McCartney of the Department of Physics.

The election of Pósfai is an honor both to his home institution and to ASU, which helped foster the creativity of this celebrated and relatively young scientist.


(Nikki Cassis)


Biogeochemist’s research on Biological Soil Crusts shows link between geology and biology

Biological soil crusts (BSCs) are complex communities of organisms, including cyanobacteria (commonly known as blue-green algae), mosses, lichens, and fungi that occupy arid and semi-arid regions challenging to higher life forms. To the untrained eye, they resemble dry, dusty clumps of soil and moss, but BSCs are a vital link between sterile land and flourishing ecosystems. BSCs convert essential elements like nitrogen and carbon into bioavailable forms, they decrease water runoff, and increase water retention. In essence, they increase the habitability of their environments.

Katie Noonan, a SESE PhD student in biogeochemistry, studies BSCs in Moab, Utah. Noonan has been interested in the intersection between geology and biology since her undergraduate years at the University of California, Davis. “I have always been fascinated by the relationship between the fields [of geology and biology],” says Noonan, “And so I’ve always been interested in research that bridges the two. After beginning my graduate career at ASU I recognized that chemistry provides the direct link between geology and biology and so I decided I wanted a project that had aspects of all three fields.”

Noonan was attracted to ASU’s geology program because of its emphasis on interdisciplinary research. “The interdisciplinary attitude of my advisor and committee has made my research project possible,” she says. “My project has aspects of microbiology, ecology, geochemistry, biochemistry, soil science, and mineralogy. Noonan’s project is funded by a National Science Foundation Biogeosciences grant to SESE faculty members Hilairy Hartnett, an organic geochemist, and Ariel Anbar, a trace-metal geochemist. Ferran Garcia-Pichel, a geomicrobiologist, from the School of Life Sciences is also a collaborator on the project. Without the support of researchers across these fields I would not have been able to include such a diverse array of topics in my dissertation.”

Noonan’s thesis explores this chemical linking between geology and biology. BSC communities need a variety of metals to perform their biological functions, such as photosynthesis and nitrogen fixing, but these metals are often insoluble in the arid environments in which the crusts form. Somehow, the BSC organisms must be able to extract the metals from their environment; they could not otherwise survive.

Noonan hypothesized that BSC microbes produce small organic compounds called siderophores that bind metals in their environment, releasing them from minerals and making them available for microbial uptake. Siderophores therefore act as chemical weathering agents: they chemically break down rocks and minerals to their constituent elements, directly linking microbes in the BSCs to the minerals on which they rely.

To test her hypothesis, Noonan collected BSC samples from her field site near Moab. She used a biochemical assay to screen for siderophore-producing microbes, then isolated and cultured these organisms, and used gene sequencing to identify them. Her results were exciting: 70% of the organisms she screened turned out to produce siderophores, and she found five novel siderophores-producing organisms in her samples. Her results, combined with those of previous research, indicate that siderophores-producing organisms account for some of the dominant BSC microbes.

This is the first time siderophore production has been reported in BSCs, and it adds immeasurably to our understanding of how metals are cycled through arid ecosystems. The work also has much broader implications, from astrobiology to land conservation. “BSCs live in an extreme environment characterized by intense UV radiation, low water availability, and drastic fluctuations in temperature,” says Noonan. These conditions
are similar to those under which life on Earth evolved. “BSCs are adapted to withstand these conditions,” she continues, “so understanding how they evolved and how they function is important for understanding the development of terrestrial ecosystems on Earth and can also be applied to potential life on other planets.” This project was also funded in part by the ASU NASA Astrobiology Institute.

“BSCs are crucial members of their ecosystems because they provide the primary source of bioavailable carbon and nitrogen, increase soil stability and water retention, and influence the bioavailability of trace metals,” says Noonan. The soil crusts are
fragile, though, and are easily disturbed by livestock grazing or vehicle traffic. “When these activities destroy BSCs it takes them decades to recover,” says Noonan. “[That] causes the ecosystem to suffer and can lead to desertification.” Her study will help conservationists understand how to increase the growth in BSC communities, and decrease damage to them from anthropogenic activities.

In December, Noonan presented her research at the annual meeting of the American Geophysical Union (AGU) in San Francisco, CA. Along with approximately
20,000 professionals, students, professors, and policy makers, she attended other presentations, talked about her own work, and met with friends and colleagues. Noonan enjoys and values AGU as a venue to share her work.

“AGU is a very interdisciplinary venue with presentations on a variety of topics,” she says. “Because so many people attend the conference it is an excellent opportunity to reconnect with old colleagues and catch up on the work everyone is doing. There are always sessions that are directly related to my work, but also sessions that give me new ideas and fresh motivation.”

(Alice Letcher)


Caption: Katie Noonan holds a culture of a cyanobacterium she isolated from the crust, which is one of the nine organisms she isolated that produce
siderophores, small organic compounds that microbes make to increase iron bioavailability. Credit: Patrick Scott Noonan


On March 1, SEDS (Students for the Exploration and Development of Space) had the honor of being invited to a special luncheon sponsored by the Barrett Honors College and TEDx, featuring Astronaut Cady Coleman. After being introduced by Barbara Barrett (who has also been trained as an astronaut), she gave a very entertaining and informative talk, regarding life in space during her six-month mission to the International Space Station (ISS) during Expedition 27.

Focusing mainly on the scientific research performed on the ISS, Coleman gave an overview of the various types of research the astronauts do.  From fluid dynamics to combustion, there is quite a bit that goes on in the orbiting laboratory. She even cited some exciting research being done in collaboration with ASU’s very own Biodesign Institute.  The work being performed on the ISS provides great insight into aspects of nature that cannot be observed under the effects of gravity.  Flames behave differently, and perfect crystals can be grown in the microgravity environment. Coleman mentioned her favorite experiments to perform involved fluid dynamics, and when she performed certain tasks, such as adding air to the fluid, the fluid did not behave as the scientists back on Earth predicted.  There are many questions still waiting to be solved, thanks to our astronauts on the ISS.

Coleman also shared a fun video of her playing a flute duet with the legendary Ian Anderson of Jethro Tull, while she was in space and he was on Earth!  After her talk, she had a Q&A period, and the students attending had the opportunity to ask her their own questions of what it was like to live in space. She even stayed to meet each of us in person, when all our questions were answered.

This is actually second time SEDS has had the opportunity to meet Cady Coleman. We were invited to meet her at a similar luncheon two years ago, before her most recent trip to space.  Like last time, she was an overall wonderful person and always a pleasure to meet. We at SEDS would like to thank Dr. Coleman for visiting ASU once again and sharing with us her spectacular experiences. We wish her well on all her future endeavors!

Jim Crowell


Ten years ago, on February 19, 2002, the Thermal Emission Imaging System (THEMIS), a multi-band camera on NASA's Mars Odyssey orbiter, began scientific operations at the Red Planet. Since then the camera has circled Mars nearly 45,000 times and taken more than half a million images at infrared and visible wavelengths.

"THEMIS has proven itself a workhorse," says Philip Christensen, the camera's designer and principal investigator. Christensen is a Regents' Professor of geological sciences in the School of Earth and Space Exploration, part of Arizona State University's College of Liberal Arts and Sciences. "It's especially gratifying to me to see the range of discoveries that have been made using this instrument."

Highlights of science results by THEMIS over the past 10 years include:

* Confirming that hematite is widespread on Meridiani Planum, which led NASA to send one of its Mars Exploration Rovers there

* Discovering CO2 gas jets at the south polar ice cap in spring

* Discovering chloride salt deposits across the planet

* Making the best global image map of Mars ever done

* Identifying safe landing sites for NASA's Mars Phoenix spacecraft by finding the locations with the fewest hazardous boulders

* Monitoring dust activity in the Martian atmosphere

* Discovering that a large impact crater, Aram Chaos, once contained a lake

* Discovering that Mars has more water-carved channels than previously thought

* Discovering dacite on Mars, a more evolved form of volcanic lava not previously known on the Red Planet

THEMIS combines a 5-wavelength visual imaging system with a 9-wavelength infrared imaging system. By comparing daytime and nighttime infrared images of an given area, scientists can determine many of the physical properties of the rocks and soils on the ground.

Mars Odyssey has a two-hour orbit that is nearly "Sun-synchronous,"
meaning that Odyssey passes over the same part of Mars at roughly the same local time each day. In September 2008 its orbit was shifted toward an earlier time of day, which enhanced THEMIS' mineralogical detection capability.

Says Christensen, "Both Odyssey and THEMIS are in excellent health and we look forward to years more science with them."

NASA launched the Mars Odyssey spacecraft April 7, 2001, and it arrived at Mars October 24, 2001. On arrival the spacecraft spent several months in a technique called aerobraking, which involved dipping into the Martian atmosphere to adjust its orbit. In February 2002, science operations began.

The Mars Odyssey project is managed by the Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems in Denver built the spacecraft, and JPL and Lockheed Martin collaborate on operating it.

Caption 1: This was the first science image of Mars taken by THEMIS, February 19, 2002. It shows an area in Acheron Fossae, north of the giant volcano Olympus Mons, where mesas and valleys lie bounded by geologic faults. The image (V00816002) shows an area 11 x 6 miles (19 x 9 km); the smallest details visible in the original image are 59 feet (18 meters) wide. Photo by: NASA/JPL-Caltech/Cornell/Arizona State University

Caption 2: Taken on THEMIS' 10th anniversary, this image shows a region on Mars in Nepenthes Mensae, part of Terra Cimmeria. The view depicts a knobby landscape where the southern highlands are breaking up as the terrain descends into the northern lowlands. The image (V45173011) covers 11 x 32 miles (19 x 52 km); the smallest details visible in the original image are 59 feet (18 meters) wide. Photo by: NASA/JPL-Caltech/Cornell/Arizona State University


(Robert Burnham)



Sumner Starrfield, Regents’ Professor of Astrophysics in the School of Earth and Space Exploration at Arizona State University, is part of an international team that has, for the first time, discovered buckyballs in a solid form in space. Prior to this discovery, the microscopic carbon spheres had been found only in gas form in the cosmos.

Formally named buckminsterfullerene, buckyballs are named after their resemblance to the late architect Buckminster Fuller’s geodesic domes. They are made up of 60 carbon atoms arranged into a hollow sphere, like a soccer ball.

In the latest discovery, scientists used data from NASA’s Spitzer Space Telescope to detect tiny particles consisting of stacked buckyballs. They found the particles around a pair of stars called “XX Ophiuchi” that are 6,500 light-years from Earth, and detected enough to fill the equivalent in volume to 10,000 Mount Everests.

“These buckyballs are stacked together to form a solid, like oranges in a crate,” said Nye Evans of Keele University in England, lead author of a paper appearing in the Monthly Notices of the Royal Astronomical Society. “The particles we detected are minuscule, far smaller than the width of a hair, but each one would contain stacks of millions of buckyballs.”

Buckyballs were detected definitively in space for the first time by Spitzer in 2010. Spitzer later identified the molecules in a host of different cosmic environments. It even found them in staggering quantities, the equivalent in mass to 15 Earth moons, in a nearby galaxy called the Small Magellanic Cloud.

In all of those cases, the molecules were in the form of gas. The recent discovery of buckyballs particles means that large quantities of these molecules must be present in some stellar environments in order to link up and form solid particles. The research team was able to identify the solid form of buckyballs in the Spitzer data because they emit light in a unique way that differs from the gaseous form.

Starrfield, who has been using Spitzer to obtain infrared spectra of a number of recent stars, including XX Ophiuchi, was involved in writing the proposal to conduct the observations with Spitzer. He also was involved in analyzing and interpreting the data. The team chose XX Ophiuchi because it was already known to be a puzzling system of stars. Although the researchers did not expect to find buckyballs, they performed an extremely careful analysis of the light emitted by this stellar system and were on the alert for any unusual signals.

Starrfield has been using Spitzer because “its infrared detectors are superb for studying cold objects in the universe, much colder than our own Sun. We had known that buckyball molecules had been discovered around a few other stars but never expected to find them collected together in small particles.” According to Starrfield, “We have now identified features in the infrared that convince us that solid buckyball particles exist. Astronomers can now search for these same features in other stars that emit infrared light and hopefully find a lot of these particles.”

Buckyballs have been found on Earth in various forms. They form as a gas from burning candles and exist as solids in certain types of rock, such as the mineral shungite found in Russia, and fulgurite, a glassy rock from Colorado that forms when lightning strikes the ground. In a test tube, the solids take on the form of dark, brown “goo.”

“Buckyballs were studied by Sumio Ijima, a solid state physicist in Japan who was actually at ASU from 1970 to 1982,” says Starrfield. “So, we were pleased to continue his studies in space. They have been under continuous study for decades with possible uses in drug delivery and armor.”

“The window Spitzer provides into the infrared universe has revealed beautiful structure on a cosmic scale,” said Bill Danchi, Spitzer program scientist at NASA Headquarters in Washington. “In yet another surprise discovery from the mission, we’re lucky enough to see elegant structure at one of the smallest scales, teaching us about the internal architecture of existence.”


Caption: NASA’s Spitzer Space Telescope has detected the solid form of buckyballs in space for the first time. To form a solid particle, the buckyballs must stack together, as illustrated in this artist’s concept showing the very beginnings of the process. The buckyball particles were spotted around a small, hot star -- a member of a pair of stars, called XX Ophiuchi, located 6,500 light-years from Earth. Credit: NASA/JPL-Caltech


(Nikki Cassis)


New images acquired by NASA’s Lunar Reconnaissance Orbiter (LRO) spacecraft show that the Moon’s crust is pulling apart – at least in some small areas. High-resolution images obtained by the Lunar Reconnaissance Orbiter Camera (LROC) provide evidence that the Moon has experienced relatively recent geologic activity.

In new LROC images, a team of researchers discovered small, narrow trenches typically only hundreds to a few thousand meters (yards) long and tens to hundreds of meters wide, indicating the lunar crust is being pulled apart at these locations. These linear troughs or valleys, known as graben, are formed when crust is stretched, breaks and drops down along two bounding faults. A handful of these graben systems have been found across the lunar surface. The team proposes that the geologic activity that created the graben occurred less than 50 million years ago (very recent compared to the Moon’s current age of over 4.5 billion years).

In August, 2010, the team identified physical signs of contraction on the lunar surface, in the form of lobe-shaped ridges or scarps (known as lobate scarps), using LROC images. They suggest that these scarps indicate the Moon shrank globally in the geologically recent past and might still be shrinking today. The team saw these scarps widely distributed across the Moon and concluded that it was shrinking as the interior slowly cooled. The new images of graben therefore present a contradiction – regions of the lunar crust that are being pulled apart as the Moon shrinks. 

“We think the Moon is in a general state of global contraction due to cooling of a still hot interior. The graben tell us that forces acting to shrink the Moon were overcome in places by forces acting to pull it apart,” said Thomas Watters of the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum, lead author of a paper on this research appearing in the March issue of the journal Nature Geoscience. “This means the contractional forces shrinking the Moon cannot be large, or the small graben might never form.”

The small graben indicate that contractional forces in the lunar crust are relatively weak. The weak contraction indicates that unlike the terrestrial planets – Mercury, Venus, Earth, and Mars – the Moon did not completely melt in the very early stages of its evolution. Instead, an alternative scenario better fits the observations: only the Moon’s exterior initially melted forming a magma ocean.

“It was a big surprise when I spotted graben in the farside highlands!” said Mark Robinson of the School of Earth and Space Exploration at Arizona State University, coauthor and principal investigator of LROC. “I immediately targeted the area for high resolution stereo images so we could create a 3-dimensional view of the graben. It’s exciting when you discover something total unexpected. Only about half the lunar surface has been imaged in high resolution. There is much more of the Moon to be explored.”

As the LRO mission progresses and coverage increases, scientists will have a better picture of how common are these young graben, and more importantly what other types of tectonic features are nearby. The number of graben systems the team finds may help scientists refine the state of stress in the lunar crust.

(Nikki Cassis)

Photo 1: Newly detected series of narrow linear troughs are known as graben, and they formed in highland materials on the lunar farside. Forces acting to pull the lunar crust apart formed the Virtanen graben, informally named for a nearby impact crater. These graben are located on a topographic rise with several hundred meters of relief revealed in topography derived from Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) stereo images (blues are lower elevations and reds are higher elevations). The rise is flanked by the rim of a ~2.5 km diameter degraded crater. Credit: NASA/GSFC/Arizona State University/Smithsonian Institution

Photo 2: A series of graben in a patch of mare basalts that occupy a valley south of Mare Humorum cut across and deformed several small diameter impact craters. The walls and floors of the graben crosscut a degraded 27 m diameter crater (inset, upper white arrow) and a 7 m diameter crater (inset, lower white arrow). Since small craters only have a limited lifetime before they are destroyed by other impacts, their deformation by graben indicates that these fault-bound troughs are relatively young. Credit: NASA/GSFC/Arizona State University/Smithsonian Institution


In an article titled, "Russian hot springs point to rocky origins for life," New Scientist writer Colin Barras tackles the question that strikes at the very heart of one of the deepest mysteries in the universe: how did life begin on Earth? New findings challenge the widespread view that it all kicked off in the oceans, around deep-sea hydrothermal vents. Life may have begun on land instead – just as Darwin thought

Although conventional wisdom has it that hydrothermal vents on the ocean floor offered an ideal chemical environment for the earliest life, Paul Knauth, a geologist in ASU's School of Earth and Space Exploration, thinks life may not have begun in the sea. "The early ocean was a deathtrap of hot salty water," he says. "I like the idea of a non-marine origin."

Knauth has analyzed the oxygen isotopes in the silica-rich rocks deposited early in Earth's history, from which you can work out temperatures at the time the rocks formed. He says that the entire planet was much hotter than anyone suspected – surface temperatures of 50 to 80 0C may have been common. The seas were also twice as salty as today, because so-called "evaporitic" deposits - which locked away vast quantities of salt - had not begun to form.

Read the full article here


In many ways, soil is fundamental to life. Flora and fauna depend on its presence for their survival as much as they depend on water and air. In order to sustain its soil content, an ecosystem needs to maintain a balance between rates of soil erosion and soil production. Factors such as tectonic plate movement or climate change can tip this balance, and learning how such changes affect soil cover is crucial to our understanding of how the Earth’s surface works.

In a series of studies appearing in the journals Nature Geoscience, Earth Surface Processes and Landforms, and Earth and Planetary Science Letters, researchers at Arizona State University are providing new insights into how soil production processes respond to erosion in mountainous regions.

The studies utilized an ideal natural laboratory in the San Gabriel Mountains, a region in southern California, where previous work quantified a large range of erosion rates.

In the study released Feb. 5 in Nature Geoscience, Arjun Heimsath, associate professor in the School of Earth and Space Exploration (SESE) in ASU’s College of Liberal Arts and Sciences, and co-authors measured soil production rates across the large gradient in erosion rates. Previous models suggested that once soil production rates reach a certain rate, they remain constant even if background erosion rates continue increasing. After making their measurements, the team recorded soil production rates that far exceeded this model’s upper limit of soil production; contrary to previously held popular belief, the team found that soil production rates can keep up with very rapid erosion rates.

“One reason why this data is so exciting is because the previous way that we and other people viewed the world — the previous conceptual framework — was that there was an upper limit of soil production,” said Heimsath. “There was thought to be a maximum possible rate of soil production and anything above that was not possible. We’ve found that the landscape is responding to this higher erosion rate by producing soil more rapidly, and that makes us rethink the way that we have believed the Earth’s surface is responding to changes.”

In a second study, in press in Earth Surface Processes and Landforms, led by Roman DiBiase, a recent doctoral student of SESE professors Whipple and Heimsath, the team developed a new method for determining where bedrock emerges in a landscape. Stitching together a series of high-resolution photographs and magnifying the composite image to compare with high-resolution topographic data and field observations, the researchers developed a method to accurately predict rock exposure from remotely sensed data. They used this technique to examine the details of the landscape’s progression from soil to exposed rock in DiBiase’s study, and also applied the technique for use in Heimsath’s paper.

A third study, soon to appear in Earth and Planetary Science Letters, examined the relationship between chemical weathering — how rainfall chemically erodes a landscape — and erosion rates. The study’s lead author, Jean Dixon, previously a postdoctoral researcher with Heimsath, found that chemical weathering rates increased along with soil erosion rates up to a certain maximum limit, after which point chemical weathering rates decreased even as soil erosion rates continued to rise. This phenomenon was predicted in a previous model, but this study marks the first time field-based data and observations verified the model.

“Because of doing the studies in the exact same place, we now have the ability to know how soil production is related to chemical weathering,” said Heimsath. “And that’s the next step, to really put them together even more clearly.”

One interesting question the research raises is whether soil production rates do not have an upper limit, or whether the upper limit is just far higher than previously thought.

The team is also interested in pinpointing the mechanisms that explain their observations—how the landscape manages to keep up its rate of soil production with such rapid erosion rates. One hypothesis is that the biology of the landscape—the flora and fauna that are responsible for and dependent on much of the soil produced in mountainous regions—are working harder to maintain soil production rates to keep pace with erosion. Heimsath said that finding the answers to these questions will be the researchers’ next endeavor.

“The presence of soil sustains our ecosystems,” said Heimsath. “It sustains vegetation, and all the life that exists in mountainous regions. Understanding what sets the upper limit of soil cover is really important to understanding what can sustain life in some of these landscapes.”

The research was funded by the National Science Foundation with a grant to Whipple and Heimsath.

A team comprised of Roman DiBiase (left), a recent SESE doctoral student of SESE, and professors Arjun Heimsath (middle) and Kelin Whipple (right), conducted research in the San Gabriel Mountains, a region in southern California. Their research provides new insights into how soil production processes respond to erosion.


(Victoria Miluch)