Nikki Staab

Unearthing earthquake enigmas

dianeb — Thu, 21 Jan 2010 13:27:13 -0700

by Nikki Staab

Researchers at Arizona State University and University of California-Irvine are revealing new information about fault behavior and ultimately affecting how we understand the potential for damaging earthquakes.

The researchers' findings of stream channel offsets along the San Andreas Fault encompasses their work at the Carrizo Plain, which is located 100 miles north of Los Angeles and site of the original “Big One”—the Fort Tejon quake of 1857. Applying a system science approach, the ASU-UCI team presents a pair of studies appearing Jan. 21 in Science Express that incorporates the most comprehensive analysis of this part of the San Andreas fault system to date.

In one of the studies, Ramon Arrowsmith, associate professor in the School of Earth and Space Exploration in ASU’s College of Liberal Arts and Sciences, and Olaf Zielke employed topographic measurements from LiDAR (Light Detection and Ranging), which provide a view of the earth’s surface at a resolution at least 10 times higher than previously available, enabling the scientists to “see” and measure fault movement, or offset.

To study older earthquakes, researchers turn to offset landforms such as stream channels which cross the fault at a high angle. A once straight stream channel will have a sharp jog right along the fault and indicate that prior offset.

This highly detailed overhead view of Carrizo Plain stream channels measured the offset features linked to large earthquakes in this section of the southern San Andreas Fault.

“This virtual approach is not a substitute for going out and looking at the features on the ground,” said Zielke, who earned his doctorate at ASU under Arrowsmith. “But it is a powerful and somewhat objective approach that is also repeatable by other scientists.”

In the second Science Express study, a team led by UCI’s Lisa Grant Ludwig with postdoctoral scholar Sinan Akciz and doctoral candidate Gabriela Noriega, determined the age of offset in a few Carrizo Plain dry stream channels by studying how much the fault slipped during previous earthquakes. The distance that a fault "slips"—or moves—determines its offset.

View of the “Southeast” channel of the Bidart fan, Carrizo Plain, looking downstream. Credit: Bidart Fan San Andreas fault research team, University of California Irvine and Arizona State University

By digging trenches across the fault, radiocarbon-dating sediment samples and studying historic and older weather data of these Carrizo Plain channels, and combining them with the LiDAR data, the researchers found something other than what scientists had thought. Instead of having the same slip repeat in characteristic ways, researchers found that slip varied from earthquake to earthquake.

“When we combine our offset measurements with estimates of the ages of the offset features determined by Lisa’s team and the ages of prior earthquakes, we find that the earthquake offset from event to event in the Carrizo Plain is not constant, as is current thinking,” Arrowsmith said.

“The idea of slips repeating in characteristic ways along the San Andreas Fault is very appealing, because if you can figure that out, you are on your way to forecasting earthquakes with some reasonable confidence,” added Ludwig, associate professor of public health. “But our results show that we don’t understand the San Andreas Fault as well as we thought we did, and therefore we don’t know the chances of earthquakes as well as we thought we knew them.”

Before these studies, the 7.8 magnitude Fort Tejon earthquake of 1857 (the most recent earthquake along the southern San Andreas Fault) was thought to have caused a 9 meter to 10 meter slip along the Carrizo Plain. But the data the teams acquired show that it was actually half as much, and that slip in some of the prior earthquakes may have been even less. The researchers also found that none of the past five large earthquakes in the Carrizo Plain, dating back 500 years, produced slip anywhere near 9 meters. In fact, the maximum slip seen was about 5 meters to 6 meters, which includes the slip caused by the Fort Tejon quake.

This result changes how we think the San Andreas Fault behaves—it probably is not as segmented in its release of accumulated stress. This makes forecasting future earthquakes a bit harder because we cannot rely on the assumption of constant behavior for each section. It could mean that earthquakes are more common along the San Andreas, but some of those events are probably smaller than we had previously expected.

Since the 1857 quake, an approximate 5 meters of strain, or potential slip, has been building up on the San Andreas Fault in the Carrizo Plain, ready to be released in a future earthquake. In the last five earthquakes, the most slip that has been released was 5 meters to 6 meters in the big 1857 quake. This finding points to the potential of a large temblor along the southern San Andreas Fault.

“Our collaboration has produced important information about how the San Andreas Fault works," Arrowsmith said. "Like all science, it is pushed forward by hard work, good ideas and new technology. I am optimistic that these results, which change how we think about how faults work, are moving us to a more subtle understanding of the complexity of the earthquake process.”

“The recent earthquake in Haiti is a reminder that a destructive earthquake can strike without warning," Ludwig said. "One thing that hasn’t changed is the importance of preparedness and earthquake resistant infrastructure in seismically active areas around the globe.”

Both studies were supported by the National Science Foundation, U.S. Geological Survey, and Southern California Earthquake Center.

MESSENGER team releases first global map of Mercury

dianeb — Thu, 17 Dec 2009 16:45:03 -0700

by Nikki Staab

NASA's MESSENGER mission team and cartographic experts from the U. S. Geological Survey have created a critical tool for planning the first orbital observations of the planet Mercury—a global mosaic of the planet that will help scientists pinpoint craters, faults and other features for observation. The map was created from images taken during the MESSENGER spacecraft's three flybys of the planet and those of Mariner 10 in the 1970s. A presentation on the new global mosaic is being given today at the fall meeting of the American Geophysical Union in San Francisco.

Global map of Mercury showing regions imaged by MESSENGER during three flybys. Each image block is a mosaic of multiple spacecraft images. Black areas indicate no coverage.

The MESSENGER spacecraft completed its third and final flyby of Mercury on Sept. 29, concluding its reconnaissance of the innermost planet. The MESSENGER team has been busily preparing for the yearlong orbital phase of the mission, beginning in March 2011, and the near-global mosaic of Mercury from MESSENGER and Mariner 10 images is key to those plans.

"The production of this global mosaic represents a major milestone for everyone on the MESSENGER imaging team," said MESSENGER principal investigator Sean Solomon of the Carnegie Institution of Washington. "Beyond its extremely important use as a planning tool, this global map signifies that MESSENGER is no longer a flyby mission but instead will soon become an in-depth, nonstop global observatory of the Solar System's innermost planet."

"The process of making a mosaic may seem relatively straightforward—simple software can stitch together panoramas from multiple images. However, the challenging part has been to make cartographically accurate maps from a series of images with varying resolution (from about 100 to 900 meters per pixel) and lighting conditions (from noontime high sun to dawn and dusk) taken from a spacecraft traveling at speeds greater than 2 kilometers per second (2,237 miles per hour)," said Mark Robinson, a professor in Arizona State University's School of Earth and Space Exploration in the College of Liberal Arts and Sciences. Robinson is a member of the MESSENGER Science Team.

Small uncertainties in camera pointing and changes in image scale can introduce small errors between frames, Robinson said. "And with lots of images, small errors add up and lead to large mismatches between features in the final mosaic. By picking control points—the same features in two or more images—the camera pointing can be adjusted until the image boundaries match." This operation is known as a bundle-block adjustment and requires highly specialized software.

Cartographic experts at the USGS Astrogeology Science Center in Flagstaff, Ariz., picked the control points to solve the bundle-block adjustment to construct the final mosaic using the Integrated Software for Imagers and Spectrometers (ISIS). For the MESSENGER mosaic, 5,301 control points were selected, and each control point on average was found in more than three images (18,834 measurements) from a total of 917 images. Scientists at ASU and the Johns Hopkins University Applied Physics Laboratory (APL) were also instrumental in making the mosaic possible.

"This mosaic represents the best geodetic map of Mercury's surface," said Kris Becker of the USGS. "We want to provide the most accurate map for planning imaging sequences once MESSENGER achieves orbit around Mercury.

"As the systematic mapping of Mercury's surface progresses, we will continually add new images to the control point network, thus refining the map. It has already provided us with a start in the process of naming newly identified features on the surface."

In the final bundle-block adjustment the average error was about two-tenths of a pixel or only about 100 meters—which is an excellent match from image-to-image. The biggest remaining issue is the absolute control of features on the surface. For instance, if the North Pole is not precisely at the spin axis you could have a mosaic in which all the seams overlapped perfectly, but the whole mosaic could slide around like the skin of an orange that somehow became detached from the interior fruit.

Much work was done with the Mariner 10 images collected in 1974 and 1975 to make an absolute control network even though only 45 percent of the planet was seen at the time. The longitude system for Mercury is tied to a small crater named Hun Kal (the number twenty in an ancient Mayan language, because the crater is centered at 20°W). For now, MESSENGER data are tied to the earlier Mariner 10 control network.

Absolute positional errors in the new mosaic are about two kilometers, according to the MESSENGER team. Once the MESSENGER spacecraft orbits Mercury, much progress will be made refining the relative and absolute control of the MESSENGER (and Mariner 10) images, and the entire planet will be imaged at even higher resolution. The global mosaic is available for download on the USGS Map-a-Planet Web site, http://www.mapaplanet.org.

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus and Mercury, will start a yearlong study of its target planet in March 2011.

NASA gets a new set of moon wheels

dianeb — Mon, 21 Sep 2009 15:29:39 -0600

by Nikki Staab

NASA’s Desert RATS are always testing new technology. Every year, they spend two weeks in the Arizona desert at Black Point Lava Flow to do tests in anticipation of future lunar exploration. The RATS are members of the Desert Research and Technology Studies group. The group includes engineers and geologists from several NASA laboratories. This year’s tests included several private and academic partners, including two key members from ASU's School of Earth and Space Exploration.

Team members got a tough workout as part of the recent tests. Two crew members, an astronaut and a geologist, lived for more than 300 hours inside NASA's new lunar wheels, the Lunar Electric Rover (LER). The explorers scouted the area for features of geological interest. They then donned spacesuits and conducted simulated moonwalks to collect samples. The crew also docked to a simulated habitat, drove the rover across difficult terrain, performed a rescue mission, and made a four-day traverse across the rough landscape.

“We are continuously working to meet the challenges of a human outpost on the moon,” says James Rice, faculty research associate in the school and principal investigator of one of the study's geology traverses. “To meet these challenges, scientists and engineers must conduct hands-on field tests and research here on Earth. That prepares us to better understand the complex challenges that will be encountered on the moon.”

Everything gets tested again and again. Researchers test the robotics, vehicles, and habitats. The key is to study them in realistic environments. This helps astronauts, engineers and scientists to define better ways to combine human and robotic efforts that will enhance scientific exploration. The Arizona desert is well suited for testing technologies and procedures for future human-robotic exploration in extreme environments.

“You have to test hardware and concepts in a real-world environment with real geology, slopes, rocks, dust...and the unexpected,” Rice says. “It can't be done in a controlled laboratory. The terrain of Black Point Lava Flow contains challenging topography for LER operations. It also contains lunar and Mars analog geomorphology and geology.”

Rice was in charge of making traverse routes or paths that the rover and crew followed during the simulation. He had to factor in science objectives, rover driving speed, time for the crew to put on and take off spacesuits before and after geology investigations, and the time required to drive to the next station.

“We had a very detailed timeline from Mission Control that we had to work with to make sure we achieved our science goals,” says Rice, who has been involved with the field tests for about six years. “Sometimes we had issues with loss of communications, equipment, or the rover. This caused the whole operation to get behind on the timeline. It was very realistic.”

Kip Hodges is the founding director of the school in ASU's College of Liberal Arts and Sciences and science team member of Desert RATS. He was the principal scientist of the K10 robot, which was developed at NASA's Ames Research Center and deployed prior to the simulated mission to identify areas of interest for the crew. He also served in the science “backroom” for the LER human tests.

“The K10 robot was employed in these tests in order to evaluate the added value of robotic reconnaissance of a planetary landscape prior to sending humans into the field for scientific research,” says Hodges. “While the final field test results are not yet in, I think that my collaborators and I are extremely pleased with the exercise. We look forward to further tests. For example, we are also using K10 for follow-up work after human exploration. In that case, our analogue study site is in a bit farther afield: the high Arctic of Canada. Perhaps we'll also deploy K10 for this purpose next year at the Desert RATS tests.”

New wheels for a new generation of exploration
LER is the next-generation moon rover. It is an all-electric vehicle with 12 wheels. A little bigger than a Humvee, the LER was built for extreme exploration. The frame of this mobile base camp was developed in conjunction with an off-road race truck team, making it able to travel hundreds of kilometers over rugged terrain.

LER’s wheels can move sideways in a “crabbing” motion, one of many features that make it skilled at scrambling over rocks. During the mission, LER was able to climb slopes on the lava flow that the team's SUV chase vehicles couldn't handle. Remarkably, the advanced suspension and drive train of the LER allows it to perform such feats using only 20 horsepower. That is an order of magnitude less than the standard off-road vehicles it left in the dust.

If that isn't enough to make the Apollo-era astronauts envious, LER is also capable of housing two astronauts for up to two weeks with sleeping and sanitary facilities. It is equipped with a time- and space-saving concept called suit ports. The ports are designed to allow astronauts to quickly enter and exit their EVA suits via a rear-entry hatch.

“Apollo astronauts had to drive their lunar rover wearing space suits,” says Rice. “This new manned lunar rover concept has a pressurized environment. That will allow the crew to drive wearing more comfortable clothing and not be stuck in a space suit.”

NASA has not yet confirmed the technologies that will be used in future lunar missions. However, the successful testing of analogue systems and procedures in simulated environments here on Earth moves us one step closer to a sustainable human presence on the moon.

The Desert RATS tests have been held for more than a decade. Engineers from NASA centers work with representatives from industry and academia to determine what will be needed for human exploration of the moon and other destinations in the solar system. It is the culmination of the various individual science and advanced engineering discipline areas' year-long efforts. This year's work built on the investigations of previous years and increased the scope and length of the tests.

For media inquiries, contact Nikki Staab, School of Earth and Space Exploration, 602.710.7169, nstaab@asu.edu

Deep biosphere research points to new methods for recovering petroleum

ovprea — Thu, 23 Oct 2008 11:45:23 -0600

by Nikki Staab

Miles below us, deep within Earth's crust, life is astir—not with large creatures, but with microbes, the smallest and oldest form of life on Earth. These deep biosphere microorganisms are more diverse than life on the surface. Yet much about them is still unknown, including the origin of the organic compounds they consume. Arizona State University researchers are using a novel approach that integrates physical organic chemistry with organic geochemistry and biogeochemistry to uncover the source of these organic compounds.

Carbon, the building block of organic matter, is one of the most dynamic elements on the planet; it responds to biological, physical and chemical processes in many ways and on many timescales. Understanding how carbon is formed, where it comes from, and how much of it exists is important for a more detailed and coherent picture of the global carbon cycle. Yet a complete understanding of how carbon is produced and consumed in the environment still evades researchers. This is because much of what is known is based on processes that act on short time-scales and at Earth's surface.

Deep biosphere microbes, like any living organism, require energy to survive. For many, their sustenance comes in the form of organic compounds. Over time, organic compounds are buried and pushed deeper into the Earth's crust. Harsh conditions on the journey to the deep Earth cause the organic compounds to become "recalcitrant," meaning they are no longer in a form that microbes can use. Some of the consumable organic compounds are produced by other subsurface microbes, but a large portion is most likely the end product of a mysterious geochemical process.

Theoretical biogeochemist Everett Shock leads a group of researchers who are investigating how this geochemical transformation from recalcitrant matter to usable organic compounds occurs deep in Earth's crust.

"The secret appears to lie in how temperature and pressure affect the reactivity of organic compounds, and, maybe more importantly, how the properties of water change deep in sediments and sedimentary rocks," says Shock. "The transformation in how water behaves is so enormous that we would hardly recognize it as the same stuff that comes out of our kitchen taps."

Most organic reactions at the Earth's surface do not work very well in water. Either they need an organism that has evolved the mechanisms to promote organic reactions in water or they need an organic solvent, such as hexane or benzene. The very deep Earth, below where microbial life has been shown to exist, has lots of rocks but no organic solvents. It does, however, have very hot water.

The team hypothesizes that conditions deep in the Earth might be good for complex organic reactions.

"Evidence suggests that hot water at high pressures—conditions we'd find in the subsurface—is actually a very good solvent for organic reactions," says Hilairy Hartnett, a member of Shock's interdisciplinary team. "It might be possible for these reactions to occur without biology if the conditions are right."

She explains, "Biological processes can promote reactions to generate complex organic molecules even at unfavorable low temperatures and pressures—the difference for the deep Earth is the high temperature and pressure."

The team will apply new theoretical models of how water at high temperatures and pressures can transform organic compounds in unexpected ways. Through a series of high-temperature/pressure experiments involving organic compounds, water, and common minerals found in sedimentary rocks such as iron oxides and clays, the team plans to reveal how organic transformation reactions occur in natural geologic conditions.

John Holloway, emeritus professor of chemistry, designed and built the hydrothermal reaction vessels necessary for testing. At ASU's new Omni-pressure Lab, simple compounds such as water and carbon dioxide are placed in the inert gold capsules and then tested.

"The samples are held at temperatures up to 300 degrees Celsius and pressures of 250 atmospheres, equivalent to the bottom of the ocean (2,500 meters) or slightly higher, for periods of hours to weeks," explains Holloway. "They are then quenched to ambient conditions and we analyze the products using gas chromatography and mass-spectrometry."

The results of past similar experiments have shown that the concentration, variety, and complexity of compounds all increase with time, and are strongly influenced by contact with minerals during the experiments.

"It will be important to find out if the mixture of compounds we make in the lab looks anything like the organic compounds that are found in the deep subsurface," says Hartnett. "If they do, then maybe this is how they formed—just rocks, hot water and simple carbon compounds. If they don't, well, we need to figure out what else is required."

"Lots of researchers have looked at individual aspects of the questions we're asking, but this is one of the first—or maybe the first—attempt to look at these high-temperature water-rock-organic processes from an integrated experimental and theoretical standpoint," Hartnett says.

A project of this caliber requires a team with a wide range of expertise from thermodynamic modeling, reaction mechanisms, and organic characterization, to clay minerals and high-temperature/pressure experiments. Many different techniques and backgrounds are necessary to understand the complexities of the process.

"Some of the known organic reactions under hydrothermal conditions are fascinating to me as an organic chemist. But this is a not a research field that I can enter in my own, I don't know how to do the experiments and I don't know which are the important observations," says chemistry professor Ian Gould. "But I can bring expertise in the area of choosing useful and informative reactions to study."

"No one person is an expert in all aspects of the project. As a team, we all think about the same questions, but we each bring a different set of skills and ideas to the forum. That often means we can find answers more quickly, or find answers that come from a direction any one of us by ourselves might have overlooked," says Hartnett.

"What we're learning may be applied to hydrocarbon exploration, carbon dioxide sequestration, environmental reclamation, and microbial sustainability," says team member Lynda Williams, who focuses on the chemical composition of clay and sedimentary minerals. "It could also lead toward understanding primordial conditions on Earth and similar planets where carbon-based life has evolved," she adds.

This interdisciplinary approach to exploring organic reactions in hot water may also have important implications for "green" chemistry. By learning more about how to promote organic reactions in hot water, other researchers may be able to take that knowledge and develop new chemical processes that don't have to use environmentally unfriendly, toxic solvents.

Shock and his team will be the first to link organic geochemical reactions deep in the Earth's crust to the support of microbes in the deep biosphere. In the process, the researchers plan to test new ideas about how petroleum forms from deeply buried organic matter, including the direct involvement of deep biosphere microbes. That deeply buried organic material is the precursor to petroleum, but it may also be the food that many microbes need to survive.

"By understanding organic synthesis reactions in the deep biosphere, we may find better organic and inorganic tracers to aid in finding petroleum resources and recovering them in more environmentally friendly ways," says Williams.

This research is funded by the National Science Foundation's Emerging Topics in Biogeochemical Cycles program. For more information, contact Everett Shock, School of Earth and Space Exploration, Department of Chemistry and Biochemistry, College of Liberal Arts and Sciences, 480.965.0631. Send email to eshock@asu.edu

Solar system swap: Uranus and Neptune switched places

ovprea — Thu, 24 Jan 2008 12:17:37 -0700

by Nikki Staab

Quick: What's the order of the planets in the solar system? Need a little help? Maybe the following mnemonic rings a bell: "My Very Educated Mother Just Served Up Nine Pizzas." It's useful for remembering the order of the planets today, but it wouldn't have been as useful in the past, and not just because the International Astronomical Union demoted Pluto to "dwarf planet" last year.

The reason this mnemonic wouldn't have worked is because the planets weren't always in the order they are today. Four billion years ago, early in the solar system's evolution, Uranus and Neptune switched places.

This is the result of recent work by Steve Desch, an assistant professor in ASU's School of Earth and Space Exploration. The work appears in a recent issue of Astrophysical Journal. Desch based his conclusion on his calculations of the surface density of the solar nebula, which is the disk of gas and dust out of which all of the planets formed. The surface density—or mass per area—of the solar nebula protoplanetary disk is a fundamental quantity needed to calculate everything from how fast planets grow to the types of chemicals they are likely to contain.

It's very hard to observe the surface density in protoplanetary disks forming solar systems today, both because they're too far away and because most observations detect only dust and miss everything larger than a baseball. So, for the last 30 years, most researchers have relied on an estimate of the surface density: the Minimum Mass Solar Nebula.

The idea is simple: take the rocky component of each planet, add hydrogen and helium until it matches the Sun in composition, and spread the mass over the area of each planet's orbit. The minimum mass solar nebula predicts disk masses not too different from what we can observe in forming solar systems. But it also predicts low surface densities, with the mass too spread out to form planets quickly.

"I was thinking about planet formation and noticing that all the current models failed to predict how Jupiter could grow to its current size in the lifetime of the solar nebula," Desch says. "Given Jupiter's composition and size, models predicted it would take many millions of years for it to form, and billions of years for Uranus and Neptune—but our solar system isn't that old. That's when I ran across the Nice model."

The Nice model (named for the city in France where it was developed) is based on sophisticated numerical calculations of the planets' orbits over millions of years. It explains several aspects about the orbits of Jupiter, Saturn, Uranus and Neptune, as well as the Kuiper Belt of comets beyond, by assuming the giant planets formed a lot closer together than they're found today.

Neptune, for example, formed less than half the distance from the Sun that it orbits today. And in 50 percent of their simulations, Uranus and Neptune switched places, although there was no way to determine whether they did or not.

Desch realized the Nice model implied the mass of the solar system was packed together more tightly than the minimum mass solar nebula assumed. By spreading the masses of the planets over their original orbits, as predicted by the Nice model, he found a very smooth variation of surface density with distance from the Sun, albeit one that fell off very sharply far from the Sun. The fit varied by only a few percent from the planets' masses, but only if Uranus and Neptune did indeed switch places.

"Neptune had to form closer to the sun than Uranus, or you don't get the smooth profile," he says.

The new findings have other profound implications, too.

"The surface density of the solar nebula isn't what we originally thought—it is actually much higher—and this has implications for where we formed and for how fast planets grow," Desch says. "A higher surface density of the solar nebula means that Uranus and Neptune formed closer and faster, in only 10 million years instead of billions."

That's important because Uranus and Neptune contain a few Earth masses of hydrogen and helium gas, and observations of other protoplanetary disks show these gases don't hang around for more than 10 million years.

In addition to demonstrating for the first time that all of the giant planets can grow within the lifetime of the solar nebula, Desch also uncovered the reason behind the sharp variation in density with distance from the sun.

"The distribution of mass falls off very steeply because the outer edge is constantly being boiled away through the process of photoevaporation, by the ultraviolet radiation of nearby massive stars," he says.

Before this, researchers had not considered the effects of photoevaporation on the mass distribution of the solar system. Desch's work shows that photoevaporation does move mass from the outer edge—but at a fixed rate, so it keeps it from spreading out too much, thus aiding planet growth.

So it seems that 4 billion years ago, "My Very Educated Mother Just Served Nine Up Pizzas" would have been the mnemonic to learn.

"This reminds us that the solar system is a dynamic place," Desch says. "For the first 650 million years of the solar system, Neptune was closer to the sun than Uranus—that's 15 percent of the history of the solar system. It looked completely different than we see it today."

This article first appeared on the ASU News site. For more information contact Nikki Staab, School of Earth and Space Exploration, 480.965.8122, nstaab@asu.edu