Martian Clay Minerals Might Have Much Hotter Origin

Ancient Mars, like Earth today, was a diverse planet shaped by many different geologic processes. So when scientists, using rovers or orbiting spacecraft, detect a particular mineral there, they must often consider several possible ways it could have been made.

Several such hypotheses have been proposed for the formation of clay minerals, which have been detected from orbit and are sometimes considered indicators that the surface has, in the past, been altered by liquid water. Now, publishing in the journal Nature Geoscience, a team of French and American scientists led by Alain Meunier of the Université de Poitiers and including Caltech's Bethany Ehlmann, has suggested a new, very different possibility.

Previously, planetary scientists considered two hypotheses—both offering the potential for once-habitable environments on Mars—that explain clay mineral formation. One holds that over long enough periods, contact with liquid water can alter igneous rock, such as basalt, producing clays; the other proposes that waters flowing through the martian subsurface can produce clays through a hydrothermal process.

In the new paper, the authors suggest that the clay minerals instead might have precipitated directly from scalding hot magmas.

"This new hypothesis is less exciting for astrobiology because life could not survive in those types of conditions," says Ehlmann, an assistant professor of planetary science at Caltech and a research scientist at the Jet Propulsion Laboratory. "But all three hypotheses need to be on the table as we consider a given clay-bearing deposit. Each hypothesis has a different implication for the history and habitability of ancient Mars."

Ehlmann says that scientists hope to use the Curiosity rover and its suite of instruments to study the clays found in sediments at Gale Crater—the impact crater that the robotic geologist was sent to explore. However, she notes, clays are typically found in even older igneous bedrock on Mars. Future rover missions would need to study clay formation in that ancient crust to rigorously test the various clay formation hypotheses. "There's more exploration that needs to be done before we understand all the mysteries of Mars," she says.

The Los Angeles Times recently spoke to Ehlmann about the new paper and its implications.

Writer: 
Kimm Fesenmaier
Frontpage Title: 
Hotter Origin Possible for Martian Clays
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

Geologists in the Field

Field geologists at Caltech come face to face with bears and wolverines, climb steep cliffs and mountains, and endure scorching sunlight and frigid temperatures. Sometimes risking life and limb, they travel to some of the most remote corners of the globe—all in the name of science. A feature-length story in the Summer 2012 issue of E&S magazine describes some of their adventures in the quest to understand our planet. 

Writer: 
Marcus Woo
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

Anchors Aweigh

At Caltech, hydrophilic researchers in the Division of Geological and Planetary Sciences take to the salty seas to gather data, explore the deep, and get a firsthand view of the beasts at the bottom. The briny treasures they collect along the way are helping them learn more about past, present, and future environmental conditions and hazards. Read about their ocean adventures in a feature-length story in the Summer 2012 issue of E&S magazine.

Writer: 
Katie Neith
Frontpage Title: 
Ocean-based Researchers Take to the Sea
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

Countdown to Mars: Caltech goes to the Red Planet

On Sunday, August 5, the Mars Science Laboratory (MSL) rover, known as Curiosity, will make its dramatic descent onto Mars's surface. Once it lands, the rover will check its instruments to make sure everything's functioning properly—and then it will get right to work.

In fact, on just the second day of its Martian excursion, Curiosity is scheduled to turn on some of its key scientific instruments, taking pictures and making measurements of its immediate environment. About a week later, the rover will spin its six wheels and start exploring. Curiosity will ramp up its science mission over the following weeks, deploying its suite of instruments to scoop, drill, zap, examine, and analyze. And through it all, a couple of Caltech researchers will be among the 300 scientists working here on Earth, taking the information Curiosity sends home and trying to figure out what it all means.

Back in February, Caltech's Ken Farley and Bethany Ehlmann were named as participating scientists on the mission; each will be directing their own Martian science projects. Ehlmann, an assistant professor of planetary science and a JPL research scientist, has been analyzing rocks and minerals on Earth to help MSL's science team choose which Martian rocks to study in detail. Farley, the W. M. Keck Foundation Professor of Geochemistry and chair of the Division of Geological and Planetary Sciences, will measure the presence of noble gases in Martian rocks to determine their ages. Here are some excerpts from Kimm Fesenmaier's story about how these two scientists intend to make their mark on Mars.

Examining the capabilities of one of Curiosity's science instruments, Sample Analysis at Mars (SAM), which was designed to look for organic matter, Farley realized that it might be possible to detect the isotope helium-3 with SAM's spectrometer. Since helium-3 is produced by the bombardment of surface materials by incoming cosmic rays, measurements of the isotope can be used to determine how long rocks or other geologic features have been exposed on the surface of a planet. This could help scientists date features on Mars such as impact craters, but it could also come in handy in terms of target selection.

Imagine, for example, that the science team locates an impact site on Mars that seems to have been created within the last few million years. The rocks around that site would be ideal targets for closer study because any organic matter they contain would have been protected from cosmic rays until they were thrown out onto the surface. "The trouble is, it's easy to say that an impact happened a million years ago, but how would you ever really know?" Farley says. "The technique that I have is a way to say, 'Yes, this is, in fact, a very young surface.'"

Farley says his involvement with MSL is a major departure from his previous work, as he has not been heavily involved in the study of the geology of Mars. "Most of what I do is technique development," he says. "So it's interesting for me to see potential application of one of those techniques in another very different setting."

In contrast, space missions are Ehlmann's bread and butter. She got her first taste of rover operations while an undergraduate student working on the Mars Exploration Rovers mission. Then as a graduate student, she was a collaborator on the Mars Reconnaissance Orbiter mission and used data from multiple orbiters to locate hydrated minerals on the surface of the red planet.

For MSL, Ehlmann proposed to help improve the team's ability to select rocks from a distance for more extensive study. Curiosity is equipped with a laser and a telescope known collectively as ChemCam, mounted on its mast. From a distance of about seven meters, the laser can zap a rock to create a plasma, which can be analyzed with the ChemCam spectrometer to get a sense of the chemical elements present. The science team needs to be able to use those results and their knowledge of mineralogy to quickly decide whether to spend more time and energy on a particular target or to keep Curiosity moving.

To give them a leg up, Ehlmann is analyzing rocks from places such as Iceland as well as synthetic mixtures of minerals in the lab that are similar to the materials observed from Mars orbit at the Gale Crater landing site. The rocks can be well characterized in Earth laboratories to understand their mineralogy, the elements they are made of, and how they would appear from orbit. She is studying how they have been changed by different types of interaction with water. She plans to take the samples to Los Alamos National Laboratory, which partnered with the French national space agency to build the ChemCam, in order to test her samples with a ChemCam-like instrument.

"It's very helpful to have this beforehand understanding of what you might see or what kinds of analyses you need to run," Ehlmann says. "If you understand the processes enough that you develop quick-look algorithms for detecting different styles of alteration, it will help in the tactical timescale when you only have a few hours to come up with a plan for the rover for the next day."

Writer: 
Marcus Woo
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

An Earthquake in a Maze

Caltech researchers provide highest-resolution observations yet of the complex 2012 Sumatra earthquake

PASADENA, Calif.—The powerful magnitude-8.6 earthquake that shook Sumatra on April 11, 2012, was a seismic standout for many reasons, not the least of which is that it was larger than scientists thought an earthquake of its type—an intraplate strike-slip quake—could ever be. Now, as Caltech researchers report on their findings from the first high-resolution observations of the underwater temblor, they point out that the earthquake was also unusually complex—rupturing along multiple faults that lie at nearly right angles to one another, as though racing through a maze.

The new details provide fresh insights into the possibility of ruptures involving multiple faults occurring elsewhere—something that could be important for earthquake-hazard assessment along California's San Andreas fault, which itself is made up of many different segments and is intersected by a number of other faults at right angles.

"Our results indicate that the earthquake rupture followed an exceptionally tortuous path, breaking multiple segments of a previously unrecognized network of perpendicular faults," says Jean-Paul Ampuero, an assistant professor of seismology at Caltech and one of the authors of the report, which appears online today in Science Express. "This earthquake provided a rare opportunity to investigate the physics of such extreme events and to probe the mechanical properties of Earth's materials deep beneath the oceans."

Most mega-earthquakes occur at the boundaries between tectonic plates, as one plate sinks beneath another. The 2012 Sumatra earthquake is the largest earthquake ever documented that occurred away from such a boundary—a so-called intraplate quake. It is also the largest that has taken place on a strike-slip fault—the type of fault where the land on either side is pushing horizontally past the other.

The earthquake happened far offshore, beneath the Indian Ocean, where there are no geophysical monitoring sensors in place. Therefore, the researchers used ground-motion recordings gathered by networks of sensors in Europe and Japan, and an advanced source-imaging technique developed in Caltech's Seismological Laboratory as well as the Tectonics Observatory to piece together a picture of the earthquake's rupture process. 

Lingsen Meng, the paper's lead author and a graduate student in Ampuero's group, explains that technique by comparing it with how, when standing in a room with your eyes closed, you can often still sense when someone speaking is walking across the room. "That's because your ears measure the delays between arriving sounds," Meng says. "Our technique uses a similar idea. We measure the delays between different seismic sensors that are recording the seismic movements at set locations." Researchers can then use that information to determine the location of a rupture at different times during an earthquake. Recent developments of the method are akin to tracking multiple moving speakers in a cocktail party.

Using this technique, the researchers determined that the three-minute-long Sumatra earthquake involved at least three different fault planes, with a rupture propagating in both directions, jumping to a perpendicular fault plane, and then branching to another.

"Based on our previous understanding, you wouldn't predict that the rupture would take these bends, which were almost right angles," says Victor Tsai, an assistant professor of geophysics at Caltech and a coauthor on the new paper. 

The team also determined that the rupture reached unusual depths for this type of earthquake—diving as deep as 60 kilometers in places and delving beneath the Earth's crust into the upper mantle. This is surprising given that, at such depths, pressure and temperature increase, making the rock more ductile and less apt to fail. It has therefore been thought that if a stress were applied to such rocks, they would not react as abruptly as more brittle materials in the crust would. However, given the maze-like rupture pattern of the earthquake, the researchers believe another mechanism might be in play.

"One possible explanation for the complicated rupture is there might have been reduced friction as a result of interactions between water and the deep oceanic rocks," says Tsai. "And," he says, "if there wasn't much friction on these faults, then it's possible that they would slip this way under certain stress conditions."

Adding to the list of the quake's surprising qualities, the researchers pinpointed the rupture to a region of the seafloor where seismologists had previously considered such large earthquakes unlikely based on the geometry of identified faults. When they compared the location they had determined using source-imaging with high-resolution sonar data of the topography of the seafloor, the team found that the earthquake did not involve what they call "the usual suspect faults."

"This part of the oceanic plate has fracture zones and other structures inherited from when the seafloor formed here, over 50 million years ago," says Joann Stock, professor of geology at Caltech and another coauthor on the paper. "However, surprisingly, this earthquake just ruptured across these features, as if the older structure didn't matter at all."

Meng emphasizes that it is important to learn such details from previous earthquakes in order to improve earthquake-hazard assessment. After all, he says, "If other earthquake ruptures are able to go this deep or to connect as many fault segments as this earthquake did, they might also be very large and cause significant damage."

Along with Meng, Ampuero, Tsai, and Stock, additional Caltech coauthors on the paper, "An earthquake in a maze: compressional rupture branching during the April 11 2012 M8.6 Sumatra earthquake," are postdoctoral scholar Zacharie Duputel and graduate student Yingdi Luo. The work was supported by the National Science Foundation, the Gordon and Betty Moore Foundation, and the Southern California Earthquake Center, which is funded by the National Science Foundation and the United States Geological Survey.

Writer: 
Kimm Fesenmaier
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

Geological Society of America Awards Eiler

John Eiler, Robert P. Sharp Professor of Geology and professor of geochemistry at Caltech, has been awarded the 2012 Arthur L. Day Medal by the Geological Society of America (GSA).

Arthur Louis Day established the award in 1948 for "outstanding distinction in contributing to geologic knowledge through the application of physics and chemistry to the solution of geologic problems."

Eiler will receive the medal at the GSA's annual meeting, which will be held November 4–9 in Charlotte, North Carolina.

Writer: 
Allison Benter
Writer: 
Exclude from News Hub: 
Yes

Caltech Scientists Find New Primitive Mineral in Meteorite

PASADENA, Calif.—In 1969, an exploding fireball tore through the sky over Mexico, scattering thousands of pieces of meteorite across the state of Chihuahua. More than 40 years later, the Allende meteorite is still serving the scientific community as a rich source of information about the early stages of our solar system's evolution. Recently, scientists from the California Institute of Technology (Caltech) discovered a new mineral embedded in the space rock—one they believe to be among the oldest minerals formed in the solar system.

Dubbed panguite, the new titanium oxide is named after Pan Gu, the giant from ancient Chinese mythology who established the world by separating yin from yang to create the earth and the sky. The mineral and the mineral name have been approved by the International Mineralogical Association's Commission on New Minerals, Nomenclature and Classification. A paper outlining the discovery and the properties of this new mineral will be published in the July issue of the journal American Mineralogist, and is available online now.

"Panguite is an especially exciting discovery since it is not only a new mineral, but also a material previously unknown to science," says Chi Ma, a senior scientist and director of the Geological and Planetary Sciences division's Analytical Facility at Caltech and corresponding author on the paper.

The Allende meteorite is the largest carbonaceous chondrite—a diverse class of primitive meteorites—ever found on our planet and is considered by many the best-studied meteorite in history. As a result of an ongoing nanomineralogy investigation of primitive meteorites—which Ma has been leading since 2007—nine new minerals, including panguite, have been found in the Allende meteorite. Some of those new finds include the minerals allendeite, hexamolybdenum, tistarite, and kangite. Nanomineralogy looks at tiny particles of minerals and the minuscule features within those minerals.

"The intensive studies of objects in this meteorite have had a tremendous influence on current thinking about processes, timing, and chemistry in the primitive solar nebula and small planetary bodies," says coauthor George Rossman, the Eleanor and John R. McMillan Professor of Mineralogy at Caltech.

Panguite was observed first under a scanning electron microscope in an ultra-refractory inclusion embedded in the meteorite. Refractory inclusions are among the first solid objects formed in our solar system, dating back to before the formation of Earth and the other planets. "Refractory" refers to the fact that these inclusions contain minerals that are stable at high temperatures and in extreme environments, which attests to their likely formation as primitive, high-temperature liquids produced by the solar nebula.

According to Ma, studies of panguite and other newly discovered refractory minerals are continuing in an effort to learn more about the conditions under which they formed and subsequently evolved. "Such investigations are essential to understand the origins of our solar system," he says.

Additional authors on the American Mineralogist paper, "Panguite, (Ti4+,Sc,Al,Mg,Zr,Ca)1.8O3, a new ultra-refractory titania mineral from the Allende meteorite: Synchrotron micro-diffraction and EBSD," are John R. Beckett, senior research scientist at Caltech; Oliver Tschauner from the University of Nevada–Las Vegas; and Wenjun Liu from the Argonne National Laboratory. The study was supported through grants from the National Science Foundation, the U.S. Department of Energy, and NASA's Office of Space Science.  

Writer: 
Katie Neith
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

Notes from the Back Row: "The Isotope Time Machine"

Were dinosaurs slow and stupid, as used to be the prevailing wisdom, or nimble and smart enough to eat an attorney, as in the 1993 film Jurassic Park? The answer depends largely on whether the T. Rex in question is cold blooded, like an alligator—although gators, in a shocking lack of professional courtesy, are fully capable of chowing down on counsel—or warm blooded, like a bird. This is because creatures capable of maintaining a constant body temperature, regardless of their environment, generally also have the energy to move fast and think quickly. There's only one sure way to settle the debate, but taking the temperature of an animal that's been extinct for 150 million years poses certain obvious problems.

Fortunately, John Eiler, the Robert P. Sharp Professor of Geology and professor of geochemistry, has mastered the art of time travel without leaving the lab. His time machine is a mass spectrometer, a device that separates atoms of different weights in a process he likens to the workings of "a good, old-fashioned television set from the days when TV sets were the size of smart cars." Atoms of a given element that have different weights are called isotopes, and in his Watson Lecture on February 29, 2012, Eiler shows how isotope analysis can not only take a dinosaur's temperature, but perhaps tell us why they died. It's CSI: Jurassic Park.

"The Isotope Time Machine" is available for download in HD from Caltech on iTunesU. (Episode 9)

Writer: 
Doug Smith
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Caltech Astronomer Mike Brown Awarded Kavli Prize in Astrophysics

PASADENA, Calif.—Mike Brown, the Richard and Barbara Rosenberg Professor and professor of planetary astronomy at the California Institute of Technology (Caltech), has been named a co-winner of the 2012 Kavli Prize in Astrophysics for his efforts to understand the outer solar system—work that led to the demotion of Pluto.

Brown shares the award with David Jewitt (MS '80, PhD '83) of UCLA and Jane Luu of MIT's Lincoln Laboratory; in 1992, Jewitt and Luu discovered the first object in the Kuiper belt, a collection of more than a thousand objects beyond the orbit of Neptune. Brown, who joined Caltech's faculty in 1997, has since become a leader in the search for planet-sized objects in the Kuiper belt. According to the prize citation, the three received the prize "for discovering and characterizing the Kuiper belt and its largest members, work that led to a major advance in the understanding of the history of our planetary system."

Brown's most well-known discovery came in 2005, when he found a Kuiper-belt object, later named Eris, that is about the same size as Pluto but 27 percent more massive. That finding caused astronomers to rethink the definition of a planet, resulting in the reclassification of Pluto as a dwarf planet.

"Mike spent years acquiring a massive number of images and learning how to process them to accurately detect objects that subtly shift in the sky over successive days—without knowing whether there was anything interesting to be discovered," explains Kenneth Farley, the W.M. Keck Foundation Professor of Geochemistry and chair of the Division of Geological and Planetary Sciences. "But that dedication was rewarded by the discovery of several fascinating Kuiper-belt objects, and just as important as their discovery was Mike's effort in understanding them—where they came from, how they formed, what they are made of, and what they tell us about our solar system. It is wonderful to see Mike recognized for these contributions."

"This distinguished prize is further acknowledgment of Mike's extraordinary accomplishments and pioneering research that has literally reshaped our understanding of the solar system," adds Caltech president Jean-Lou Chameau. "He is truly a 'renaissance scientist' who approaches teaching and scientific discovery with passion and charisma. We are proud of Mike and are privileged to have him on the Caltech faculty."

"It's humbling to be included alongside previous Kavli Prize winners, from the people whose incredible designs for telescopes enable all of us to make these discoveries to the very pioneers of astrophysics," says Brown. "And it's an amazing reminder that some of the mysteries of the universe are right here in our own cosmic backyard."

The Kavli Prize, which includes a scroll, a gold medal, and $1 million, recognizes scientists in astrophysics, nanoscience, and neuroscience, and has been awarded every other year since 2008. King Harald of Norway will present the prizes to the winners at a ceremony in Oslo on September 4. Caltech's Maarten Schmidt, the Francis L. Moseley Professor of Astronomy, Emeritus, won the astrophysics prize in 2008. Past winners who are Caltech alumni include Jerry Nelson (BS '65), Roger Angel (MS '66), and Richard Scheller (PhD '80).

The Kavli Prizes were initiated by and named after Fred Kavli, founder and chairman of the Kavli Foundation, which is dedicated to advancing science for the benefit of humanity, promoting public understanding of scientific research, and supporting scientists and their work.

Writer: 
Marcus Woo
Writer: 
Exclude from News Hub: 
No
News Type: 
In Our Community

Caltech Researchers Gain Greater Insight into Earthquake Cycles

New dynamic computer model first to show full history of a fault segment

PASADENA, Calif.—For those who study earthquakes, one major challenge has been trying to understand all the physics of a fault—both during an earthquake and at times of "rest"—in order to know more about how a particular region may behave in the future. Now, researchers at the California Institute of Technology (Caltech) have developed the first computer model of an earthquake-producing fault segment that reproduces, in a single physical framework, the available observations of both the fault's seismic (fast) and aseismic (slow) behavior. 

"Our study describes a methodology to assimilate geologic, seismologic, and geodetic data surrounding a seismic fault to form a physical model of the cycle of earthquakes that has predictive power," says Sylvain Barbot, a postdoctoral scholar in geology at Caltech and lead author of the study.

A paper describing their model—the result of a Caltech Tectonics Observatory (TO) collaborative study by geologists and geophysicists from the Institute's Division of Geological and Planetary Sciences and engineers from the Division of Engineering and Applied Science—appears in the May 11 edition of the journal Science.

"Previous research has mostly either concentrated on the dynamic rupture that produces ground shaking or on the long periods between earthquakes, which are characterized by slow tectonic loading and associated slow motions—but not on both at the same time," explains study coauthor Nadia Lapusta, professor of mechanical engineering and geophysics at Caltech. Her research group developed the numerical methods used in making the new model. "In our study, we model the entire history of an earthquake-producing fault and the interaction between the fast and slow deformation phases."

Using previous observations and laboratory findings, the team—which also included coauthor Jean-Philippe Avouac, director of the TO—modeled an active region of the San Andreas Fault called the Parkfield segment. Located in central California, Parkfield produces magnitude-6 earthquakes every 20 years on average. They successfully created a series of earthquakes (ranging from magnitude 2 to 6) within the computer model, producing fault slip before, during, and after the earthquakes that closely matched the behavior observed in the past fifty years. 

"Our model explains some aspects of the seismic cycle at Parkfield that had eluded us, such as what causes changes in the amount of time between significant earthquakes and the jump in location where earthquakes nucleate, or begin," says Barbot.

The paper also demonstrates that a physical model of fault-slip evolution, based on laboratory experiments that measure how rock materials deform in the fault core, can explain many aspects of the earthquake cycle—and does so on a range of time scales. "Earthquake science is on the verge of building models that are based on the actual response of the rock materials as measured in the lab—models that can be tailored to reproduce a broad range of available observations for a given region," says Lapusta. "This implies we are getting closer to understanding the physical laws that govern how earthquakes nucleate, propagate, and arrest."

She says that they may be able to use models much like the one described in the Science paper to forecast the range of potential earthquakes on a fault segment, which could be used to further assess seismic hazard and improve building designs. 

Avouac agrees. "Currently, seismic hazard studies rely on what is known about past earthquakes," he says. "However, the relatively short recorded history may not be representative of all possibilities, especially rare extreme events. This gap can be filled with physical models that can be continuously improved as we learn more about earthquakes and laws that govern them."

"As computational resources and methods improve, dynamic simulations of even more realistic earthquake scenarios, with full account for dynamic interactions among faults, will be possible," adds Barbot. 

The Science study, "Under the Hood of the Earthquake Machine; Toward Predictive Modeling of the Seismic Cycle," was funded by grants from the Gordon and Betty Moore Foundation, the National Science Foundation, and the Southern California Earthquake Center.

Writer: 
Katie Neith
Writer: 
Exclude from News Hub: 
No
News Type: 
Research News

Pages

Subscribe to RSS - GPS