Researchers find new clue why Martian wateris found on the north pole, not the south

When astronauts finally land on Mars, a safe bet is that they'll head for northern climes if they intend to spend much time there. That's because nearly all the available water is frozen as ice at the north pole. Planetary scientists have been aware of this for some time, but they now have a new clue why it is so.

In the March 21 issue of the journal Nature, California Institute of Technology researcher Mark Richardson and his colleague John Wilson of the National Oceanic and Atmospheric Administration reveal that the higher average elevation of the Red Planet's southern hemisphere ultimately tends to drive water northward.

Their evidence is based on a computer model the two have worked on for years (Wilson since 1992, Richardson since 1996), coupled with data returned by NASA's Mars Global Surveyor.

"We've found a mechanism in the Martian climate that introduces annual average hemispheric asymmetry," explains Richardson, an assistant professor of planetary science at Caltech. "The circulation systems of Mars and Earth are similar in certain ways, but Mars is different in that water is not available everywhere."

The key to understanding the phenomenon is a complicated computer modeling of the Hadley circulation, which extends about 40 degrees of latitude each side of the Martian equator. A topographical bias in circulation pretty much means there will be a bias in the net pole-to-pole transport of water, Richardson explains.

A plausible explanation is that water ice is found at the north pole and carbon dioxide ice is found at the south for reasons having to do with the way the sun heats the atmosphere. As the Martian orbit changes on time scales of 50,000 years and more, these effects tend to cancel, with no pole claiming the water ice cap over geological time. It has been suggested that topography determines where carbon dioxide forms, and hence, where water ice can form, but the processes controlling carbon dioxide ice caps are poorly understood.

However, the mechanism Richardson and Wilson describe is independent of this occasional realignment of the pole's precession and the planet's eccentric orbit. The mechanism means that, while there is never a time in the past when water ice can be discounted at the south pole, one is more likely to find it more frequently at the north pole.

The importance of the study is its furthering of our understanding of the Martian climate and Martian water cycle. A better understanding of how water is transported will be particularly important to determining whether life once existed on Mars, and what happened to it if it ever did.

The Web address for the journal Nature is http://www.nature.com.

Contact: Robert Tindol (626) 395-3631

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Caltech astronomer to search for "hot Jupiters"with off-the-shelf camera lens

In an age when nearly all astronomical work requires really big telescopes, David Charbonneau is something of an anomaly. The Caltech astronomer will soon begin a multiyear survey for extrasolar planets at Palomar Observatory—not with the 200-inch Hale telescope, but with a tiny desktop-sized device he and JPL researcher John Trauger assembled largely from parts bought at a camera shop.

Basing his instrument on a standard 300-millimeter telephoto lens for a 35-millimeter camera, Charbonneau will begin sweeping the skies this spring in hopes of catching a slew of "hot Jupiters" as their fast orbits take them in front of other stars. Admittedly, the charge-coupled device at the camera-end of the lens is a good bit more costly than the lens itself, but the total budget for the project—$100,000—is still a paltry sum when one considers that the next generation of earthbound telescopes will likely cost upwards of $400 million apiece.

Charbonneau, a recent import to the Caltech astronomy staff from the Harvard-Smithsonian Center for Astrophysics, is one of the world's leading authorities on the search for "transiting planets," or planets that should be detectable as they pass into the line of sight between their host star and Earth. In November, Charbonneau and his colleagues made international news when they discovered the first planetary atmosphere outside our own solar system. But that work was done with the Hubble Space Telescope. The yet-to-be-formally-named telescope at Palomar Observatory will certainly be more modest in cost, but every bit as ambitious a program for searching out other worlds.

"Basically, the philosophy of this project is that, if we can buy the stuff we need off the shelf, we'll buy it," the Canadian native said recently in his new campus office.

At the fore-end of the new instrument is a standard 300-millimeter camera lens. Charbonneau settled on a telephoto lens because he reasoned that the optics have been honed to a fine degree of precision over the years. Too, he assumed that the lens would be robust enough for the duration of the three-year project.

The charge-coupled device (CCD), a standard imaging tool in astronomy for the last couple of decades, is a $22,000 item that accounts for the largest part of the instrument budget. The CCD will be mounted in a specially constructed camera housing to fit at the back of the lens, and the entire device will be fitted onto an inexpensive equatorial mount—also available at many stores carrying amateur astronomical equipment.

Meanwhile, the Palomar staff has stored away a 20-inch telescope so Charbonneau will have a small dome for his new instrument, and are also doing other preparations to mechanize the actual observing so that a telescope operator will not have to be on site at all times.

Palomar Observatory engineer Hal Petrie says the mountain crew is currently busy linking the new telescope with an existing weather-monitoring system at the nearby 48-inch dome, where another automated telescope is located. The system monitors the atmospheric conditions to determine whether the dome should be opened.

"The new telescope is a very good use of space," says Petrie. "The potential for results is very exciting."

Charbonneau will be able to photograph a single square of sky, about 5 degrees by 5 degrees. That's a field of view in which about 100 full moons could fit. Or, if one prefers, a field of view in which an entire constellation can be seen at one time.

With special software Charbonneau helped develop during his time at Harvard-Smithsonian and at the National Center for Atmospheric Research, he will compare many pictures of the same patch of sky to see if any of the thousands of stars in each field have slightly changed. If the software turns up a star that has dimmed slightly, the reason could well be that a planet passed in front of the star between exposures.

Repeated measurements will allow Charbonneau to measure the orbital period and physical size of each planet, and further work with the 10-meter telescopes at the Keck Observatory will allow him and his colleagues to get spectrographic data, and thus, the mass and composition of each planet.

"Once you get the mass and size, you have the density," he says. Weather permitting, Charbonneau will be able to get up to 300 images during an ideal night. Assuming that he can have 20 good nights per month, he should have about 6,000 images each month show up in his computer.

The ideal time will be in the fall and winter, when the Milky Way is in view, and an extremely high number of stars can be squeezed into each photograph. This, too, is an anomaly in astrophysical research, particularly to cosmologists, for whom the Milky Way is pretty much a blocked view of the deep sky.

"It's estimated that about one in three stars in our field of view will be like the sun, and that one percent of sunlike stars will have a hot Jupiter, or a gas giant that is so close to the star that its orbit is about four or five days," he says.

"One-tenth of this 1 percent will be inclined in the right direction so that the planet will pass in front of its star, so that maybe one in 3,000 stars will have a planet we can detect," Charbonneau adds. "Or if you want to be conservative, about one in 6,000."

Compared to other research programs in astronomy, the search for hot Jupiters is fairly simple and straightforward to explain to the public, Charbonneau says.

"An amateur could do this, except maybe for the debugging of the software, which requires several people working 10 hours a day.

"But it's easy to understand what's going on, and cheap to build the equipment. That's why everyone thinks it's an ideal project—if it works."

The new Palomar telescope is the final instrument in a network of three. Of the other two, one is located in the Canary Islands and operated by the National Center for Atmospheric Research; the other is near Flagstaff, Arizona, and is operated by Lowell Observatory.

The large span in longitude of the three-instrument network will allow Charbonneau and his colleagues to observe a patch of sky with one telescope while the patch is above the horizon in the night sky, and then pass it off to the next westward telescope as the sun comes up.

Contact: Robert Tindol (626) 395-3631

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Caltech's Joseph Kirschvink Receives Feynman Prize for Excellence in Teaching

"I was shocked and stunned," laughed Joseph Kirschvink, a professor of geobiology at the California Institute of Technology, upon hearing he had been awarded the 2002 Richard P. Feynman Prize for Excellence in Teaching. But, to hear his students tell it, it's clear the honor is an appropriate one.

Indeed, Kirschvink was nominated by two of his current students, Ben Weiss, who will graduate with his Ph.D. in planetary science in 2002, and Tim Raub, a forthcoming 2002 graduate (BS, geology; MS, geobiology). In their nominating letter, they point out that among undergrads, Kirschvink's stature is "legendary," and his earth history and introduction to geobiology classes are popular even among non-majors. "This popularity," they wrote, "reflects Joe's fundamental teaching philosophy: he treats students like colleagues."

To his students it is "Joe," not Dr. Kirschvink. The informality invites questions, they write, and it is those questions that Kirschvink thrives on. Students may interrupt him at any time, and he explains and re-explains concepts, holding to a standard of unanimous understanding among his pupil-colleagues. "Joe's unique philosophy echoes Caltech's purpose to create the 100th scientist," wrote Weiss and Raub, "yet it combines this, successfully, with the noble and perhaps even more difficult goal to 'leave no student behind.' "

The Feynman Prize is presented each year to a Caltech professor who demonstrates exceptional ability, creativity, and innovation in both laboratory and classroom instruction. It consists of a cash award of $3,500, matched by an equivalent raise in the annual salary of the awardee. Kirschvink was specifically selected, said Caltech provost Steve Koonin, for "his innovative teaching style and outstanding mentorship, which have inspired a generation of Caltech students."

Kirschvink believes it was his own experience as a Caltech alum—BS and MS in 1975—that contributes to his classroom rapport. "As an undergrad here I know the capabilities of the students," he says. In all his classes, he employs the Socratic method of doubting and questioning statements. It's a technique he learned, he says, from the late Gene Shoemaker (codiscoverer of the Shoemaker-Levy comet that hit Jupiter) one of his professors from his own days as an undergrad.

Kirschvink frequently gets his undergraduates involved in his science projects as well. His research is aimed at increasing our understanding of how biological evolution has influenced, and has been influenced by, major events on the surface of the earth. His major contributions include the "snowball" Earth theory, the theory that the entire Earth may have actually frozen over several times in its history, potentially causing some of the most severe crises in the history of life on Earth, and perhaps stimulating evolution. Another original concept concerns the Cambrian evolutionary explosion, that he believes may have been precipitated in part by a large burst of true polar wander, in which the earth's rotational axis moved to the equator in a geologically short interval of time. The common thread in his research efforts is the study of paleomagnetism and rock magnetism, for which Kirschvink maintains laboratories dedicated to the study of weakly magnetic biological and geological materials.

The Feynman Prize is made possible by the generosity of an endowment from Ione and Robert E. Paradise, along with additional contributions from Mr. and Mrs. William H. Hurt. It is named in honor of the late Caltech Nobel laureate and popular science author, who was lauded for his innovative classroom lectures on physics.

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Caltech Professor Emeritus Receives Prestigious German Scientific Honor

PASADENA, Calif.— Peter Wyllie, professor of geology, emeritus, at the California Institute of Technology, recently received the Leopold von Buch Medal, one of the highest scientific awards presented by the German Geological Society. This award, which was presented during the annual meeting in Kiel, Germany, is accompanied by honorary membership in the German Geological Society.

The Leopold von Buch Medal is awarded annually, usually to a foreign scholar in recognition of outstanding scientific contributions and for special services to the geological sciences.

Wyllie received the medal "in recognition of his scientific research on the petrology of crystalline rocks, and also for his service in publicizing the importance of the geosciences for society."

Wyllie is an internationally known authority on the formation of igneous rocks—those created when molten material solidifies. His primary research covers experimental petrology of magmas and volatiles that erupt as lavas from volcanoes or form the granites of the Sierra Nevada Mountains.

Throughout his career, Wyllie has been a "global ambassador" for the geosciences. He served as chairman of the U.S. National Academy committee that published, in 1993, the first national survey of Earth sciences, Solid-Earth Sciences and Society. Wyllie has given numerous international lectures on the impact of Earth sciences on society, including such subjects as resources (oil, minerals, and water supply), hazards (earthquakes, volcanic eruptions, and landslides), and global climatic change. He has been elected fellow or foreign member of national science academies in the United States, the United Kingdom (the Royal Society), Russia, China, and India (Delhi and Allahabad), and of Academia Europaea.

He has served as president of the Mineralogical Society of America, the International Mineralogical Association, and the International Union of Geodesy and Geophysics.

Wyllie has received numerous honors and awards throughout his career, including the 2001 Mineralogical Society of America's Roebling Medal, the Wollaston Medal of the Geological Society of London in 1982, and the Abraham-Gottlob-Werner Medaille of the German Mineralogical Society in 1987.

Wyllie joined Caltech in 1983 as chair of the Division of Geological and Planetary Sciences. In 1987, Wyllie returned to teaching and research, then was appointed division academic officer in 1994. He served in this capacity until his retirement in 1999.

Contact: Deborah Williams-Hedges (626) 395-3227 debwms@caltech.edu

Visit the Caltech Media Relations Web site at: http://pr.caltech.edu/media

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Astronomers detect atmosphereof planet outside solar system

Astronomers using NASA's Hubble Space Telescope have made the first direct detection of the atmosphere of a planet orbiting a star outside our solar system and have obtained the first information about its chemical composition. Their unique observations demonstrate that it is possible with Hubble and other telescopes to measure the chemical makeup of extrasolar planet atmospheres and to potentially search for chemical markers of life beyond Earth.

The planet orbits a yellow, sunlike star called HD 209458, a seventh-magnitude star (visible through an amateur telescope), which lies 150 light-years away in the autumn constellation Pegasus. Its atmospheric composition was probed when the planet passed in front of its parent star, allowing astronomers for the first time ever to see light from the star filtered through the planet's atmosphere.

Lead investigator David Charbonneau of the California Institute of Technology and the Harvard-Smithsonian Center for Astrophysics, Timothy Brown of the National Center for Atmospheric Research, and colleagues used Hubble's spectrometer (the Space Telescope Imaging Spectrograph) to detect the presence of sodium in the planet's atmosphere.

"This opens up an exciting new phase of extrasolar planet exploration, where we can begin to compare and contrast the atmospheres of planets around other stars," says Charbonneau. The astronomers actually saw less sodium than predicted for the Jupiter-class planet, leading to one interpretation that high-altitude clouds in the alien atmosphere may have blocked some of the light. The findings will be published in the Astrophysical Journal.

The Hubble observation was not tuned to look for gases expected in a life-sustaining atmosphere (which is improbable for a planet as hot as the one observed). Nevertheless, this unique observing technique opens a new phase in the exploration of extrasolar planets, say astronomers.

Such observations could potentially provide the first direct evidence for life beyond Earth by measuring unusual abundances of atmospheric gases caused by the presence of living organisms. The planet orbiting HD 209458 was discovered in 1999 through its slight gravitational tug on the star. Based on that observation the planet is estimated to be 70 percent the mass of the giant planet Jupiter (or 220 times more massive than Earth).

Subsequently, astronomers discovered the planet passes in front of the star, causing the star to dim very slightly for the transit's duration. This means the planet's orbit happens to be tilted edge-on to our line-of-sight from Earth. It is the only example of a transit among all the extrasolar planets discovered to date.

The planet is an ideal target for repeat observations because it transits the star every 3.5 days—which is the extremely short amount of time it takes the planet to whirl around the star at a distance of merely 4 million miles from the star's searing surface. This precariously close proximity to the star heats the planet's atmosphere to a torrid 2,000 degrees Fahrenheit (1,100 degrees Celsius).

Previous transit observations by Hubble and ground-based telescopes confirmed that the planet is primarily gaseous, rather than liquid or solid, because it has a density less than that of water. (Earth, a rocky rather than a gaseous planet, has an average density five times that of water.) These earlier observations thus established that the planet is a gas giant, like Jupiter and Saturn.

The planet's swift orbit allowed for observations of four separate transits to be made by Hubble in search of direct evidence of an atmosphere. During each transit a small fraction of the star's light passed through the planet's atmosphere on its way to Earth. When the color of the light was analyzed by a spectrograph, the telltale "fingerprint" of sodium was detected. Though the star also has sodium in its outer layers, the STIS precisely measured the added influence of sodium in the planet's atmosphere.

The team—including Robert Noyes of the Harvard-Smithsonian Center for Astrophysics and Ronald Gilliland of the Space Telescope Science Institute in Baltimore, Maryland—next plans to look at HD 209458 again with Hubble, in other colors of the star's spectrum to see which are filtered by the planet's atmosphere. They hope eventually to detect methane, water vapor, potassium, and other chemicals in the planet's atmosphere. Once other transiting giants are found in the next few years, the team expects to characterize chemical differences among the atmospheres of these planets.

These anticipated findings would ultimately help astronomers better understand a bizarre class of extrasolar planets discovered in recent years that are dubbed "hot Jupiters." They are the size of Jupiter but orbit closer to their stars than the tiny innermost planet Mercury in our solar system. While Mercury is a scorched rock, these planets have enough gravity to hold onto their atmospheres, though some are hot enough to melt copper.

Conventional theory is that these giant planets could not have been born so close to their stars. Gravitational interactions with other planetary bodies or gravitational forces in a circumstellar disk must have carried these giants via spiraling orbits precariously close to their stars from their birthplace farther out, where they bulked up on gas and dust as they formed.

Proposed moderate-sized U.S. and European space telescopes could allow for the detection of many much smaller Earth-like planets by transit techniques within the next decade. The chances for detection will be more challenging, since detecting a planet orbiting at an Earth-like distance will mean a much tighter orbital alignment is needed for a transit. And the transits would be much less frequent for planets with an orbital period of a year, rather than days. Eventually, study of the atmosphere of these Earth-like planets will require meticulous measurements by future larger space telescopes.

The Space Telescope Science Institute (STScI) is operated by the Association of Universities for Research in Astronomy (AURA), for NASA, under contract with the Goddard Space Flight Center, Greenbelt, Maryland. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA). The National Center for Atmospheric Research's primary sponsor is the National Science Foundation.

Contact: Robert Tindol (626) 395-3631

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Caltech Professor Emeritus Receives Roebling Medal

PASADENA, Calif.— Former heavyweight boxing champion and dog-sled driver Peter Wyllie is adding a new accomplishment to his list of achievements—he has received the highest United States award in mineralogy. Wyllie, now a professor of geology, emeritus, at the California Institute of Technology, is the 2001 recipient of the Mineralogical Society of America's Roebling Medal, which is awarded for "scientific eminence as represented primarily by scientific publication of outstanding original research in mineralogy." The only other Caltech faculty member to receive this medal was Linus Pauling in 1967.

Wyllie is an internationally known authority on the formation of igneous rocks—those created when molten material solidifies. His research covered experimental petrology of magmas and volatiles. He was particularly involved in studying the origin of lavas like those erupted from Mount St. Helens in 1980; granites that form the core of mountain ranges such as the Sierra Nevada; kimberlites, which transport diamonds to the earth's surface; and carbonatites, peculiar igneous rocks that look like limestones and contain useful mineral resources.

In 1948, Wyllie joined the Royal Air Force. It was there that he pursued the sport of boxing, and earned the title of 1949 Royal Air Force (Scotland) heavyweight boxing champion.

After serving in the armed forces, Wyllie attended the University of St. Andrews in Scotland, where he earned his BSc in geology and physics in 1952.

Later in 1952, Wyllie drove a team of huskies through the frozen, unexplored mountains in Dronning Louise Land, serving as an assistant field geologist with the British North Greenland Expedition. For two years, from 1952 to 1954, including two long, dark winters without sunlight, expedition members were isolated in the frigid arctic. For his role in the expedition, Wyllie received the Polar Medal from Queen Elizabeth. He then returned to the University of St. Andrews, earning his PhD in geology in 1958.

Wyllie has taught at the University of St. Andrews, Penn State, and Leeds University in England. He was department chair at the University of Chicago prior to joining Caltech in 1983 as chair of the Division of Geological and Planetary Sciences. In 1987, Wyllie returned to teaching and research, then was appointed division academic officer in 1994. He served in this capacity until his retirement in 1999.

He has served as president of the Mineralogical Society of America, the International Mineralogical Association, and the International Union of Geodesy and Geophysics. Wyllie has been elected as fellow or foreign member of seven national science academies, in the United States, the United Kingdom (Royal Society), Russia, China, India (Delhi and Allahabad), and Europe.

The author of three books, including two basic textbooks, Wyllie has published more than 300 scientific articles. He was chairman of the U.S. National Academy committee that published the first national disciplinary survey of earth sciences in 1993, Solid-Earth Sciences and Society. This volume was described by the director of the U.S. Geological Survey, Gordon Eaton, as "a road map for the future of our science that should and will guide significant decisions concerning strategic planning for and funding in support of research, as well as long needed and overdue revisions of Earth-science curricula across the nation."

Wyllie has received numerous distinguished honors and awards throughout his career, including the Wollaston Medal of the Geological Society of London in 1982, and the Abraham-Gottlob-Werner Medaille of the German Mineralogical Society in 1987.

The Roebling Medal, established in 1937 by the Mineralogical Society of America, signifies the highest recognition of achievement mineralogy can bestow. The Mineralogical Society of America was founded in 1919 for the advancement of mineralogy, crystallography, geochemistry, and petrology, and for the promotion of their uses in other sciences, industry, and the arts. It encourages fundamental research about natural materials; supports the teaching of mineralogical concepts and procedures to students of mineralogy and related sciences; and attempts to raise the scientific literacy of society with respect to issues involving mineralogy. The society encourages the general preservation of mineral collections, displays, mineral localities, type minerals, and scientific data.

Contact: Deborah Williams-Hedges (626) 395-3227 debwms@caltech.edu

Visit the Caltech Media Relations Web site at: http://pr.caltech.edu/media

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Life rebounded quickly after collision 65 million years ago that wiped out dinosaurs

Though the dinosaurs fared poorly in the comet or meteor impact that destroyed two-thirds of all living species 65 million years ago, new evidence shows that various other forms of life rebounded from the catastrophe in a remarkably short period of time.

In the March 9 issue of the journal Science, a team of geochemists reports that life was indeed virtually wiped out for a period of time, but then reappeared just as abruptly only 10,000 years after the initial collision. Further, the evidence shows that the extinctions 65 million years ago, which mark the geologic time known as the Cretaceous-Tertiary (K-T) boundary, were most likely caused by a single catastrophic impact.

"There's been a longstanding debate whether the mass extinctions at the K-T boundary were caused by a single impact or maybe a swarm of millions of comets," says lead author Sujoy Mukhopadhyay, a graduate student at Caltech. "In addition, figuring out the duration of the extinction event and how long it took life to recover has been a difficult problem."

To address both questions, Mukhopadhyay and his colleagues measured the amount of cosmic dust in the sediments of an ancient sea bed which is now exposed on land about 100 miles north of Rome. In particular they focused on a two-centimeter-thick clay deposit that previously had been dated to about 65 million years ago. The base of this clay deposit corresponds to the date of the extinction event.

The clay deposit lies above a layer of limestone sediments, which are essentially the skeletons of microscopic sea life that settled at the bottom of the ancient sea. The limestone deposit also contains a certain percentage of clay particles, which result from erosion on the continents. Finally, mixed in the sediments is extraterrestrial dust that landed in Earth's oceans and then settled out. This dust carries a high concentration of helium-3 (3He), a rare isotope of helium that is depleted on Earth but highly enriched in cosmic matter.

The lower limestone layer abruptly ends at roughly 65 million years, since the organisms in the ocean were suddenly wiped out by the impact event. Thus, the layer immediately above the limestone contains nothing but the clay deposits and extraterrestrial dust that continued to settle at the bottom of the ancient sea. Immediately above the two-centimeter clay deposit is another layer of limestone deposits from microorganisms of the sea that eventually rebounded after the catastrophe.

In this study, the researchers measured the amount of 3He in the sediments to learn about the K-T extinction. They reasoned that a gigantic impact would not change the amount of 3He in the clay deposit. This is because large impacting bodies are mostly vaporized upon impact and release all their helium into the atmosphere. Because helium is a light element, it is not bound to Earth and tends to drift away into space. Therefore, even if a huge amount were brought to Earth by a large impact, the 3He would soon disappear and not show up in the sedimentary layers.

In contrast, 3He brought to Earth by extraterrestrial dust tends to stay trapped in the dust and not be lost to space, says Kenneth Farley, professor of geochemistry at Caltech and coauthor of the paper. So 3He found in the limestone and the clay deposits came from space in the form of dust.

Based on the 3He record obtained from the limestones, the researchers eliminated the possibility that a string of comets had caused the K-T extinctions. Comets are inherently dusty, so a string of them hitting Earth would have brought along a huge amount of new dust, thereby increasing the amount of 3He in the lower limestone deposit.

But the Italian sediment showed a steady concentration of 3He until the time of the impact, eliminating the possibility of a comet swarm. In fact, the researchers found no evidence for periodic comet showers, which have been suggested as the cause of mass extinction events on Earth.

Mukhopadhyay and his colleagues reason that because the "rain-rate" of the extraterrestrial dust from space did not change across the K-T boundary, the 3He concentration in the clay is proportional to the total depositional time of the clay. "It's been difficult to measure the time it took for this two-centimeter clay layer to be deposited," says Farley.

The researchers conclude that the two-centimeter clay layer was deposited in approximately 10,000 years. Then, very quickly, the tiny creatures that create limestone deposits reemerged and again began leaving their corpses on the ocean bed. The implication is that life can get started again very quickly, Farley says.

Thus the study answers two major questions about the event that led to the extinction of the dinosaurs, says Mukhopadhyay. In addition to Mukhopadhyay and Farley, the paper is also authored by Alessandro Montanari of the Geological Observatory in Apiro, Italy.

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Stevenson Receives Feynman Prize for Excellence in Teaching

PASADENA, Ca.— "One hopes that students are being taught to think and not just grind through lots of homework," says Caltech's David Stevenson about the importance of teaching. In recognition of his passion for undergraduate education, Stevenson has been awarded this year's Richard P. Feynman Prize for Excellence in Teaching.

The George Van Osdol Professor of Planetary Sciences, Stevenson was honored by a selection committee composed of faculty and students for modifying the existing Geology 1 class into a new elective course within the core curriculum. "I was challenged," says Stevenson, "by the difficulty of constructing a course that would be attractive to a wide range of students, yet not be too conventional–not just a set of lectures. In practice, it's hard to avoid routine approaches; you want students to learn to think, which means that the problems in the exams, homework, and projects should not be merely routine applications of standard book work." The selection committee cited Stevenson's success in avoiding such routine, noting the increase in the class's enrollment, from 20 students at its start to 165 this year.

The Feynman Prize is made possible by the generosity of an endowment from Ione and Robert E. Paradise, along with additional contributions from Mr. and Mrs. William H. Hurt. It is named in honor of the late Caltech Nobel Laureate and popular science author, who was lauded for his innovative classroom lectures on physics. The prize is given each year to a Caltech professor who demonstrates exceptional ability, creativity, and innovation in both laboratory and classroom instruction.

The selection committee cited Stevenson's "lucid and enthusiastic" teaching style, along with his ability to bring together concepts from evolution, biology, and chemistry, thus making Geology 1 "unlike any other course of its kind in the world." Stevenson also incorporated the use of small group projects, each led by an individual professor, along with field trips to give students the opportunity of first-hand observation. The result, the committee noted, was to create "a lasting impression of how geology research is done, how our Earth was created, and how our environment evolves."

Stevenson notes that teaching is also helpful to him. "Teaching helps the teacher as well as the student. This is especially true of people who are more theoretically inclined in their research"—(Stevenson doesn't have a lab)—"because that kind of research is helped by looking at things with a fresh approach."

He admits, too, that teaching can also be fun: "You can think of different applications of the ideas, how it relates to current research, and how it can be valuable to a non-expert."

Stevenson's own research efforts concerning the origin, evolution, and structure of planets, including Earth, are noteworthy as well. In 1998, the American Geophysical Union awarded him its Harry H. Hess Medal for outstanding achievements in the research of the constitution and evolution of Earth and its sister planets. In addition, in 1993 Stevenson was elected as a Fellow of the Royal Society, the United Kingdom's national academy of science, in recognition of his scientific excellence and work of distinction.

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New planets still being createdIn our stellar neighborhood, study shows

In a study that strengthens the likelihood that solar systems like our own are still being formed, an international team of scientists is reporting today that three young stars in the sun's neighborhood have the raw materials necessary for the formation of Jupiter-sized planets.

Data obtained from the European Space Agency's Infrared Space Observatory (ISO) indicate for the first time that molecular hydrogen is present in the debris disks around young nearby stars. The results are important because experts have long thought that primordial hydrogen—the central building block of gas giants such as Jupiter and Saturn—is no longer present in sufficient quantities in the sun's stellar vicinity to form new planets.

The paper appears in the January 4 issue of the journal Nature.

"We looked at only three stars, but the results could indicate that it's easier to make Jupiter-sized planets than previously thought," said Geoffrey Blake, professor of cosmochemistry at the California Institute of Technology and corresponding author of the study. "There are over 100 candidate debris disks within about 200 light-years of the sun, and our work suggests that many of these systems may still be capable of making planets."

The abundance of Jupiter-sized planets is good news, though indirectly, in the search for extraterrestrial life. A gas giant such as Jupiter, may not be particularly hospitable for the formation of life, but experts think the mere presence of such huge bodies in the outer reaches of a solar system protects smaller rocky planets like Earth from catastrophic comet and meteor impacts. A Jupiter-sized planet possesses a gravitational field sufficient to kick primordial debris into the farthest reaches of the solar system, as Jupiter has presumably done by sending perhaps billions of comets into the Oort Cloud beyond the orbit of Pluto and safely away from Earth.

If comets and meteors were not ejected by gas giants, Blake said, life on Earth and any other Earth-like planets in the universe could periodically be "sterilized" by impacts.

"A comet the size of Hale-Bopp, for example, would vaporize much of Earth's oceans if it hit there," Blake said. "The impact from a 500 km object (about ten times the size of Hale-Bopp) could create nearly 100 atmospheres of rock vapor, the heat from which can evaporate all of the Earth's oceans."

The researchers did not directly detect any planets in the study, but nonetheless found that molecular hydrogen was abundant in all three disks they targeted. In the disk surrounding Beta Pictoris, a Southern Hemisphere star that formed about 20 million years ago approximately 60 light-years from Earth, the team found evidence that hydrogen is present in a quantity at least one-fifth the mass of Jupiter, or about four Neptune's worth of material.

The debris disk of the star 49 Ceti, which is visible near the celestial equator in the constellation Cetus, was found to contain hydrogen in a quantity at least 40 percent of the mass of Jupiter. Saturn's mass is just under a third that of Jupiter. 49 Ceti, which is about 10 million years old, is about 200 light-years from Earth.

Best of all was a 10-million-year-old Southern Hemisphere star about 260 light-years away that goes by the rather unpoetic name HD135344. That star's surrounding debris disk was found to contain the equivalent of at least six Jupiter masses of molecular hydrogen.

"There may not be enough material to form Jupiters around Beta Pictoris or 49 Ceti, but our figures establish a lower limit that is well within the gas-giant planet range, which means we definitely detected a fair amount of gas. And there could be more," Blake said. "Around HD135344, there's at least enough material to make six Jupiters."

Not only does the study reveal that there is still sufficient molecular hydrogen to make gas giants but also that planetary formation is not limited to a narrow time frame in the early history of a star, as previously thought. Because molecular hydrogen is quite difficult to detect from ground-based observatories, experts have relied on measurements of the more easily detectable carbon monoxide (CO) to model the gas dynamics of developing solar systems.

But because results showed that CO tends to dissipate quite rapidly in the early history of debris disks, researchers assumed that molecular hydrogen was likewise absent. Further, the presumed lack of hydrogen limited the time that Jupiter-sized planets could form. However, the new study, coupled with recent theoretical models, shows that CO is not a particularly good tracer of the total gas mass surrounding a new star.

Blake said the study opens new doors to the understanding of planetary growth processes around sun-like stars. He and his colleagues anticipate further progress when the Space Infrared Telescope Facility (SIRTF) and the Stratospheric Observatory for Infrared Astronomy (SOFIA) are launched in 2002. SIRTF, which will have its science headquarters at Caltech, alone could detect literally hundreds of stars that still contain enough primordial hydrogen in their debris disks to form Jupiter-sized planets.

The other authors of the paper are professor of astronomy Ewine F. van Dishoeck and Wing-Fai Thi (the study's lead author), both of the Leiden University in the Netherlands; Jochen Horn and professor Eric Becklin, both of the UCLA Department of Physics and Astronomy; Anneila Sargent, professor of astronomy at Caltech; Mario van den Ancker of the Harvard-Smithsonian Center for Astrophysics; and Antonella Natta of the Osservatorio Astrofisico di Arcetri in Firenze, Italy.

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New results on Martian meteorite support hypothesisthat life can jump between planets

According to one version of the "panspermia" theory, life on Earth could originally have arrived here by way of meteorites from Mars, where conditions early in the history of the solar system are thought to have been more favorable for the creation of life from nonliving ingredients. The only problem has been how a meteorite could get blasted off of Mars without frying any microbial life hitching a ride.

But new research on the celebrated Martian meteorite ALH84001 shows that the rock never got hotter than 105 degrees Fahrenheit during its journey from the Red Planet to Earth, even during the impact that ejected it from Mars, or while plunging through Earth's atmosphere before landing on Antarctic ice thousands of years ago.

In the October 27 issue of the journal Science, Caltech graduate student Benjamin Weiss, undergraduate student Francis Macdonald, geobiology professor Joseph Kirschvink, and their collaborators at Vanderbilt and McGill universities explain results they obtained when testing several thin slices of the meteorite with a new state-of-the-art device known as an Ultra-High Resolution Scanning Superconducting Quantum Interference Device Microscope (UHRSSM). The machine, developed by Franz Baudenbacher and other researchers at Vanderbilt, is designed to detect microscopic differences in the orientation of magnetic lines in rock samples, with a sensitivity up to 10,000 times greater than existing machines.

"What's exciting about this study is that it shows the Martian meteorite made it from the surface of Mars to the surface of Earth without ever getting hot enough to destroy bacteria, or even plant seeds or fungi," says Weiss, the lead author of the Science paper. "Other studies have suggested that rocks can make it from Mars to Earth in a year, and that some living organisms can live in space for several years. So the transfer of life is quite feasible."

The meteorite ALH84001 has been the focus of numerous scientific studies in the last few years because some scientists think there is tantalizing evidence of fossilized life within the rock. The issue has never been conclusively resolved, but Weiss says the matter is not important to the present result.

"In fact, we don't think that this particular meteorite brought life here," says Weiss. "But computer simulations of ejected Martian meteorites demonstrate that about one billion tons of rocks have been brought to Earth from Mars since the two planets formed." Many of these rocks make the transit in less than one year, although ALH84001 took about 15 million years.

"The fact that at least one out of the 16 known Martian rocks made it here without heating tells us that this must be a fairly common process," says Kirschvink.

The sample the Kirschvink team worked with is about 1 mm thick and 2 cm in length and somewhat resembles the African continent, with one side containing a portion of the original surface of the meteorite. Using the UHRSSM, the team found that the sample has a highly aligned and intense magnetic field near the surface, which is to be expected because the surface reached a high temperature when it entered Earth's atmosphere.

The reason this is important is that any weakly magnetized rock will reorient its magnetization to be aligned with the local field direction after it has been heated to high temperatures and cooled. This critical temperature for any magnetic material is known as the blocking temperature. Thus, the outer surface layer of meteorite ALH84001 reached a high temperature well above the blocking temperatures of its magnetic materials, which caused the materials at the surface to realign with Earth's magnetic field.

However, the interior portions of the slice were found to have randomly oriented magnetization, which means that some of the materials inside the meteorite never reached their blocking temperatures since sometime before they left the Martian surface. Further, when the researchers gently heated another slice taken from the interior of the meteorite, they discovered that the interior of the rock started to demagnetize at temperatures as low as 40 degrees Celsius—or 105 degrees Fahrenheit—thus demonstrating that it had never been heated even to that level.

Thus, a radiation-resistant organism able to survive without energy and water for a year could have made the journey from Mars to Earth. Examples of such hardy organisms, like the bacteria bacillus subtilis and deinococcus radiodurans, are already well known.

"Realistically, we don't think any life forms more complicated than single-celled bacterial spores, very tough fungal spores, or well-protected seeds could have made it," Kirschvink says. "They would also have had to go into some kind of dormant stage."

Though the study does not directly address the issue of life in meteorites, the authors say the results eliminate a major objection to the panspermia theory—that any life form reaching Earth by meteorite would have been heat-sterilized during the violent ejection of the rock from its parent planet, or entry into the atmosphere. Prior studies have already shown that a meteorite can enter Earth's atmosphere without its inner material becoming hot.

"ALH 84001 has stimulated a remarkable amount of research to test the hypothesis that life exists elsewhere than on Earth. The present study indicates that the temperature inside the meteorite could have allowed life to persist and possibly travel to Earth from Mars," says Nobel Prize-winning biologist Baruch Blumberg, who is director of NASA's Astrobiology Institute.

The results also demonstrate that critical information could be lost if rocks brought back from Mars by a sample return mission were heat-sterilized, as has been proposed. Thermal sterilization would destroy valuable magnetic, biological, and petrological information contained in the samples.

If life ever evolved on Mars, it is likely to have jumped repeatedly to Earth over geological times. Because the reverse process—the transfer of Earth life to Mars—is dynamically much more difficult, it may be more important to instead protect any Martian biosphere from Earthly microbes.

According to Kirschvink, "The Martian biosphere, if it ever evolved, would most likely have been brought to Earth billions of years ago, and could have participated in the evolution and diversification of bacterial life here.

"So there is at least a chance that we are in part descended from Martian microbes," Kirschvink says.

The ALH84001 research was funded in part by NASA's Astrobiology Institute, an international research consortium involving academic, non-profit and NASA field centers, whose central administrative office is located at NASA's Ames Research Center in California's Silicon Valley. A group from the Jet Propulsion Laboratory in Pasadena, CA, which sponsored the Caltech research, is one of the 11 lead teams of the institute.

Contact: Robert Tindol (626) 395-3631

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