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[Sandia Lab News]

Vol. 54, No. 12        June 14, 2002
[Sandia National Laboratories]

Albuquerque, New Mexico 87185-0165    ||   Livermore, California 94550-0969
Tonopah, Nevada; Nevada Test Site; Amarillo, Texas

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Rings around the Earth? EUVL tool ordered Sandians comment on Mars water discovery



Rings around the Earth: A clue to climate change?

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By Will Keener

Rings around the Earth?

While most of us know about rings around Saturn and Jupiter, some scientists believe there have been rings of rock debris around our own planet. Two scientists -- Peter Fawcett of the University of New Mexico and Sandia's Mark Boslough (9212) -- have suggested that a geologically "recent" collision (about 35 million years ago) may have caused such a temporary debris ring.

The two also suggest that such temporary rings -- lasting from 100,000 to a few millions of years -- may explain some patterns of climate change observed in the Earth's geological record. These conclusions are spelled out in an upcoming article in the Journal of Geophysical Research, Atmospheres.

Lore of the Rings

"One way to get a ring," says Mark, "is with an impact." There is a growing body of evidence showing that the Earth has been subjected to numerous impacts by comets and asteroids throughout its history. Among these impacts are Meteor Crater in Arizona, the buried Chixulub crater in the Yucatan Peninsula of Mexico, and a chain of at least five craters spread across several continents.

Several studies, both theoretical and with laboratory data, suggest that some large impacts are capable of ejecting material into space in the form of debris rings, if the mechanics of the impact meet certain requirements. The authors conclude that the mostly likely scenario for ring creation is a low-angle impact by a fiery meteor. Some Earth materials and melted meteoric debris, called "tektites," would form the ring materials.

Mark and Peter describe an impact where the meteor ricochets back into the atmosphere. The ricochet becomes part of an expanding vapor cloud, setting up an interaction that allows some of the debris to attain orbit velocity. The orbiting debris will collapse into a single plane by the same mechanics that led to the rings of Saturn and other planets, Mark explains. Such a ring would most likely form near the equator, because of the dynamics involved with the moon and the Earth's equatorial bulge.

Speculation on climates past

The effects of the larger impact events on Earth's environment and climate have been the subjects of much speculation and research over the past two decades. "Clearly, large impacts have affected the evolution of the Earth, life on it, and its atmospheric environment," says Peter, who teaches paleoclimatology, mathematical modeling, and environmental science in UNM's Earth and Planetary Sciences Department.

Much of the paleoclimate work has focused on the Cretaceous-Tertiary (K-T) boundary event, which marked a mass extinction and the end of the age of the dinosaurs. A number of these studies suggest an impact resulting in the suspension of a layer of dust in the upper atmosphere, blocking sunlight and cooling the Earth. But could other impacts result in different atmosphere-altering phenomena?

An equatorial ring would cast a shadow primarily in the tropics, as it does for Saturn. (See illustration on page 4.) Depending on location, surface area, and darkness of the ring shadow, the amount of incoming solar warmth, or insolation, could be significantly altered, the two concluded. To test their theory, the two assumed an opaque ring, like Saturn's B-ring, scaled to Earth-size, and tested global climate effects using a climate model.

The model selected and modified for the simulation was developed by the National Center for Atmospheric Research (NCAR). NCAR's "Genesis" climate model includes atmospheric circulation information and layers of vegetation, soil, snow, sea temperature, and land ice data.

"The idea for this project was to write a distributed-memory parallel version of this existing and popular climate code, so we could run it on machines with Cplant-type architectures," Mark explains. "From Sandia's point of view, we wanted to gain experience with the code and develop collaborations with the paleoclimatology research community."

Sandia funded Mark's work on the program through its Laboratory Directed Research and Development (LDRD) program and Peter's efforts through the Sandia University Research Program (SURP). Mark accomplished the rewriting of the code and crunched the ring data. Peter shared his expertise to analyze the results.

Ring World

"The equatorial debris ring has a profound effect on climate, because it reflects a significant fraction of tropical insolation back to space before it can interact with the atmosphere," the pair conclude. Surface and atmospheric temperatures, changes in temperature ranges from equator to poles, circulation patterns, and the rain and snow cycles were all impacted by the ring, their model showed.

The two scientists looked at changes shown in the model to predict changes that might be found in the Earth's geologic record as a way to test their work. In addition to the K-T boundary event, they looked at more recent impacts and a much older one.

The most recent event -- about 35 million years ago -- is identified by an iridium layer (often associated with meteors) and two pronounced micro-tektite fields, where these melted meteor-related materials have been found and dated. Climatic records from sedimentary materials just above the iridium/micro-tektite interval indicate a 100,000-year cooling interval. Orbiting debris in a ring, casting its shadow in the subtropics, could have sustained such a cooling trend, the two authors suggest.

The K-T boundary impact (about 65 million years ago) was much larger than the more recent impact and had a much larger immediate effect on the environment as measured by extinctions and atmospheric changes. But there were no long-term effects on the climate, leading the authors to conclude the event probably did not generate a debris ring.

This large-impact without a ring underscores the importance of the geometry of an Earth collision, Mark explains. When the size of the impacting body is below some critical dimension, the impact must be at a shallow angle to create ring debris. - - Will Keener

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First commercial EUVL tool ordered, VNL user facility on track

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By Nancy Garcia

Just as anticipated five years ago, the founding member of the Extreme Ultraviolet Lithography Limited Liability Corp., Intel, has placed an order for the first beta version of a lithography tool based on technology developed at Sandia through a historic labs-industry partnership.

An unprecedented $250 million Cooperative Research and Development Agreement in 1997 between the Intel-led consortium and the Virtual National Lab -- Sandia, Lawrence Livermore, and Lawrence Berkeley national laboratories -- led last year to integration of the first full-field EUVL chip-patterning tool, the Engineering Test Stand, at Sandia.

"It's no longer just a VNL technology," says Glenn Kubiak, leader of the Nanoscale Science and Engineering Section in Center 8700. "It's becoming a truly commercially available technology, with an order from the world's largest exposure tool manufacturer" (ASML, the tool-making supplier of the order from Intel).

In keeping with this transition from a precompetitive phase of collaborative research with industry, the VNL is poised to begin a technology-maturation phase by offering access to a Resource Development Center (RDC) at the VNL beginning next year.

In the RDC, research agreements are anticipated from integrated circuit manufacturers, the EUV LLC, semiconductor equipment manufacturers such as ASML, and Sematech, the advanced manufacturing and development consortium.

In the past year since the site celebrated completion of the Engineering Test Stand (Lab News, April 6 and April 20, 2001), Glenn says, efforts have focused on making upgrades to enable reliable access to chip companies that will use the tool for process development and learning. Individual companies can practice exposing wafers with circuit patterns using the exposure tool. Equipment manufacturers, meanwhile, will study the tool environment to reduce contamination of the optical system and investigate the EUV light source.

EUV patterning, or lithography, is considered an extension of the current approach to reducing and printing circuit patterns on wafers. However, EUV light is more than 10 times shorter in wavelength, requiring the use of reflective image-reduction surfaces and photomasks, since this wavelength would be absorbed by traditional clear lenses.

This next-generation approach was undertaken because the chip-making industry faced insurmountable physical limits along its path of doubling the number of transistors that can be packed into a chip every 18 months to two years, a pace that has propelled the business for the last 30 years.

Patterning wafers with shorter wavelengths of light allows finer features and thus more densely packed transistors. That translates into better performance, with clock speeds of up to 10 GHz or faster (compared to the best speeds today of 2.4 GHz).

The beta tool ordered by Intel is expected to be delivered in 2005, and the first commercial chip production with EUVL should take place in 2006-2007. ASML anticipates it will be used to image critical layers in integrated circuits with feature sizes below 45 nm. - - John German

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Lockheed Martin, Los Alamos played key roles in discovery of 'vast quantities of water' on Mars

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By Bill Murphy

It is certainly one of the most significant discoveries in the history of planetary exploration. NASA's Jet Propulsion Laboratory announced May 28 that its 2001 Mars Odyssey spacecraft has identified vast quantities of subsurface water on Mars. The water exists in the form of "dirty ice," as one JPL senior scientist described it, and if melted would be enough to fill Lake Michigan twice over. The discovery was based largely on observations of the planet's south polar region. When the northern region's seasonal cover of frozen carbon dioxide melts, scientists expect Odyssey's instruments to reveal even more water in that region of the globe.

The discovery was made using Odyssey's on-board gamma ray spectrometer suite of instruments. A key element of that suite, the mission's neutron spectrometer, was developed at Los Alamos National Laboratory. Lockheed Martin Astronautics in Denver developed and built the Odyssey orbiter and, jointly with the JPL, conducts mission operations.

"We have suspected for some time that Mars once had large amounts of water near the surface," said Jim Garvin, Mars Program Scientist, NASA Headquarters, Washington. "The big questions we are trying to answer are, 'where did all that water go?' and 'what are the implications for life?' Measuring and mapping the icy soils in the polar regions of Mars as the Odyssey team has done is an important piece of this puzzle, but we need to continue searching, perhaps much deeper underground, for what happened to the rest of the water we think Mars once had."

Several Sandia researchers who have closely followed NASA's Mars missions expressed delight and excitement at the latest discovery. They offered some perspectives on what the discovery might mean for future Mars exploration.

Len Duda (2542), an official JPL/NASA "Solar System Ambassador" (see story on page 12), says, "I found the announcement very exciting. It means that the probability for some form of life to have existed on Mars in the past has increased and places a new emphasis for the next Mars Rover mission in 2003. Also, this discovery makes a manned Mars mission easier to accomplish -- you won't need to bring all the water you'll need -- and much more interesting for its exploration possibilities."

Ron Lipinski, Roger Lenard, and Steve Wright, colleagues in Advanced Nuclear Concepts Dept. 6424, have thought long and hard about Mars missions and how nuclear power might play a role.

Says Ron: "My congratulations to the Los Alamos science team. The discovery of substantial quantities of water ice in the upper few feet of Martian soil should provide the scientific impetus to galvanize Mars exploration efforts. The likelihood of finding microbial life there is now much higher. This could spur the deployment of Martian rovers with various microsensors and perhaps even a Mars global rover powered by a small reactor. Numerous analyses and experiments have been conducted to indicate that such a pervasive source of water might also be used for base support and manufacture of return propellant for a human expedition, thus reducing the cost of such a venture. Sandia could play a significant part in providing sensors, radiation-hardened electronics, and power to such future missions.

Adds Roger: "The presence of such water deposits has re-energized the debate over Viking lander biochemistry experiment results [from 1976] -- only expeditions with much more capable sensors and chemical processing suites can resolve the existing issues. Further, greatly enhanced surface mobility is going to be necessary."

Steve brings the issue closer to home, noting that Sandia's expertise in nuclear energy systems might be a critical component of future missions. He says, "Substantial amounts of power are going to be required to process the water for use on Mars, regardless whether it is to be used for the production of oxygen to support human life, production of propellant for the return trip home or for use in mobile vehicles, or for the generation of hydrogen and oxygen in fuel cells. We believe that this finding will increase the growing need for the development of small nuclear power systems on the surface of Mars for the production of power to process water for a variety of uses."

JPL manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington. In addition to Los Alamos and Lockheed Martin, other key mission collaborators include: Arizona State University, the University of Arizona,

NASA's Johnson Space Center in Houston, and the Russian Aviation and Space Agency (which provided the high-energy neutron detector). -- Nancy Garcia

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Last modified: June 14, 2002


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