Martian ice age. Somewhere between 400,000 and 2.1 million years ago, very recent history in geological terms, Mars was immersed in an ice age similar in many ways to those that have occurred on Earth. The discovery of periodic ice ages on Mars was recently made by a team of scientists that includes David Marchant, a CAS associate professor of earth sciences, and colleagues at Brown University and the Kharkov National University in the Ukraine.

Using information from NASA’s Mars Global Surveyor and Odyssey missions, the researchers examined global patterns of landscape shapes and near-surface water ice mapped by the orbiting satellites. Drawing upon Marchant’s expertise, accumulated in more than 17 field seasons analyzing ice and landforms in the Antarctic Dry Valleys -- whose environment is markedly similar to the Martian landscape -- they were able to predict where ice might occur on Mars and correlate satellite images with landforms characteristic of buried ice. These formations were found at latitudes as far south as 30 degrees, the equivalent of New Orleans, Shanghai, or New Delhi.

The researchers also connected changes in Mars’ landscape with variations in the planet’s orbit and tilt, factors that are also important in variations in Earth’s climate.

According to James Head, a planetary scientist at Brown University and lead author of the study, “Of all the solar system planets, Mars has the climate most like that of Earth. Both are sensitive to small changes in orbital parameters. Now we’re seeing that Mars, like Earth, is in a period between ice ages.”

Interestingly, the researchers found that in contrast to the process on Earth, a Martian ice age begins as the poles warm up and water vapor is transported toward lower latitudes, where it is deposited as frost or snow mixed with dust. It recedes when the poles cool and lock water into the polar ice caps. On Earth, however, ice ages are marked by polar cooling, where ocean water freezes into ice sheets.

The Mars work was published in the December 18 issue of the journal Nature.

Of form and function. Much of the world we know, from jumbo jets to computer chips, is made of polycrystals -- materials that combine two or more crystalline elements. Since crystals have a regularly repeating internal arrangement of atoms, when two such elements combine they form predictable patterns, or textures.

Traditionally, three types of textures have been identified: random, fiber, and epitaxy. Each contributes particular electrical, magnetic, and mechanical qualities to the materials it comprises.

Ahmet Özcan (GRS’03), a research associate working with CAS Physics Professor Karl Ludwig and associates at IBM, has uncovered a new kind of texture, which has been dubbed “axiotaxy.” The new texture was observed in silicides, materials used as contacts between metals and semiconductors in integrated circuits, the technology basic to modern computing and communication.

The researchers used a technique called X-ray diffraction, which reveals the polycrystal structure as a circular pattern called a pole figure. Rather than the concentric circles or well-defined spots characteristic of traditional textures, they observed a complex pattern of lines and spots similar to what might be seen in a kaleidoscope.

According to Özcan, while observing a new texture type is in itself a valuable contribution to the field of materials science, understanding the unique mechanisms that cause this new type of texture is equally important and will help illuminate the physics of thin film growth and transformation. A clear understanding of the underlying structure of polycrystalline materials and how they change over time is vital to meet the continuing demand for miniaturization of computers, cell phones, and other silicon-based devices.