From Earth to Mars: Structure of CO2 Crystals Helps Interplanetary Studies

Discoveries by Agricultural Research Service scientists may affect future Mars missions to study the Red Planet's polar ice caps.

Cytologist William P. Wergin and botanist Eric F. Erbe at ARS' Nematology Laboratory in Beltsville, Md., developed the first technique for viewing and photographing carbon dioxide crystals using a scanning electron microscope or SEM. SEM images are formed by electrons that pass through a magnetic field. The field serves as a "lens." The images can be displayed on a cathode ray tube similar to a TV screen and recorded.

Frozen CO2 makes up most of the Martian polar ice caps. Earth and Mars are the only two planets in our solar system with polar ice caps that expand and contract in response to changing seasons. These facts have made the Beltsville scientists' research of great interest to their colleagues "next door" in nearby Greenbelt, Md., at Goddard Space Flight Center of the National Aeronautics and Space Administration.

ARS and NASA scientists are cooperating to adapt SEM technology to studies of the Martian surface. Goddard collaborators include climatologist James L. Foster, physicist Al T. C. Chang and hydrologist Dorothy K. Hall at NASA's Laboratory of Hydrospheric Processes, and geologist J. Barton of General Sciences Corp.

NASA scientists say SEM technology, together with modeling studies and experiments using microwave radiometers, may enable them to assess for the first time the thickness of the seasonal Martian ice caps. On Mars, as on Earth, ice plays an important role in large-scale climate processes.

ARS is the research arm of the U.S. Department of Agriculture. A story about the SEM project appears in the October issue of ARS' Agricultural Research magazine. The story also is online at:

http://www.ars.usda.gov/is/AR/archive/oct98/crys1098.htm

Scientific contact: William P. Wergin, ARS Nematology Laboratory, Beltsville Agricultural Research Center, Beltsville, Md., (301) 504-9027, fax (301) 504-8923, wwergin@ggpl.arsusda.gov.