Dec. 11, 2006
Don Gurnett To Deliver Franklin Lecture At AGU Fall Meeting In San Francisco
The legacy of American statesman, author and scientist Benjamin Franklin will be revisited when University of Iowa space physicist Don Gurnett delivers the prestigious Franklin Lecture at the American Geophysical Union (AGU) fall meeting Dec. 11-15 in San Francisco.
The lecture, titled "Lightning in Planetary Atmospheres," is the second in the AGU series focused on current science in lightning-related fields of research and is named for Benjamin Franklin, who famously demonstrated that lightning is an electrical phenomenon in part by flying a kite during an electrical storm.
In his talk, Gurnett plans to speak on lightning in planetary atmospheres, as detected by spacecraft-borne imaging, high-frequency radio, and low-frequency plasma wave instruments. Using these techniques, says Gurnett, lightning has been reported at five planets other than Earth: Venus, Jupiter, Saturn, Uranus, and Neptune. Of these, the existence of lightning at Venus is controversial, and the evidence of lightning at Neptune is at best marginal. Jupiter and Saturn have by far the most intense and well-documented lightning activity.
Gurnett points out that lightning remains as interesting to modern day scientists as it was in Franklin's day. In 1953, Nobel Prize winning chemist Harold Urey (1893-1981) and graduate student Stanley Miller took lightning into account when they conducted one of the classic experiments on how the building blocks of life may have originated from Earth's constituent gases. After placing water, methane, ammonia and hydrogen in a closed system of glass tubes and flasks, they heated the mixture to get it into gaseous form, then fired sparks between two electrodes to simulate lightning. They found that some of the carbon formed amino acids, including many of the amino acids used to make proteins in living cells.
Lightning also presents a great risk to life. Gurnett notes that it accounts for about 200 fatalities per year, among the most of any weather-related phenomenon. Lightning is also of great concern to NASA, as it presents a great risk for rockets poised for launch into space from the Kennedy Space Center at Cape Canaveral, Fla. And lightning will be of concern to astronauts preparing to journey to Mars, which periodically has huge dust storms. At the Earth, lightning and other electrical phenomena are known to occur in dust storms; presumably, similar phenomena take place at Mars.
Concerning lightning at the "gas giant" planets, Gurnett says, "The available data shows that the lightning discharges at Jupiter, Saturn, Uranus, and maybe Neptune, are much more intense than terrestrial lightning, by factors of 10 to 10,000, depending on the method of comparison. Since the electrical breakdown field increases with pressure, the high intensities suggest that lightning at the giant planets, and the convective storms that cause the discharges, occur deep in the atmosphere, at pressures considerably greater than for terrestrial lightning. It is believed that water vapor is crucial to the production of lightning."
A UI faculty member in the UI College of Liberal Arts and Sciences Department of Physics and Astronomy since 1965, Gurnett earned his bachelor's degree in electrical engineering from the UI College of Engineering and his master's degree and doctorate from the UI Department of Physics and Astronomy under the direction of Dr. James A. Van Allen. His early discoveries and investigations included observations of intense radio emissions from the Earth's aurora. He used data from UI-built Voyager instruments to make the first observations of plasma waves and low-frequency radio emissions in the magnetospheres of Jupiter, Saturn, Uranus and Neptune and discovered lightning in the atmospheres of Jupiter and Neptune.
He currently has instruments aboard NASA's Cassini spacecraft -- presently midway through a four-year exploration of Saturn and its moons -- and the European Space Agency's Mars Express spacecraft, which is searching for underground water at Mars. He has been studying lightning storms at Saturn with instrument on Cassini. Gurnett adds that he also plans to search for lightning at Mars starting in January. Mars has large seasonal dust storms that are expected to start early next year, and he hopes to find out if these storms produce electrical activity.
Gurnett has participated as a principal investigator or co-investigator on more than 30 major spacecraft projects, including the Voyager 1 and Voyager 2 flights to the outer planets, the Galileo mission to Jupiter, and the Cassini mission to Saturn. The author or co-author of more than 320 scientific publications, he is a member of the International Scientific Radio Union (URSI), a Fellow of the American Geophysical Union, a Fellow of the American Physical Society, a Fellow of the American Academy of Sciences and a member of the Iowa Academy of Science (IAS). He was elected to membership in the prestigious National Academy of Sciences (NAS) in 1998.
STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Suite 371, Iowa City, Iowa 52242-2500.
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