Departments
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Week of 25 September 1998 |
Vol. II, No. 7 |
Feature
Article
Think globally, act universally
Expert on atmospheres of planets and moons to give 54th University Lecture
By Eric McHenry
For the title of his 1998/99 University Lecture, Michael Mendillo has chosen a biblical allusion -- Astronomy Through a Glass, Darkly -- that seems to place emphasis on what isn't known about his subject. That's no accident, he says; our understanding of astronomy, like the sky into which we stare, is faint in several places.
Mendillo, CAS professor of astronomy and ENG professor of electrical engineering, has with BU colleagues spent the past four years confirming that the moon's atmosphere is approximately twice as large as it was previously thought to be, and has contributed to a similarly fundamental discovery about the tails of comets. "This field is really still in its infancy," Mendillo says of his lecture's subtitle, Searching for Extended Atmospheres of Planets, Moons, and Comets.
Moreover, the BU astronomers have made their observations using an imaging system with a special filter developed by Senior Research Associate Jeffrey Baumgardner. This permits only light of a certain color to enter their telescope -- literally, "through a glass, darkly."
"We're rejecting most of the light," Mendillo says, "when looking at something that's very faint. But this allows us to see things that we can't see in the fullness of white light."
Elucidating such specialized research for an audience of nonspecialists, Mendillo observes, is a challenge more scientists need to face. He will draw, in his lecture, upon a quarter-century of experience teaching both introductory- and advanced-level courses.
"Most of my teaching is to nonscience majors," he says, "so I've spent a lot of time learning to deliver science to a nontechnical audience.
"The difference," he adds with a chuckle, "is I've always had a semester; this time I only have 50 minutes."
One of the ways Mendillo makes his material accessible is by talking about its real-world (real-solar system, in this case) application. What he and his associates learn about lunar atmospheres will be of continuing use to space explorers: their study of Jupiter's moons, the earth's moon, and comets is partially supported by NASA, a self-described "mission-oriented agency." Some of the funding NASA has provided is earmarked for research that will assist missions already in the works. Other grants are meant for basic research that lays the groundwork for future expeditions.
"Take the Jupiter work," he says. "There's currently a very big NASA satellite out there called Galileo, and it will probably only be operable for another year or two because the high-radiation environment is damaging it. But it's taking wonderful data. So all of our observations of Jupiter's large sodium nebula are made with the full coordination and support of the Galileo mission. We make ground-based observations to provide NASA with a context, an understanding of the region where their satellite is whizzing around making its measurements. That's very mission-oriented.
"Our studies of the earth's moon," he says, "are more on the basic-research side of NASA. There will be missions to near-earth asteroids coming up, and those are very primitive bodies -- bodies that have been in the solar system, unchanged, for a long, long time. The moon is also a primitive body, and studying it gives us a useful basis for comparison."
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Michael Mendillo
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"I think Hale-Bopp created a lot of comet scientists," says Jody Wilson, a post-doctoral research associate who, at Mendillo's suggestion, trained his telescope on the comet while conducting lunar studies at the McDonald Observatory in southwest Texas.
"A lot of people," says Wilson, "who wouldn't have considered studying comets before experienced the same thing I did. They said, 'Hey, there's Hale-Bopp. The object we're looking at is below the horizon now; let's take a look at the comet.'"
Because Wilson was gazing through a small, wide-angle telescope that enabled him to see all of Hale-Bopp, and because that telescope was fitted with a special filter for detecting sodium-based light, the images he captured reveal a never-before-observed sodium tail. A European research contingent also saw the tail, but recorded images that say very different things about its shape and character. Together, the two groups have added considerably to what is known about comets.
"The tail that the European team saw was very narrow and pointed almost exactly away from the sun," says Wilson. "So the sodium in that tail has to be coming right from the comet's nucleus -- that little ball of ice that produces all of the tails. In our images, the sodium appears to be coming from dust grains in the comet's dust tail. That's neat because it's an analogue to the moon: sodium atoms in the lunar atmosphere are coming from broken-up soil on the moon's surface."
The moon, in turn, is a useful analogue for our own celestial body. Mendillo says that another of the themes he continually sounds in his teaching is the applicability of atmospheric science to the study of life on earth. Visiting that idea, he says, will help him keep his University Lecture on what is, for the audience, familiar terrain.
"This is fundamentally interesting material," he says, "because it relates to the great questions we have, as humans. We want to understand our place in the universe at any number of levels -- philosophical, religious, scientific. Now I can only help out on the scientific end of things. To understand our place in the physical universe, it's worthwhile to think about our neighborhood -- the moons, the planets, the comets -- and to see how they all formed and evolved. Only by doing so do we realize how special the earth is.
"Some of the celestial bodies in our neighborhood are quite similar to one another, but the earth is unique," he says. "And we're on it. Maybe we ought to acknowledge that and take a little better care of it."
The annual University Lecture, now in its 54th year, will take place at 7:30 p.m. Monday, October 5, in the Tsai Performance Center, 685 Commonwealth Ave. It is free and open to the public.