View from Mars Hill: 30th anniversary of the discovery of comet Shoemaker-Levy-9

KEVIN SCHINDLER

Next week marks the 30th anniversary of the date that Gene and Carolyn Shoemaker began their ascendancy from well-known scientists to world-famous legends. They had long been cemented as leading figures in the field of astrogeology — the geology of celestial bodies in our solar system. But it was their discovery of a comet on the evening of March 24, 1993, that captured the attention of people around the world while giving Gene a life-coming-full-circle experience.

Four decades before their great discovery, Gene and Carolyn Shoemaker were in the early years of their marriage, and Gene was in a similar, nascent stage of his career as a geologist. He studied impact craters around the world, proved the impact origin of Meteor Crater, searched for potential Earth impacting asteroids and comets in the sky, and relocated the United States Geological Survey’s Astrogeology Branch to Flagstaff as a center for preparing the geological exploration of the moon for the Apollo program.

People are also reading…

Meanwhile, Carolyn taught for a short time but found she didn’t really like it. So, when the couple had kids (three), she stayed at home to raise them while Gene worked. And so life went for the Shoemakers until 1980, when all of the children had graduated high school. Now 51 years old, Carolyn looked for something fulfilling on which to spend her time.

Gene was then leading the Palomar Asteroid and Comet Survey, which used the Palomar Observatory’s (in California) 18-inch Schmidt telescope to search for asteroids and comets that might one day impact Earth. This work involved photographing segments of the sky and scanning the resulting films with a stereomicroscope for suspects. Gene suggested that Carolyn join the project and after some training, she began her astronomical career.

For the next 18 years, the Shoemakers worked side-by-side, and often with other scientists, in various efforts to search for comets and asteroids. They represented several research institutions, including the United States Geological Survey’s Astrogeology Branch, California Institute of Technology, Northern Arizona University and Lowell Observatory. This work resulted in the discovery of more than 500 asteroids and 32 comets (for a time, Carolyn would hold the record for most comets discovered by an individual).

In addition to searching the skies for potential Earth impactors, the Shoemakers also scoured Earth — especially Australia — for terrestrial impact structures. By comparing these terrestrial records of impacts with the astronomical searches for potential impactors, the Shoemakers hoped to better understand the nature of impacting throughout the solar system, as well as how impacting had changed over time.

Of all his work, the Shoemaker’s most famous contribution was their comet discovery made on March 24, 1993. Teamed with amateur astronomer David Levy, they went on an observing run at Palomar Observatory searching for potentially Earth-impacting comets and asteroids. While Gene and Levy captured images with the 18-inch Schmidt telescope, Carolyn examined previously developed images through the stereomicroscope.

At about 4 p.m. (the same time, incidentally, that Clyde Tombaugh discovered Pluto on a cold February night 63 years prior), she detected what looked like a comet, but one that was unusual because it looked smashed. It turned out that this was in fact a comet, but one that had fractured. This was the ninth such comet discovered by the Shoemaker-Levy team, and it was thus designated Comet Shoemaker-Levy 9 (SL-9 for short).

Scientists soon realized that the pieces would not impact Earth, but instead were on a collision course with Jupiter! The following July, astronomers around the world watched as 21 different fragments of SL-9 crashed into Jupiter. This provided the first-ever direct observation of the collision of two solar system bodies. What a perfect way for Gene Shoemaker to cap his career; he had spent his life searching for potential comet and asteroid impactors and studying impact sites on Earth, and now could join a world-wide audience in seeing a planetary collision for the first time. And by an impactor that he had discovered.

As a postscript, and in an eerie final act of Gene’s life, he died in an automobile collision in 1997, when he and Carolyn were in Australia studying impact sites. Carolyn was also in the car but survived and lived for another quarter century.

Get opinion pieces, letters and editorials sent directly to your inbox weekly!