Erika Gibb

Erika Gibb, a professor of physics and astronomy at the University of Missouri–St. Louis, and Mohi Saki, graduate research assistant, co-authored a W.M. Keck Observatory study, which found that Comet 46P/Wirtanen released an abnormally high amount of alcohol as flew past earth in 2018. Gibb and her co-authors also identified a mystery heat source in the comet. (Photo by August Jennewein)

When Comet 46P/Wirtanen, also known as the “Christmas Comet,” passed Earth in December 2018, it was flying under the influence according to a new study from the W.M. Keck Observatory.

Erika Gibb, a professor of physics and astronomy at the University of Missouri–St. Louis, and Mohi Saki, graduate research assistant, co-authored the study, which found that the comet released an abnormally high amount of alcohol as is flew within 7.1 million miles of Earth more than two years ago.

The Planetary Science Journal published the findings in March. Since then, the study has been cited by NASA and featured in numerous national and international media outlets including The Daily Mail, Florida News Times, IFL Science, The Science Times, Smithsonian Magazine and Universe Today.

NASA awarded Gibb and her fellow researchers time to observe Wirtanen using Keck Observatory’s Near-Infrared Spectrograph (NIRSPEC) in 2018 just as the comet was approaching earth. Data from the NIRSPEC showed its chemical makeup consisted of acetylene, ammonia, ethane, formaldehyde, hydrogen cyanide, methanol and water.

Saki noted that researchers obtained measurements of the abundances and spatial distributions of the comet’s chemical building blocks with just 20 minutes of observation with the NIRSPEC. He added that the same level of detail would take hours with other instruments.

Comet trails often contain methanol, a non-potable alcohol, but other molecules typically exceed the amount of alcohol preset. The researchers think the makeup of Wirtanen could lead to further insights about the origins of the solar system.

“46P/Wirtanen has one of the highest alcohol-to-aldehyde ratios measured in any comet to date,” said Neil Dello Russo, cometary scientist at Johns Hopkins University Applied Physics Laboratory and co-author of the study, in a statement. “This tells us information about how carbon, oxygen, and hydrogen molecules were distributed in the early solar system where Wirtanen formed.”

In addition to the high level of alcohol expelled by Wirtanen, Gibb and her colleagues also identified a mystery heat source.

When a comet orbits close to the sun, frozen particles in the nucleus heat up and transition from a solid directly to gas. This process produces the coma – a nebulous layer of gas and dust that glows around the nucleus. Solar radiation from the sun then pushes some of the coma away from the nucleus, creating the iconic comet tail.

However, Gibb found something besides solar radiation at work.

“Interestingly, we found that the temperature measured for water gas in the coma did not decrease significantly with distance from the nucleus, which implies a heating mechanism,” she said.

She posited that is could be a chemical reaction, causing the release of high-velocity electrons that transfer kinetic energy to heat the water and gas in the coma.

“Another possibility is there may be solid chunks of ice flying off of 46P/Wirtanen,” Gibb said. “We’ve seen this in some comets visited by spacecraft, notably Hartley 2 during NASA’s EPOXI mission. Those ice chunks tumble away from the nucleus and sublimate, releasing energy further out in the coma.”

Gibb and her co-authors are continuing to examine the data. The molecules they focused on have never been studied in Wirtanen, and their research could determine if a spacecraft mission to engage in follow-up observations is appropriate in the future.

Media coverage:
The Daily Mail
Florida News Times 
IFL Science
The Science Times
Smithsonian Magazine
Space Daily
Universe Today

Burk Krohe

Burk Krohe