Comet that recently buzzed Earth was unlike any ever seen before

6 Dec 2017

Image: Triff/Shutterstock

The recent flyby of comet 45P gave astronomers an unprecedented view of a truly strange chunk of space debris.

Comets and other space debris often whizz past Earth. While some might come too close for comfort, the recent flyby of Comet 45P/Honda-Mrkos-Pajdušáková was a much-welcomed rarity.

When it flew past at its closest point of 12.3 million km from Earth, astronomers from across the globe trained their powerful telescopes on the object, including NASA’s Infrared Telescope Facility (IRTF) in Hawaii.

In a paper published to the The Astronomical Journal, a research team revealed it had measured the levels of nine gases released from the icy nucleus into the comet’s thin atmosphere (coma).

Several of these gases are crucial to the formation of amino acids, sugars and other factors often attributed to the emergence of life. Of particular interest were carbon monoxide and methane, which are hard to detect in Jupiter-family comets and have only been studied a few times before.

These Jupiter comets frequent the orbital loop of the planet around the sun every five to seven years, but much less is known about native ices in this group than in the long-haul comets from the Oort cloud.

Comet 45p

Comet 45P captured on 22 December using a telescope from Farm Tivoli in Namibia, Africa. Image: Gerald Rhemann

A true space oddity

During January of this year, the IRTF analysis of 45P revealed that the comet is almost completely depleted of carbon monoxide.

This wasn’t so much of a surprise for the researchers because this depletion occurs as the comet is heated up by the sun, but what was perplexing was that 45P should, by this reality, also have very little methane. However, analysis shows it is rich in methane, making it a considerable rarity in the grander scheme of the universe.

While it is possible that the methane got trapped inside other ice in the comet, the likelier outcome is that it reacted with hydrogen to form methanol.

When exactly this reaction took place is a mystery – either the comet had always been this way, or the levels of carbon monoxide and methanol in the coma might have changed over time.

This makes Comet 45P both an oddity to science and one that simply doesn’t match any comet studied so far.

“This research is groundbreaking,” said Faith Vilas, who helped support the study.

“This broadens our knowledge of the mix of molecular species coexisting in the nuclei of Jovian-family comets, and the differences that exist after many trips around the sun.”

The team will now will analyse a further four comets that followed 45P, with 21P/Giacobini-Zinner and 46P/Wirtanen expected to remain within 16 million km of Earth throughout most of December 2018.

Colm Gorey was a senior journalist with Silicon Republic