Last November, after a decade-long journey, Rosetta’s Philae lander touched down on the surface of comet 67P/Churyumov-Gerasimenko, a regular visitor to our inner solar system.
The little lander bounced a time or two before coming to rest and then proceeded to collect samples from the comet’s surface. After the specimens were analyzed, the results were relayed to earthlings eagerly awaiting word on what Philae had found.
What Philae had discovered was a treasure trove of chemical compounds, including methyl isocyanate, a new cometary molecule. And when Lucy Ziurys and DeWayne Halfen got word of Philae’s findings, Halfen, an assistant astronomer in the Department of Astronomy at the University of Arizona, decided to see if he and Ziurys could locate methyl isocyanate molecules in interstellar space, where it hadn’t been seen before.
Each chemical compound has its own spectral signature, or fingerprint, that depends on variables such as a compound’s geometry, how its atoms are arranged, and the length and angle of its chemical bonds.
"If we know the fingerprint of a given molecule, we can go to a radio telescope and see if that molecule exists in some astronomical object," says Ziurys, a professor of chemistry/biochemistry and astronomy at the UA.
Which is just what she, Halfen and their collaborator, Vadim Ilyushin of the Ukraine’s Institute of Radio Astronomy, did. The researchers used the Arizona Radio Observatory 12-meter telescope on Kitt Peak to look for interstellar methyl isocyanate, or CH3NCO.
"We looked for methyl isocyanate’s spectral signature, and we found it in Sagittarius B2N, a famous molecular cloud in the galactic center," Halfen says.
All solar systems form from these big clouds, which collapse to create stars and planets.
"We found methyl isocyanate in reasonable abundance, so it suggests — and people have been maintaining — this: that comets bring interstellar material into the solar system, and when they bombard planets they bring that material to planet surfaces," Ziurys says.
"This is a very interesting molecule because it’s highly reactive and can lead to all kinds of complicated organic species," she says. "People don’t necessarily make this biological connection to space, but there likely is a strong link to biology. Now that we’ve seen methyl isocyanate out in space and we’ve seen it in a comet in our solar system, we strongly suspect it would be present on other comets and comets that bombarded the Earth billions of years ago.”
Ziurys and Halfen are now on the lookout for interstellar molecules that have prebiotic significance like methyl isocyanate but are even more complex. This work is part of the Earths in Other Solar Systems collaboration at Arizona.
The researchers' results were published online in October in the Astrophysical Journal Letters.