There are many complex worlds in our Solar System. Some may seem inhospitable, alien and unknown to us, but astronomers use the amazing technological devices at their fingertips to learn about them.
One of them is the Gemini Observatory, which explores Neptune’s intriguing moon Triton, the largest satellite of this gaseous planet. There, scientists have just reported the observation, for the first time beyond the laboratory, of the bond between carbon monoxide and icy nitrogen .
The discovery offers insight into how this volatile mix can carry material across the moon’s surface through geysers , trigger seasonal atmospheric changes, and provide context for conditions on other distant, icy worlds.
A unique and specific wavelength in another world
Why is this discovery extraordinary? In this case, it is a rare combination of two common molecules, carbon monoxide (CO) and nitrogen (N2), frozen in the fragile Triton. Which leads us to believe that extreme conditions can produce extreme results.
Previously, in the laboratory, an international team of scientists had identified a very specific wavelength of infrared light that is absorbed when carbon monoxide and nitrogen molecules come together and vibrate in unison. Individually, the carbon monoxide and nitrogen ions absorb their own different wavelengths from infrared light, but the ‘tandem’ vibration of this icy mixture is absorbed at an extra wavelength, which we did not have , and identified for the first time in this study.
Using the Gemini South Telescope in Chile, the team has recorded this same unique infrared trail on Triton . The key to the discovery was the high-resolution spectrograph called IGRINS (Infrared Immersion Grating Spectrometer) that was built as a collaboration between the University of Texas at Austin and the Korea Space Science and Astronomy Institute (KASI).
” The location of this specific wavelength of infrared light in another world is unprecedented, ” according to Stephen C. Tegler of the University of Northern Arizona, who led the international study. The research results have been accepted for publication in the Astronomical Journal.
What happens on Earth?
In Earth’s atmosphere, carbon monoxide and nitrogen molecules exist as gases, not ice. In fact, molecular nitrogen is the dominant gas in the air we breathe, and carbon monoxide is a somewhat rare pollutant that can be lethal.
In distant Triton, however, carbon monoxide and nitrogen freeze like ice.
This icy mix could be involved in the iconic Triton geysers first seen in Voyager 2 spacecraft images as dark, windblown streaks on the surface of the distant, icy moon.
The Voyager 2 spacecraft first captured Triton’s geysers in action in the moon’s south polar region in 1989. Since then, theories have focused on the existence of a possible internal ocean as the source of the erupted material. Another possibility is that geysers could erupt when the Sun heats this thin layer of volatile ice on Triton’s surface, which could involve the mixture of carbon monoxide and nitrogen ice revealed by the Gemini observation. That mixture of ice could also migrate around Triton’s surface in response to different patterns of sunlight depending on the season.
But isn’t Neptune too far from the Sun for this to happen? Henry Roe, a member of the research team, clarifies: ” Despite Triton’s distance from the Sun and the low temperatures , the weak sunlight is enough to drive strong seasonal changes in Triton’s surface and atmosphere.”
The seasons progress slowly on Triton, as it takes Neptune the equivalent of 165 Earth years to orbit the Sun. A season on Triton lasts a little over 40 years; Triton passed its summer solstice mark in 2000, leaving about 20 more years for further research before its fall begins.
About Triton
Triton orbits Neptune, the eighth planet from the Sun, about 4.345 million kilometers from Earth, in the cold outer fringe of the main planet area of our Solar System. It is the only large moon in the Solar System that orbits “backward” or in the opposite direction to the rotation of its planet.
Its peculiar movement suggests that Triton is a trans-Neptunian object captured from the Kuiper Belt, a region left over from the early history of the Solar System, thus sharing several characteristics with the dwarf planet Pluto and Eris: (about two-thirds the size of our Moon), and surface temperatures that are around absolute zero ; so low that common compounds we know as gases on Earth freeze into ice.
Triton’s atmosphere is also 70,000 times less dense than Earth’s and is made up of nitrogen, methane, and carbon monoxide. Its surface appears to consist of two different terrains, one made up of volatile ice creams and the second made up of water and carbon dioxide.
Molecular nitrogen is believed to have been the most common type of nitrogen available when the Solar System formed. Its abundance in the outer Solar System is an important key to the origins of life, as it is an important part of the building blocks of life.
