Nav: Home

Neptune's moon Triton fosters rare icy union

May 22, 2019

Astronomers using the Gemini Observatory explore Neptune's largest moon Triton and observe, for the first time beyond the lab, an extraordinary union between carbon monoxide and nitrogen ices. The discovery offers insights into how this volatile mixture can transport material across the moon's surface via geysers, trigger seasonal atmospheric changes, and provide a context for conditions on other distant, icy worlds.

Extreme conditions can produce extreme results. In this case, it's the uncommon pairing of two common molecules -- carbon monoxide (CO) and nitrogen (N2) -- frozen as solid ices on Neptune's frigid moon Triton.

In the laboratory, an international team of scientists have pinpointed a very specific wavelength of infrared light absorbed when carbon monoxide and nitrogen molecules join together and vibrate in unison. Individually, carbon monoxide and nitrogen ices each absorb their own distinct wavelengths of infrared light, but the tandem vibration of an ice mixture absorbs at an additional, distinct wavelength identified in this study.

Using the 8-meter Gemini South Telescope in Chile, the team have recorded this same unique infrared signature on Triton. Key to the discovery was the high-resolution spectrograph called IGRINS (Immersion Grating Infrared Spectrometer) which was built as a collaboration between the University of Texas at Austin and the Korea Astronomy and Space Science Institute (KASI). Both the Gemini Observatory and IGRINS receive funding from the US National Science Foundation (NSF) and KASI.

"While the icy spectral fingerprint we uncovered was entirely reasonable, especially as this combination of ices can be created in the lab, pinpointing this specific wavelength of infrared light on another world is unprecedented," said Stephen C. Tegler of Northern Arizona University's Astrophysical Materials Laboratory who led the international study. The research results have been accepted for publication in the Astronomical Journal.

In the Earth's atmosphere carbon monoxide and nitrogen molecules exist as gases, not ices. In fact, molecular nitrogen is the dominant gas in the air we breath, and carbon monoxide is a rare contaminant that can be lethal.

On distant Triton, however, carbon monoxide and nitrogen freeze as solid ices. They can form their own independent ices, or can condense together in the icy mix detected in the Gemini data. This icy mix could be involved in Triton's iconic 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 back in 1989. Since then, theories have focused on an internal ocean as one possible source of erupted material. Or, the the geysers may erupt when the summertime Sun heats this thin layer of volatile ice on Triton's surface, potentially involving the mixed carbon monoxide and nitrogen ice revealed by the Gemini observation. That ice mixture could also migrate around the surface of Triton in response to seasonally varying patterns of sunlight.

"Despite Triton's distance from the Sun and the cold temperatures, the weak sunlight is enough to drive strong seasonal changes on Triton's surface and atmosphere," adds Henry Roe, Deputy Director of Gemini and a member of the research team. "This work demonstrates the power of combining laboratory studies with telescope observations to understand complex planetary processes in alien environments so different from what we encounter every day here on Earth."

Seasons progress slowly on Triton, as Neptune takes 165-Earth years to orbit the Sun. A season on Triton lasts a little over 40 years; Triton passed its southern summer solstice mark in 2000, leaving about 20 more years to conduct further research before its autumn begins.

Looking ahead, the researchers expect that these findings will shed light on the composition of ices and seasonal variations in the atmosphere on other distant worlds beyond Neptune. Astronomers have suspected that the mixing of carbon monoxide and nitrogen ice exists not only on Triton, but also on Pluto, where the New Horizons spacecraft found the two ices coexisting. This Gemini finding is the first direct spectroscopic evidence of these ices mixing and absorbing this type of light on either world.


Triton orbits Neptune, the eighth planet from the Sun, some 2.7 billion miles from Earth -- at the cold outer fringe of our Solar System's major planet zone. It is the only large moon in the Solar System that orbits "backwards" or in the opposite direction to its planet's rotation. The peculiar motion suggests that Triton is a captured trans-Neptunian object from the Kuiper Belt -- a region of leftovers from the Solar System's early history, which is why it shares several features with the dwarf planet Pluto and Eris: size (roughly two-thirds that of our Moon), and surface temperatures that hover near absolute zero; so low that common compounds we know as gases on Earth freeze into ices.

Triton's atmosphere is also 70,000 times less dense than Earth's and is composed of nitrogen, methane, and carbon monoxide. Its surface appears to consist of two different terrains, one composed by the volatile ices and the second one formed by water and carbon dioxide ices.

Molecular nitrogen is thought to have been the most common type of nitrogen available when the Solar System was forming. Its abundance in the outer Solar System is an important key to life's origins, as it is an important part of the building blocks of life.
Science Contacts:
Stephen Tegler
Northern Arizona University, Professor of Physics & Astronomy
cell phone: 928-607-3979
desk phone: 928-523-9382

Henry Roe
Gemini Observatory, Gemini South Deputy Director
desk phone: +56 (51) 2205603

Media Contacts:
Peter Michaud
Gemini Observatory, PIO Manager
cell phone: 808-936-6643
desk phone: 808-974-2510

Kerry Bennett
Northern Arizona University, Research Communications Officer
desk phone: 928-523-5556


The Gemini Observatory is a facility of the National Science Foundation (NSF-United States), the National Research Council (NRC-Canada), the Comisión Nacional de Investigación Científica y Technológica (CONICYT - Chile), the Ministério da Ciência, Tecnologia e Inovação (MCTI - Brazil), the Ministerio de Ciencia, Technología e Innovación Productiva (MCTIP - Argentina), and the Korea Astronomy and Space Science Institute (KASI - Republic of Korea), operated under cooperative agreement by the Association of Universities for Research in Astronomy, Inc. (AURA).

The international Gemini collaboration provides access to two identical 8-meter telescopes. The Frederick C. Gillett Gemini telescope is located on Maunakea, Hawai'i (Gemini North) and the Gemini South telescope is on Cerro Pachón in central Chile; together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space. The Observatory provides the astronomical communities in each of the five participating countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country's contribution. In addition to financial support, each country also contributes significant scientific and technical resources.

Association of Universities for Research in Astronomy (AURA)

Related Solar System Articles:

From rocks in Colorado, evidence of a 'chaotic solar system'
Plumbing a 90 million-year-old layer cake of sedimentary rock in Colorado, a team of scientists from the University of Wisconsin-Madison and Northwestern University has found evidence confirming a critical theory of how the planets in our solar system behave in their orbits around the sun.
Why are there different 'flavors' of iron around the Solar System?
New work from Carnegie's Stephen Elardo and Anat Shahar shows that interactions between iron and nickel under the extreme pressures and temperatures similar to a planetary interior can help scientists understand the period in our Solar System's youth when planets were forming and their cores were created.
Does our solar system have an undiscovered planet? You can help astronomers find out
ASU's Adam Schneider and colleagues are hunting for runaway worlds in the space between stars, and citizen scientists can join the search with a new NASA-funded website.
Rare meteorites challenge our understanding of the solar system
Researchers have discovered minerals from 43 meteorites that landed on Earth 470 million years ago.
New evidence on the formation of the solar system
International research involving a Monash University scientist is using new computer models and evidence from meteorites to show that a low-mass supernova triggered the formation of our solar system.
More Solar System News and Solar System Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#534 Bacteria are Coming for Your OJ
What makes breakfast, breakfast? Well, according to every movie and TV show we've ever seen, a big glass of orange juice is basically required. But our morning grapefruit might be in danger. Why? Citrus greening, a bacteria carried by a bug, has infected 90% of the citrus groves in Florida. It's coming for your OJ. We'll talk with University of Maryland plant virologist Anne Simon about ways to stop the citrus killer, and with science writer and journalist Maryn McKenna about why throwing antibiotics at the problem is probably not the solution. Related links: A Review of the Citrus Greening...