Strange Ice

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“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 in infrared light on another world is unprecedented,” commented Dr. Stephen C. Tegler in a May 22, 2019 Gemini Press Release. Dr. Tegler, of Northern Arizona University’s Astrophysical Materials Laboratory, led the international study based on Gemini Observatory observations. The research results are published in the Astronomical Journal.

In our own planet’s atmosphere, carbon monoxide and nitrogen molecules exist as gases–not ices. They can form their own distinctive ices, or they can condense together to form the icy mixture spotted in the Gemini data. This exotic mixture of ices may play an important role in Triton’s famous geysers, first seen in Voyager 2 spacecraft images as dark windblown streaks tearing through Titan’s otherwise bright, icy surface.

The Voyager 2 spacecraft first detected Triton’s geysers, in the act of erupting in the moon’s south polar region, back in 1989. Since then, numerous explanatory theories have been devised that have suggested the possible existence of a subsurface ocean as one potential source of the erupted material. Or, alternatively, the geysers may erupt when the feeble heat of Neptune’s summer warms the slender layer of volatile ice on Triton’s surface–possibly involving the carbon monoxide and nitrogen ice mixture recently revealed by the Gemini observation. That icy mixture could also travel around Triton’s surface as a result of seasonally altering patterns of distant 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. 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,” explained Dr. Henry Roe in the May 22, 2019 Gemini Press Release. Dr. Roe is Deputy Director of Gemini and a member of the research team.

The seasons change slowly on Triton, because Neptune takes 165 Earth-years to make a single orbit around our Star. One season on Triton lasts a little longer than 40 years. Triton passed its southern summer solstice back in 2000, leaving two decades more for astronomers to continue to conduct their research before autumn comes to this distant, dimly-lit and exotic moon-world.

In the future, the team of astronomers expect that their discoveries will shed new light on the composition of ices and seasonal alterations occurring in the atmospheres of other remote worlds beyond Neptune. Scientists have suspected that this strange mixture of carbon monoxide and nitrogen ices also exists on Pluto–as indicated by the recently visiting New Horizons spacecraft. The new Gemini findings provide the first direct spectroscopic evidence that these ices mix together on these two kindred and remote frozen worlds.

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