A new analysis led by Southwest Research Institute (SwRI) suggests that liquid nitrogen may be moving upward through cracks and reaching the surface of Pluto near the northern edge of Sputnik Planitia, the enormous heart-shaped glacier that dominates part of the dwarf planet. The findings provide the first evidence that liquid has flowed on Pluto in relatively recent times. The research is based on observations from NASA's New Horizons spacecraft and was led by SwRI Associate Vice President Dr.
Alan Stern, principal investigator of the New Horizons mission. "Pluto never stops surprising us," Lead Author Stern said, "and this new result certainly does that. In addition to suggesting that liquids have recently expressed themselves on Pluto's surface, it also suggests a new kind of time-variable feature on Pluto." Strange Dark Features on Pluto's Giant Glacier Sputnik Planitia is a vast glacier made largely of frozen nitrogen and is bigger than Texas and Oklahoma combined.
Images collected by New Horizons in 2015 and 2016 showed that its northern region contains city-sized geologic convection cells separated by thin dark lines and broader, more diffuse dark patches. A new examination of those features suggests that they may occasionally become temporarily wet. The most likely source is liquid nitrogen rising from below the surface.
The findings have been published in the peer-reviewed Planetary Science Journal. Liquid nitrogen cannot fall as rain on Pluto because the dwarf planet's temperature and atmospheric conditions do not allow it. Even so, parts of northern Sputnik Planitia have been darkened in patterns that resemble features seen on terrestrial glaciers after they are exposed to rainwater or to liquid emerging from beneath the ice.
To investigate the resemblance, the SwRI-led team compared images from New Horizons with NASA Landsat 9 images of icy regions on Earth, including Greenland's ice sheet. On Greenland, narrow dark markings appear in places where liquid water is present on top of ice and snow. Similar patterns appear on Sputnik Planitia, leading researchers to propose that subsurface liquid, specifically nitrogen, may be rising upward and wetting Pluto's frozen nitrogen surface.
"The surface of Sputnik Planitia is quite young, probably less than one million years based on modeling of the surface overturn, and thus these features that we are looking at must have formed since then," said SwRI Principal Scientist Dr. Kelsi Singer, one of the study's co-authors. "Pluto has many unique terrains seen nowhere else in the solar system, and this area of Sputnik Planitia is one of them.
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