New icy volcanoes on dwarf planet Pluto may be exhibiting a form of cryovolcanism unique to the solar system.

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Unique phenomenon: Analysis of data from NASA’s New Horizons spacecraft suggests a never-before-seen form of icy volcanism may be occurring on the dwarf planet Pluto. Slowly escaping, the viscous water ice eventually piled up mountains up to seven kilometers high, creating ice volcanoes larger than the largest fiery mountains on earth. The young age of some of these formations also suggests that Pluto may still be warm inside today.

dwarf planet Pluto It’s a remarkably dynamic world, despite its remoteness from the sun and its freezing temperatures, as images from NASA’s New Horizons spacecraft show. Glaciers formed by overturning currents flow along it. ice floes and even winch, powered by the release of frozen nitrogen from the great Sputnik Planitia ice sheet. Surface streamers and planetary models also suggest that Pluto’s interior is still warm enough for one person. subglacial ocean or at least could be softened layers of ice.

Picard Mons and Wright MonsThe summit depressions of Picard-Mons (left) and Wright-Mons, viewed from above. © NASA/JHUAPL/SwRI

Riddles about the ice mountain giants

But one question remained unanswered: Are there ice volcanoes on Pluto? This question is suggested by two mountains with large craters on their peaks, located southwest of the icy plain of the Sputnik Plain. With Mount Wright almost five kilometers high and about 150 kilometers wide at the base, this depression at the top even has a diameter of 56 kilometers. Already in 2015, the shape of these mountains woke up. suspicionthat these could be ice volcanoes – vents that bring half-melted ice to the surface.

Kelsey Singer of the Southwestern Research Institute in Boulder and her colleagues are now again looking for evidence of such cryovolcanism on Pluto in data and images from the New Horizons probe. To do this, they first analyzed images in which potential ice volcanoes were illuminated obliquely by weak sunlight, so that surface structures are clearly distinguished by cast shadows.

Unlike known volcanic forms

Result: At least volcanoes and ice volcanoes in the classical sense do not look like Pluto’s mountains, the team reports. The peak troughs of Mons Wright and Picard Mons, which are even higher by seven kilometers, are significantly different from the calderas or volcanic vents on Earth and Mars. Among other things, according to Singer and her colleagues, the holes are too large and irregular in shape and do not correspond to the craters that subsequently collapsed.

“Furthermore, there is no clear evidence of directional flow or the location of exit centers,” the researchers report. There are no traces of material release or sputum discharge. Also strange: The entire terrain of this region, including the mountain slopes and the interior of the crater basins, is covered with hilly hills several hundred meters high and up to 20 kilometers wide – this is also quite unusual for volcanoes and ice volcanoes. .

The area is still relatively young

“Thus, the geological features of the Wright Mons region are different from all other regions of Pluto, as well as from the topography of most other celestial bodies in the solar system,” say Singer and her team. The near absence of impact craters in the area also suggests that the landscape here is relatively young – it must have changed long after the formation of the dwarf planet.

This late formation is confirmed by spectral data. Thus, the main material of these mountains consists of solid frozen water ice covered with a thin layer of organic sediments and more volatile types of ice such as nitrogen ice and frozen methane. According to the researchers, the differences in the thickness and composition of these layers suggest that different parts of this area did not form together, but have different ages.

A new form of cryovolcanism

But how does it all fit together? According to the research team, Wright and Picard Mons, as well as the area between them, could have formed as a result of a new form of cryovolcanism. At the same time, strong, but still mobile, water ice swelled up from several cracks in the bowels and formed dome-shaped elevations there. Over time, these individual domes merged into the hilly landscape that is visible today.

“This scenario provides a coherent explanatory mechanism for all major peaks and troughs—both dome-shaped and ring-shaped and more complex,” write Singer and her colleagues. The two high mountains were formed because several ice outlets were close together and constantly pushing new masses of water ice from the bottom up. The result was huge uplands like Mount Wright and the even larger Mount Picard.

“Monsa Wright alone has a volume of 24,000 cubic kilometers – similar to the volume of Mauna Loa in Hawaii,” the researchers explain.

Indication of internal heat?

If this scenario is confirmed, then a previously unique form of icy volcanism could exist on the dwarf planet Pluto. At the same time, this also means that the interior of Pluto is actually warmer than previously thought. Because this heat is a prerequisite for water ice to become mobile enough to be able to float to the surface even if only slowly.

“The outpouring of icy material on the surface of a celestial body with extremely low temperature, low atmospheric pressure and low gravity, combined with an abundance of volatile ice on the surface of Pluto, makes it unique among all previously explored places in the solar system,” the scientists state. (Nature Communications, 2022; doi: 10.1038/s41467-022-29056-3)

Source: Nature Communications.

March 30, 2022

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