(NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute)
The New Horizons team confirmed that Pluto's Mounts Wright and Piccara are indeed the result of cryovolcanism, and not erosion or normal uplift.
It is assumed that several large subsurface sources of cryomagma participated in their creation, and Pluto itself retained heat in its depths longer than previously thought.
The surface of Pluto, the largest object in the Kuiper Belt, shows a very diverse morphology, which suggests that it has been subjected to intense and constant renewal through endogenous and exogenous processes.
It is assumed that the outer layer of the dwarf planet, about 300 kilometers thick, is rich in water ice, and a water ocean may still exist at the base of the ice shell.
The typical surface temperature of Pluto is 35-60 Kelvin, under such conditions, pure water ice should form immobile bedrock, but impurities of ammonia or salts can reduce the melting point of ice.
In addition, the melting point of nitrogen ice (63 kelvin) allows it to be more dynamic than water ice, such as flowing slowly.
Ice from methane or carbon monoxide, which can sublimate, undergo physical erosion or re-deposit on the surface of the planet from the atmosphere, also contributes to the renewal of the surface of the dwarf planet.
Another important process associated with ice and capable of influencing the relief of Pluto is cryovolcanism.
Previously, in images taken by the New Horizons probe, scientists have already found candidates for the largest cryovolcanoes in the solar system.
However, it is not known when they were active, and what are the features of the course of cryovolcanism on Pluto.
The study
A team of planetary scientists led by Kelsi Singer of the Southwestern Research Institute has published the results of an analysis of New Horizons images of Pluto
The studies refer to a region of suspected cryovolcanic landscapes southwest of the Sputnik Plain.
Singer and her colleagues wanted to study the mechanisms that shaped this area and date it.
The most noticeable structures in the cryovolcanic region were large uplifts separated by wide depressions.
Two of them, similar to volcanoes, with deep central depressions, received the designations Mount Wright and Mount Piccard.
The height of Mount Wright reaches 4-5 kilometers, and the width is 150 kilometers, Mount Piccara - 7 and 225 kilometers, respectively.
The estimated volume of the main part of Mount Wright is 2.4x104 cubic kilometers, which is similar to the Mauna Loa volcano on Earth.
The central depression of Mount Wright has a diameter of 40–50 kilometers and an approximate depth of 4 kilometers.
The central depression of Mount Piccara is larger than that of Mount Wright and has a more rounded or "U" profile.
It does not look like the calderas of Earth or Martian volcanoes, and its walls have a lumpy structure, like the outer boundaries.
The slopes of Mount Wright and much of the surrounding landscape, including the nearby highlands, have an undulating and/or bumpy structure, with wave sizes varying from a few kilometers to 20 kilometers across.
Scientists did not find obvious signs of directed flows that could be erupted by cryovolcanoes, obvious traces of explosive volcanism or local sources of eruptions in the images.
However, they came to the conclusion that the central depressions could not be formed due to the usual collapse of mountain peaks, and traces of cryovolcanism could be erased from time.
The rarity of craters on Mount Wright indicates its relatively young age, with an upper limit of 1–2 billion years.
The surface contains nitrogen, methane, and water ice, as well as dark organic matter represented by tholins.
(Kelsi N. Singer et al. / Nature Communications, 2022)
Conclusions
The researchers concluded that the observed uplifts were formed as a result of the deposition of matter on the surface of the planet through cryovolcanism and are not remnants of mountain erosion or structures created by uplift.
Geological features in the Mount Wright region are morphologically unlike any other regions of Pluto, and also have very little in common with most landscapes on other bodies in the solar system.
It is assumed that there was a sequential mechanism for the formation of all large uplifts and depressions.
During those upliftings several subsurface sources of cryolava were involved, pouring out a total of more than a thousand cubic kilometers of matter, and some uplifts could merge together.
The existence of such large sources of cryovolcanism suggests that Pluto somehow generated more internal heat, or retained it much longer than previously thought.
Source:
- Nature Communications: https://www.nature.com/articles/s41467-022-29056-3
- EarthSky: https://earthsky.org/space/giant-ice-volcanoes-pluto-new-horizons/
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