Pluto, the Solar System’s largest dwarf planet, has suddenly gotten a whole lot more intriguing according to reports, that freezing Volcanoes flows have lately covered huge areas of its surface.
In this context, “recently” means probably no more than a billion years ago.
Of course, it’s old – and there’s no evidence that volcanoes are currently active – but it’s only a fifth of the Solar System’s age, and no one knows how Pluto generated the heat needed to power these volcanoes eruptions.
The discovery was made possible thanks to an analysis of images and other data by a team led by Kelsi Singer of the Southwest Research Institute in Boulder, Colorado, nearly seven years after the National Aeronautics and Space Administration’s New Horizons probe made its spectacular flyby of Pluto on July 14, 2015.
The hilly feature known as Wright Mons, which rises 4 km-5 km above its surroundings, is of great interest to Singer’s team.
It has a central depression (a hole) that is 40 km-50 km wide and has a floor that is at least as low as the surrounding landscape. Its base is roughly 150 km long and has a central depression (a hole) that is 40 km-50 km wide.
Wright Mons is a volcano, according to the study, and the lack of impact craters indicates that it isn’t more than 1 billion-2 billion years old.
Many other locations of Pluto have had ample time to amass enormous numbers of impact craters, and no recent frozen volcanoes flows have covered them.
Wright Mons is a large volcano in the world of volcanoes. It has a volume of over 20,000 cubic kilometres.
Although far smaller than the largest volcanoes on Mars, this is comparable to the whole volume of Hawaii’s Mauna Loa and significantly larger than the volume of its above-sea-level part.
This is especially astounding considering Pluto’s diminutive size, which is roughly a third of Mars’ and a sixth of Earth’s.
Volcanoes Wright Stuff on Pluto
The slopes of Wright Mons and much of its environs are crammed with hummocks up to one kilometre high and generally 6 km-12 km broad.
The researchers believe that these hummocks are predominantly formed of water ice, rather than the nitrogen or methane ice that covers certain other Pluto’s youthful regions.
They claim that this is consistent with the material strength required to produce and retain these domes, but they do see small patches of nitrogen ice that are significantly weaker, primarily in the centre depression.
The hummocks were most likely formed by ice volcanoes (technically known as “cryovolcanism”), which erupt in cold water rather than molten rock.
Pluto’s bulk density indicates that it must have the rock in its interior, but its outer regions are made up of ices (water, methane, nitrogen, and possibly ammonia and carbon monoxide, all of which are less than a third as dense as a rock), much like the Earth’s and other rocky planets’ crusts are made up of a variety of silicate minerals.
Ice built of frozen water is extremely strong at Pluto’s surface temperature of well below minus 200 degrees Celsius. It can (and does) produce towering mountains that last an eternity on Pluto, rather than slumping downhill like a glacier on Earth, where water-ice is weaker.
Ice, unlike rock, melts at considerably lower temperatures. Furthermore, the melting of a mixture of two pieces of ice can begin at a lower temperature than the melting of either of the pure ices (the same principle applies in silicate rock made of different minerals). This facilitates melting even more.
Despite this, the discovery of evidence of relatively youthful water-rich cryovolcanic eruptions on Pluto is surprising, given the lack of a known heat source.
Tidal forces – a gravitational effect between orbiting entities, such as a moon and a planet – which warm the interiors of some of Jupiter’s and Saturn’s moons – have only a small chance of heating Pluto’s innards.
And there isn’t enough rock inside Pluto to generate much heat from radiation to form volcanoes.
Singer and her colleagues suggest that Pluto retained heat from its birth, which was unable to escape until later in its life. This would be consistent with other data suggesting Pluto has a deep interior liquid water ocean.
If the hummocks that form Wright Mons are water-ice eruptions, the fluid was clearly not flowing freely like liquid water, but rather as a gooey crystal-rich “mush,” possibly contained within a completely frozen, but still pliable, outer skin that confined each effusion of fluid into a dome-like hummock.
The team uses the depth and volume of Wright Mons’ central depression to refute previous claims that it is a volcanoes crater (a caldera) or that it was carved out by explosive eruptions. Instead, they see it as a void that has escaped being filled in by erupted hummocks.
Piccard Mons is less well known than Wright Mons because Pluto’s rotation had cast Piccard Mons into darkness by the time New Horizons arrived at its closest approach. Only the side of Pluto facing the Sun at the right time could be viewed in detail due to the speed of the flyby.
Piccard Mons, on the other hand, was imaged by New Horizons thanks to sunlight reflected weakly onto the ground by haze in Pluto’s atmosphere.
That was an incredible achievement, but we’re curious to learn more. What hidden details are there in Pluto’s poorly photographed half? We will most likely have to wait decades to learn much more about how these frozen volcanoes developed.