Scientists: New Horizons’ images of Pluto suggest liquid nitrogen flows in the cracks of its frozen nitrogen ocean
From Figure 1 of the paper. DDA stands for
“Diffuse Dark Aprons” while DNF stands for
“Discrete Dark, Narrow Features”.
Using the pictures taken by New Horizons as it flew past Pluto in 2015, scientist now posit that the dark polygon features scene in Sputnik Planitia — the very large heart-shaped ocean of frozen nitrogen that dominates the hemisphere seen by the spacecraft — are caused by liquid nitrogen flowing upward in cracks from below. From the abstract of their paper [pdf]:
The northern extent of [Sputnik Planitia] displays a variety of geomorphological features that can be interpreted as evidence for convective flows in the basin-filling ice sheet. The complete lack of detected craters in [Sputnik Planitia] argues that these processes are ongoing.
The convection cells in northern [Sputnik Planitia] also display sharp, darkened boundaries that are bordered by more diffuse, less darkened zones. We hypothesize that these patterns may be explained as evidence of the flow of liquid N2 [nitrogen] sourced from beneath the glacier. This hypothesis suggests that basal melt of the ice sheet occurs, that this melt reaches the surface before it freezes in transit upward through colder ice, and that the melt has sufficient time before it freezes during flow across the ice surface to fill topographic lows.
Thus, the dark areas around the DNFs in the pictures are examples of liquid nitrogen ponding on the surface as it freezes.
This data provides more evidence that Pluto is active geologically, even though its location so far out in the solar system provides it very little heat or energy from the Sun. It is also further proof that the decision by a small group of scientists at an International Astronomical Union (IAU) meeting in Europe in 2006 to declare Pluto was not a planet was utterly stupid. It was also not supported by the planetary science community, which generally considers any object large enough to become spherical to be a planet.
Pluto is not only spherical, it has an atmosphere and appears to be geologically active. To say it isn’t a planet is like saying a Volkswagen Beetle is not a car because it happens to be small.
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Yes, I had to look it up but N boils at -196C and freezes at -210C. That is a surprisingly narrow range but it might help explain what seems to be going on here.
Those temps for N2 you quote are for 1 atm like on Earth sea level.
Yes, but if that narrow range holds for different pressures it might indicate an active freeze/ thaw cycle.
It’s worth noting nitrogen liquid/solid behave opposite to water/ice — ice is less dense than water (specific gravity 0.92 vs. almost 1.0) but solid nitrogen is more dense than liquid (~1.03 vs. ~0.81). So nitrogen ‘ice’ sinks as a lake of liquid freezes from the top; and melt-liquid underneath a nitrogen ‘glacier’ tends to rise through cracks to the surface, while the solid drops down closer to the heat source.
Yes, Pluto is an alien planet. (Or if one wants to be IAU-pedantic, former planet, the only one ever.)
And anyone who doubts the “Pluto vendetta” was/is real, ought to look up a book called “How I Killed Pluto and Why It Had It Coming” — pretty much a full, book-length confession of grudgingly ill intent.
I got the impression that Pluto was de-planetized because there was no definition that would cover Pluto without also including any number of large Kuiper Belt objects that were being discovered around that time. For some reason, it was unacceptable to count those as planets (too many, constant new discoveries, I dunno,) so Pluto had to go, with the bonus that the big asteroids (Ceres in particular) were clarified as not-planets at the same time.
Also; it’s not nitrogen that is weird where its solid form sinks. It’s water that is weird where its solid form floats; the hexagonal lattice that ice forms has gaps in it. It just seems normal because water is the liquid we interact with most.
Boobah: The reasoning you cite was given by some at the time, but the truth is more ugly. A IAU committee to come up with a definition had proposed something that would have included all the new discoveries, in line with the planetary community’s general desires. (Note that no one questions calling every exoplanet discovered a “planet”.)
The final vote was delayed. As the meeting wound down on its last day, many left, especially the Americans and the members of that committee. A small group remaining at the meeting introduced the new definition, expressly designed to remove Pluto as a planet but to do so in a way that was incoherent and scientifically invalid (no planet clears its orbit), and it passed. There is strong evidence there was an element of Anti-Americanism in the success of this maneuver, as it appears a lot of Europeans remaining simply did not like it that an American had discovered one of the 9 planets.
The average temperature is -229C
33K. (-240C) To 55K (-218C) with almost no atmospheric pressure. (One millionth of a bar? Whatever one Pa is)
I am guessing every impact that occurs produces heat which would quickly melt the surrounding area just to refreeze over the top of the crater. Any seismic movement of the ice sheet would produce just enough heat to allow liquid nitrogen to flow.
I forgot to mention, the melting is probably caused by the gravitational influence of its moons? Just enough pulling and stretching to create a little frictional heat.
Radioactive decay in Pluto’s core might be a contributing factor too.
“There is strong evidence there was an element of Anti-Americanism in the success of this maneuver, as it appears a lot of Europeans remaining simply did not like it that an American had discovered one of the 9 planets.”
Even worse, almost all of those erstwhile planets discovered to that point in the Kuiper Belt had also been discovered or co-discovered by Americans (most prominently, Mike Brown), too.
I have long suspected that myself.
Adding planets to textbooks could have helped raise excitement for space efforts.
Greens hate that, of course.
“Wait It Out” Larry Niven 1968