Clues to Pluto’s History Lie in Its Faults (EOS Science News from the AGU). A news item from the American Geophysical Union summarizes research by the Lunar and Planetary Institute. They decided that the “cold Pluto” theory doesn’t explain the young features, so a “hot Pluto” model is needed— with a little help from (Incoming rock alert!… WHAM!!) impactors.
This liquid water ocean has huge implications for how
Pluto formed and retained enough heat to melt all that ice. In the years since the New Horizons flyby, two general formation hypotheses have emerged. The first starts with a “cold” Pluto, which involves Pluto forming over millions of years by the slow accretion of cold objects. This version of Pluto eventually would have coalesced enough material that radiative heating from the inside would melt the subsurface ocean. The other hypothesis involves a “warm” or “hot” Pluto, in which Pluto formed over a shorter time period in violent collisions that heated its interior, formed the ocean, and eventually cooled the planet into the majority ice ball we know today.
If Pluto had formed by slow accretion (the old standard theory), its only heat source would have been radiogenic heat. All the short-period radionuclides should have burned out long ago. Another source of heat out in the solar system’s icebox zone comes from the kinetic energy of impacts."
Let’s see if they can keep Pluto billions of years old. Feel the surprise at Pluto’s revelation during the flyby:
Following its flyby of the Pluto-Charon system in 2015, NASA’s New Horizons spacecraft returned high quality images that revealed complex worlds with an unexpectedly diverse range of terrains and a correspondingly diverse range of resurfacing mechanisms, including broad tectonic systems, suggestions of cryovolcanic activity, and even ongoing surface renewal in the form of the convecting and glacially flowing nitrogen ice deposits of Sputnik Planitia on Pluto (Moore et al., 2016; Stern et al., 2015).
Such processes should not be going on so far away from the sun. Have they been steady for billions of years?
Global climate modeling of Pluto (Bertrand et al., 2018) indicates that the massive scale of the Sputnik basin would cause it to be filled by nitrogen ice migrating into it from across Pluto after its excavation over a timescale of some tens of millions of years (less than 1% of Pluto’s total age). If the basin is filled so rapidly, it follows that the formation of the Sputnik basin and its subsequent infilling (i.e., loading) are essentially coincidental to within some tens of millions of years.
Notice the assumption: “1% of Pluto’s total age.” That embeds the
4.5-billion-year age assumption into the discussion. They take it as
undisputed fact, but if the impact occurred near the beginning of
Pluto’s old-age story, and if Sputnik Planitia filled in within tens of
millions of years (several 450ths of the assumed age), why is activity
still going on today?" CEH