[meteorite-list] Scientists Study Nitrogen Provision for Pluto's Atmosphere

[Ron Baalke]

http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20150812

Scientists Study Nitrogen Provision for Pluto's Atmosphere
August 12, 2015
          
The latest data from NASA's New Horizons spacecraft reveal diverse features 
on Pluto's surface and an atmosphere dominated by nitrogen gas. However, 
Pluto's small mass allows hundreds of tons of atmospheric nitrogen to 
escape into space each hour.

So where does all this nitrogen come from? Kelsi Singer, a postdoctoral 
researcher at Southwest Research Institute, and her mentor Alan Stern, 
New Horizons principal investigator and SwRI associate vice president, 
outlined likely sources in a paper titled, "On the Provenance of Pluto's 
Nitrogen." The Astrophysical Journal Letters accepted the paper for publication 
on July 15, just a day after the spacecraft's closest encounter with the 
icy dwarf planet.

"More nitrogen has to come from somewhere to resupply both the nitrogen 
ice that is moving around Pluto's surface in seasonal cycles, and the 
nitrogen that is escaping off the top of the atmosphere as the result 
of heating by ultraviolet light from the Sun," said Singer.

Singer and Stern looked at a number of different ways that nitrogen might 
be resupplied. They wondered if comets could deliver enough nitrogen to 
Pluto's surface to resupply what is escaping its atmosphere. They also 
looked at whether craters made by the comets hitting the surface could 
excavate enough nitrogen - but that would require a very deep layer of 
nitrogen ice at the surface, which is not proven. The team also studied 
whether craters could expose more surface area, by punching through surface 
deposits that would likely be built up over time.

"We found that all of these effects, which are the major ones from cratering, 
do not seem to supply enough nitrogen to supply the escaping atmosphere 
over time," continued Singer. "While it's possible that the escape rate 
was not as high in the past as it is now, we think geologic activity is 
helping out by bringing nitrogen up from Pluto's interior."

And while the data weren't in before this paper was written, the newest 
images of Pluto show land forms that suggest heat is rising beneath the 
surface, with troughs of dark matter either collecting, or bubbling up, 
between flat segments of crust, which could be related.

"Our pre-flyby prediction, made when we submitted the paper, is that it's 
most likely that Pluto is actively resupplying nitrogen from its interior 
to its surface, possibly meaning the presence of ongoing  geysers or 
cryovolcanism," said Stern. "As data from New Horizons comes in, we will be 
very interested to see if this proves true."

New Horizons is part of NASA's New Frontiers Program, managed by the agency's 
Marshall Space Flight Center in Huntsville, Ala. The Johns Hopkins University 
Applied Physics Laboratory in Laurel, Md., designed, built, and operates 
the New Horizons spacecraft and manages the mission for NASA's Science 
Mission Directorate. SwRI leads the science mission, payload operations, 
and encounter science planning.