Pluto – Round Two

The images released today from New Horizons indicate the presence of carbon monoxide on the surface, possible wind erosion features, and the atmospheric loss of nitrogen.

In the heart shaped region of Pluto (dubbed Tombaugh Regio for now), New Horizons mapped a region of solid carbon monoxide ice.  Right now, it cannot be determined how extensive the carbon monoxide is.  It might be a sheen on the surface or it might be several meters deep.  We’ll find out more as the rest of New Horizons data comes in.  A map of the carbon monoxide ice is below:


Carbon monoxide (CO) differs from carbon dioxide as it only has one oxygen atom in its molecule instead of two.  Unlike carbon dioxide, CO is not a greenhouse gas.  That aside, carbon monoxide is pretty nasty stuff to be around.  If you live in a house that does not ventilate well, carbon monoxide poisoning is a serious threat.  On Earth, CO is emitted into the atmosphere by inefficient burning processes. This includes combustion engines and industrial emissions along with burning of forests.  Burning in the Amazon and in Africa releases large amounts of CO on a seasonal basis as can be seen on NASA’s Earth Observatory time lapse map of CO.

Unlike Pluto, we do not experience CO as an ice on Earth.  The freezing point of CO is -3370 F (-2050 C), so one has to go out into the furthest regions of the Solar System to see it in that form.  Comets originate from that region and have CO ice.  The gas in Halley’s Comet’s tail emanating from its solid nucleus during its last pass in 1986 was measured to be 10% CO.  Occasionally, Earth will pass through the tail of Halley’s Comet such as on the night of May 18, 1910.  However, the material in the comet’s tail is much too tenuous to have any effect on life.  The New York Times report on the events of that night can be found here.

CO gas does exist beyond the Solar System in the plane of the Milky Way.  Galactic CO was mapped by the ESA Planck mission and the results are below.  Where there is CO, there is hydrogen gas in far more abundance.  CO radiates more readily than hydrogen and serves as a useful guide for mapping galactic gas clouds where star formation occurs.

Credits: ESA/Planck Collaboration

Also within Tombaugh Regio, this interesting image was released:


Which might remind you of what you see in your backyard after a dry spell:

Image: Wiki Commons

As mud dries, it contracts and begins to crack.  A similar process on a much larger scale may have caused the segment formation on Pluto.  Another process that is theorized is the formations are caused by convection below the surface.  Subsurface heat would cause the ground to bubble up.  Right now, the data is too fresh to know for sure which geologic process caused these formations.  As more and more data comes in (only 1 gigabyte of 50 has been received from New Horizons), scientists will get a better handle on what exactly is going on here.


The final discovery announced today was the atmospheric loss experienced by Pluto.  Atmopsheric loss occurs when molecules attain escape velocity.  The lighter the molecule, the easier it is for heat to accelerate it enough to escape into space.  Mercury practically has no atmosphere as its closeness to the Sun imparts enough heat energy to any gas molecule on the surface to escape.  Both Venus and Mars lack the magnetic field Earth has which allows the solar wind to directly interact with the atmosphere and drag it away just like you see above with Pluto.  The video below describes the process on Venus:

Earth loses 50,000 tons of atmosphere a year.  Most of it is hydrogen and helium.  As these are the two lightest of the elements, they most easily reach escape velocity and leave our planet.  Worry not, at that rate, the Sun will turn into a red giant and swallow the Earth five billion years from now before our atmosphere is lost.

Pluto is losing atmosphere at a rate of 500 tons an hour or over 4,000,000 tons a year.  Projected over the course of Pluto’s lifetime, that equates to over a thousand feet of nitrogen ice lost.

As mentioned before, Pluto is pretty cold.  How does the nitrogen in its atmosphere acquire enough energy to escape.  At the mission update, it was explained that the greenhouse gas methane may trap just enough heat to give nitrogen atoms a boost into space.  The other part of the equation is Pluto’s small mass, only 0.002 of Earth’s.  This means Pluto’s escape velocity is 1.3 km/s compared to Earth’s 11.2 km/s.  Thus, it is much easier for nitrogen to escape Pluto than it is to escape Earth.  Pluto lacks a significant magnetic field and direct contact with the solar wind accelerates atmospheric loss.

One of the most important aspects of studying astronomy is to gain a greater perspective on Earth.  Looking at the atmospheric loss on Pluto and other planets in the Solar System, it can give a greater appreciation of the role the magnetic field here on Earth plays in protecting life.  The Pluto flyby is a great adventure, but it also goes to show, there is no place like home.

*Image on top of post is best Hubble image of Pluto vs New Horizons image. Credits: Hubble: NASA / ESA; New Horizons: NASA / JHU-APL / SWRI

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