New Horizons - The Pigeon Roost

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.

Also within Tombaugh Regio, this interesting image was released:

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

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

The first thought I had watching the press conference on the initial images from the New Horizons flyby of Pluto was how much accessible these events are to the public than in the days of Voyager. During the 1980’s, unless you had a NASA press pass, you did not get to watch mission updates live. No twitter feeds to tell you right away when telemetry is being received, no websites to go back and review the images at your leisure. And you had to wait at least a year, maybe more, for astronomy textbooks to be updated. What you got was short segments on the nightly news such as this:

One of my favorite teaching techniques is to compare the surface features of planets to things we are familiar with here on Earth to give it proper perspective. And that seems to me to be a good place to start with the first images released today.

Lets begin with the mountains located near the now famous heart-shaped region of Pluto.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

This image was taken while New Horizons was 77,000 km away from Pluto. That’s 10 times farther away than the closest approach and gives a good idea what to look forward to as more images are released.

The tallest of these mountains are about 11,000 feet (3,500 m). How does this compare to Earth? These are less than half as tall as Mt. Everest which clocks in at 29,029 feet. Still, pretty impressive mountains considering how small Pluto is. The height of these mountains are similar to Mt. Hood in Oregon.

The first age estimate of these mountains are about 100 million years. That sounds pretty old. In fact, dinosaurs were roaming around on Earth when these mountains formed. In geological terms, this is pretty young, only 2% the age of the Solar System (4.5 billion years). How do we know these mountains are young? By the lack of craters in the region. The less craters there are, the younger a surface is. These mountains are younger than the Alps which are 300 million years old. They are older than the Himalayan Mountains which formed as the Indian Sub-Continent plowed into Asia 25 million years ago.

Mountains on Earth are the result of plate tectonics. At this very early juncture, planetary scientist have their work cut out for them as none of the current models can account for such mountain formation on an icy outer Solar System body in the absence of tidal flexing. It is thought that the mountains are regions of water-ice bedrock poking through the methane ice surface. Methane ice is too weak to build mountainous structures.

Below is Pluto’s largest moon Charon:

The outstanding feature here is the large canyon in the upper right corner. This canyon is 4 to 6 miles (7 to 9 km) deep. The Grand Canyon’s greatest depth is a little over a mile. This channel is comparable to the deepest reaches of the Pacific Ocean, the Mariana Trench, that lies about 6.8 miles below sea level. It’s interesting to consider than more humans have walked the surface of the Moon (12) than have reached the bottom of the Mariana Trench (3). To be fair, no nation has ever decided to spend $150 billion (2015 dollars) and employ 400,000 people to reach the Mariana Trench, such as the United States did during the Apollo program.

This image maps methane on the surface of Pluto.

The New Horizons press release describes the greenish area of Pluto’s North Pole as methane ice diluted in nitrogen ice. Does that sound odd? Typically, we see neither of these substances in a solid state on Earth. Methane and nitrogen are known as volatiles, which means they take gaseous form at room temperature. As you may have surmised, Pluto is not at room temperature. The freezing point of methane is -295.6⁰ F (-182⁰ C) on Earth. The freezing point of nitrogen is even lower at -346⁰ F (-210⁰ C). These figures are lower on Pluto as the atmospheric pressure does not match that of Earth. The temperature of Pluto ranges from -387⁰ to -369⁰ F (-233⁰ to -223⁰ C). Yeah, the outer reaches of the Solar System are pretty chilly.

In our day to day lives, you may be familiar with methane as the main component of natural gas. You may have learned about it first as a source of middle school humor. While methane is a gas on Earth, the Saturn moon Titan is cold enough for it to be a liquid. Below is an image of methane lakes on Titan. Instead of raining water, you could dance in the methane rain on Titan. Earth and Titan are the only bodies in the Solar System to have stable liquid lakes on the surface.

Neptune has trace amounts of methane in its atmosphere. Methane has the property of absorbing red light and scattering blue light. The result is the rich blue hue of Neptune as first seen in the 1989 Voyager flyby:

Methane also absorbs infrared light at certain wavelengths. The methane profile image of Pluto was produced by measuring infrared absorption from surface methane. When methane absorbs infrared light at these wavelengths, the infrared energy is converted in vibrational motion in the molecular bonds. Once the molecule settles down, the energy is released back out as infrared light. We cannot see infrared light, but we feel it as heat. In the atmosphere, some of this heat is directed back towards the Earth, warming the surface. In other words, methane is a greenhouse gas like carbon dioxide and water vapor.

And for that, we should be grateful. Without greenhouse gasses, the Earth would be 60⁰ F colder (like the Moon), and human life would not be possible. However, you can have too much of a good thing. As temperatures rise in the Arctic warming up the permafrost, methane that has been locked up for thousands of years as frozen, undecomposed plant life, could be released into the atmosphere. When you consider the Arctic region has been most affected by rising global temperatures, then you can understand why climate scientists are concerned about this scenario.

On Friday, New Horizons should be releasing the first color images from the flyby. Should be quite an interesting week.

*Image on top shows part of Pluto’s heart region the mountain closeup was taken. Credit: NASA

Tag: New Horizons

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