Frozen pond on Pluto

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Cool image time! The New Horizons’ science team on Thursday released a new image, showing a remarkable frozen pond on Pluto. As they note:

“In addition to this possible former lake, we also see evidence of channels that may also have carried liquids in Pluto’s past,” said Alan Stern, Southwest Research Institute, Boulder, Colorado—principal investigator of New Horizons and lead author of a scientific paper on the topic submitted to the journal Icarus.

This feature appears to be a frozen, former lake of liquid nitrogen, located in a mountain range just north of Pluto’s informally named Sputnik Planum. Captured by the New Horizons’ Long Range Reconnaissance Imager (LORRI) as the spacecraft flew past Pluto on July 14, 2015, the image shows details as small as about 430 feet (130 meters). At its widest point the possible lake appears to be about 20 miles (30 kilometers) across.

I have not posted the image here, because I have already posted this image on Behind the Black, back on October 6, 2015, in which I wrote in part,

The image shows what looks like an enclosed lake of some material, probably nitrogen, with the bedrock entrapping it solid ice. In addition, as you move away from the shore and head uphill it looks like you travel across several geological layers made of different materials. Figuring out how they formed in this way could probably keep a geologist busy for his or her entire life.

I had also then noted how I expected the scientists would be “drooling” over this image, and that I expected a full press release on it at some point. It took six months, but here we are.


  • Dick Eagleson

    All right! We have a venue for all the skating events of the 2218 Winter Games!

  • Rocco

    Do we know the surface pressure to keep the Nitrogen in a frozen state? I am wondering about the psi since we know the cold is there and we need both to make a solid form. At least here on Earth anyway.

  • Local Fluff

    Pluto’s air pressure is 1/100,000 of that on Earth. It is vacuum. The atmosphere is only interesting for tiny material transports over geological times. Nitrogen freezes at about 60 Kelvin regardless of pressure. But it doesn’t get very hard, water ice is believed to build up the mountains on Pluto, only covered by nitrogen.

  • Rocco

    @Local Fluff
    Yes I get the water below the surface may still be around, but against the vacuum it would sublimate off planet. I guess my question is, does Nitrogen sublimate like water when exposed to a vacuum if not already in a solid form?

  • Edward

    Water sublimation stops below a certain temperature. The vapor pressure drops too low for there to be measurable sublimation. This happens with many substances, such as iron, which does not sublimate at room temperature. If my (faulty) memory (mis)serves me, the temperature at which water stops sublimating is around -150 centigrade.

    Because vapor pressure for substances disappears at cold temperatures, the atmosphere for Pluto disappears when it gets too far from the sun, and the New Horizons scientists wanted to send the probe to Pluto before the atmosphere condensed back onto the surface. There was urgency during the proposal, assembly, and launch phases of the project, and it was this urgency that is why Pluto was put ahead of other proposals. Missing the atmosphere this decade would have required another couple of centuries of waiting for the next opportunity to get a look at it. It is also why they chose to use their weight budget for additional instruments rather than a heavier but faster transmitter.

    Looking at the atmosphere backlit by the sun is why they chose closest approach on the dark side of Pluto. This allowed them to see the chemical makeup of the atmosphere but hindered their look at the surface.

  • Rocco

    A nice comment on sublimation which btw gives me a push to dig further into the area of sublimation.
    And an added thanks for the information about the New Horizons mission to look at the atmosphere of Pluto. Interesting stuff.

  • Edward

    In recent decades, scientists have discovered that ice has different characteristics at different temperatures and pressures. You may want to consider looking into the “phases” of ice as a nice distraction from the problems of the day.

    I remember the reasoning for the urgency of sending a probe to Pluto, back when they were proposing it.

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