The image above was among the data that the New Horizons probe is still streaming back to Earth, after its flyby of Pluto. To a lot of scientists working on interpreting the data it looked “for all the world…like a former lake,” the project’s principle investigator told reporters.
This blob on Pluto’s surface is flat, featureless and smooth, ScienceAlert writes—in other words, it looks a lot like a “pond-like feature” where a liquid froze all at one level. But how could cold Pluto have a lake at all? Currently its surface temperature clock in at a not-exactly-liquid-friendly -380 degrees F.
The New Horizons teams has come up with a model showing it’s possible: as Pluto moves in its 248 year orbit around the sun, its axis tilts, changing the air pressure on the surface dramatically. That change in pressure changes the temperature (they’re proportionately related, as you may remember from physics class), and the end result is that some of the vast plains of frozen nitrogen currently on Pluto could have once been liquid.
Given all the factors involved, this would have been approximately 800,000 years ago. But theoretically it could happen again! Whether humans happen to be around to observe it is a whole other question.
Bonus finds: An incredibly bright galaxy
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