Pluto: Stranger Than Expected

Ice mountains near the equator of Pluto. These mountains are 3,500 meters high and only 100 million years old.

Ice mountains near the equator of Pluto. These mountains are 3,500 meters high and only 100 million years old.

We have learned again this week, with the fleeting passage of the New Horizons probe past Pluto, that nature is stranger than fiction, better really, with more surprises, plot twists, and interesting imagery than the most adept imaginations can conjure. The data is coming in slowly from Pluto, and we’ve received just a few images of the many yet to come. But here’s what we know from New Horizons so far…

  • On July 14, 2015, New Horizons survived its inbound flight to Pluto and passed within 12,500 km of the surface of the dwarf planet moving at a speed of 50,000 km/hr. As it passed, it travelled the diameter of Pluto in just 3 minutes and collected data and images at a rapid rate
  • The craft imaged Pluto in detail as it passed and found the planet to have a surface with large dark areas and light areas next to each other, so Pluto has an exterior unlike the far more uniform surfaces of Mercury, Ceres, or Europa, for example. The different coloring may be a result of frozen patches of methane and nitrogen that reflect different proportions of sunlight
Pluto in high resolution captured on July 11, 2015 by New Horizons

Pluto in high resolution captured on July 11, 2015 by New Horizons

  • Pluto has regained its status as the largest dwarf planet, if not the most massive. Precise measurements show Pluto is 2,370 km in diameter, slightly larger than the dwarf planet Eris, which was for a time thought to span a larger diameter than Pluto. However, Eris is still some 25% more massive than Pluto and therefore significantly denser
  • Pluto has a tenuous atmosphere made of nitrogen gas. The dwarf planet does not however, have enough gravity to keep the nitrogen gas from escaping into space. So scientists have concluded, at least so far, that Pluto must be replenishing its atmosphere from within. The search is on for plumes of fresh nitrogen gas from below the surface
  • Pluto’s surface has very few craters which suggests, at least at first pass, that the surface is shockingly young, less than 100 million years old That’s a surprise for such a small body that was not expected to have geological activity. Instead of an ancient, fossilized world, astronomers have found a world that appears to renew its outer layer perhaps through gas that’s ejected from the interior and which freezes over the surface
  • The first close-up image of Pluto revealed ice mountains some 3,500 meters high near the equator. Again, these immense mountains must be quite young and formed during the reign of the dinosaurs on Earth
  • Charon, Pluto’s largest moon, is also a strange little world of chasms and craters, as well as a dark region near its north pole. The most pronounced chasm on Charon is longer and deeper than Earth’s Grand Canyon, and the most prominent crater is nearly 100 kilometres across, as large as the crater Copernicus on our Moon.
Charon, Pluto's largest moon

Charon, Pluto’s largest moon

More data is coming in, and it will come in at higher resolution than what we’ve seen so far. There’s no fiber optic cable to Pluto so this will take time. Much of the data will continue to come in through August and September which means, one NASA scientist said, “This is a mission of delayed gratification”.

Some of the ashes of Clyde Tombaugh, who discovered Pluto in 1930 after an arduous search, are aboard New Horizons. I suspect Clyde would be impressed by the results streaming in from Pluto this week. He, more than most, knew well that you never know what you might find until you look.


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