Ice mountains as tall as the Rockies loom high above Pluto’s surface. They are made of water so cold as to be like rock, and they rise out of a surface of frozen methane and nitrogen. About every 150 hours, a brilliant star rises from behind the peaks. The star is no larger than a dot—not really bigger than any pinprick in the sky—but it shines with the brightness of tens of thousands of full moons.
Good morning, Pluto.
* * *
On Wednesday, NASA scientists announced the very first findings captured by the agency’s New Horizons probe. The spacecraft completed a gravitational dance with the tiny world and its moon, Charon, on Tuesday morning, but it was so occupied with observing the two orbs that it only began beaming back the very first and most compressed images hours later.
NASA released two historic new images. The first is the highest-resolution photo of Charon ever, capturing the full disk of the moon. The second is a close-up on Pluto’s surface. Both were full of surprises: It was the kind of press conference where giddy scientists chuckle and repeat, “I don’t know” over and over again.
Both images were also very, very exciting. One even suggests a new understanding of how geology might work on the universe’s many small, icy objects.
The first image reveals that Charon has some but not many craters. This is perplexing, because scientists would expect to see many on its surface. (Think about how many there are on Earth’s own, much larger moon.) The lack of them suggests that evidence of previous asteroid collisions has been erased by changes on the moon’s surface—by, in other words, geological activity.
The findings on Pluto were more surprising. The image was taken by LORRI, the high-resolution imager aboard New Horizons, and it captured a swatch of territory hundreds of miles wide.
surface captures terrain near
its south. The new image in full is
at the top of this post. (NASA)
(For reference, that patch includes some of the bottom of the enormous heart-shaped marking on the planet’s surface that was first observed on Tuesday. NASA has informally dubbed the heart “the Tombaugh Reggio,” after the astronomer Clyde Tombaugh, who discovered the dwarf planet in 1930.)
There were zero craters in the newly observed region. Again, scientists would expect to see many of them—the complete lack indicates that Pluto is almost certainly geologically active. And that throws entire ideas of how space rocks work into question.
Pluto is the first small, icy world that humankind has closely observed that isn’t orbiting a much larger planet, like Neptune or Saturn. Moons attached to a large planet might be subject to tidal heating, a process in which the force of the giant’s gravity deforms and heats the smaller one. Triton, Neptune’s largest moon, is geologically active—it has volcanoes and surface change—and scientists hypothesized that the giant blue planet might be stirring up most of that energy.