Water ice mountains 11,000 feet tall. No impact craters. The provocative possibility that Pluto's surface is much, much younger than we thought—and that the planet is still geologically active. So too is Charon, one of its four moons.
These are just a few of the conclusions scientists on the New Horizons mission are drawing from the first closeup images of Pluto and two of its moons. After a journey of 9.5 years and 3 billion miles, yesterday NASA’s New Horizons spacecraft got within 7800 miles of the surface, the closest encounter with Pluto the human race has ever had. Its scientific payload went into high gear as the probe flew by at more than 30,000 miles an hour, taking in reams of data via seven high-tech instruments.
The probe was out of contact with mission headquarters for 13 hours so it could focus on gathering rather than transmitting data. When it reestablished contact last night at 8:52:37 p.m. ET, there was jubilation at the Johns Hopkins University's Applied Physics Laboratory (APL), mission headquarters. All the systems reported back as normal. "We have a healthy spacecraft," said Alice Bowman, mission operations manager.
Now we're seeing the first images from that superfast data grab. The new black-and-white image of Pluto shows a mountain range made of water ice, with peaks jutting as high as the Rocky Mountains, the team says. Here's a close up:
"The most striking thing is that we haven't found a single impact crater, which means this is a very young surface—less than 100 million years old," project scientist John Spencer said in a NASA press briefing. Collisions and the resulting impact craters were common in the volatile early years of our solar system's formation.
"It's clear that Pluto has remarkably varied terrain, and that the different colorations and textures of the large surface features point to diverse geological processes—surprising, perhaps, in a planet with so little external energy coming from the sun," Gettysburg College astronomer and professor emeritus Lawrence Marschall, co-author of Pluto Confidential, tells mental_floss. "The strong tidal interaction of Charon and Pluto may be responsible for the geological diversity you see. The very high mountains are particularly impressive."
We also spoke to the man responsible for Pluto's demotion to a dwarf planet: Mike Brown, the CalTech planetary astronomer whose discovery in 2005 of the planet Eris led to Pluto's reclassification as a dwarf planet. Because Eris was thought to be bigger than Pluto, some floated the idea that Eris be considered the 10th planet in the solar system. Instead, Pluto was "demoted," angering schoolchildren everywhere. (Eris, too, is considered a dwarf planet.)
Brown calls the ice mountains on Pluto "very strange," but he doubts they are as young as the New Horizons team thinks. "It seems to me that they could be old mountains poking through some young icy terrain," he says. "The footprint of the mountains is so small that you'd have a hard time finding a crater on one even if it were there."
Brown's Twitter handle may be @plutokiller, but he was struck by the image of Charon. Here it is:
"My first thought upon opening up the Charon image was: 'Where are all of the impact craters?'" says Brown. Like Pluto, Charon's surface seems to be relatively baby-faced among objects in the solar system. "Pretty cool: we've known for 15 years that there would be ancient ice floes on the surface, but I would have thought that they were ancient enough that they were still covered in craters. Seems like the ice floes were more recent."
We'll have more details about the discoveries coming soon from contributor David Brown, who spoke to scientists at the NASA press briefing. Stay tuned.
In the meantime, consider that New Horizons is already more than a million miles past Pluto. It now heads into the Kuiper Belt, a gigantic zone of icy bodies and mysterious small objects orbiting beyond Neptune, where it will explore the origins of the outer solar system and how planet-satellite systems evolve. Because it's so energy efficient, New Horizons could, in theory, send us data for the next 30 years.