New images of Pluto‘s surface have revealed an unexpected range of mountains, glacial flows, smooth plains and other landscapes that have frequently evolved over millions of years, researchers from NASA’s New Horizons mission have revealed.
Their results, published in a suit of five studies published Thursday in a special issue of the journal Science, show a complex, geologically active world 3 billion miles from Earth.
After traveling through the solar system for nine years, the New Horizons spacecraft made its closest approach to the Pluto system last July. Equipped with seven extremely sensitive scientific instruments, it took high-resolution images of the dwarf planet’s surface features, observed its five satellites, monitored its atmosphere and measured its interaction with the solar wind.
“I don’t know any other place in the entirety of the outer solar system where you see anything like this,” said New Horizons principal investigator Alan Stern. “The closest analogy is the Earth, where we see water-rich surfaces and rock-rich surfaces that are completely different.”
How the varied terrain came to be remains a mystery. Scientists suspect several processes at work, including vaporization of nitrogen, carbon monoxide and methane, into Pluto’s cold and unexpectedly compact atmosphere. Pluto also still likely has enough internal heat from its formation some 4.5 billion years ago to help maintain some of its its most prominent features.
Some icy satellites, such as Saturn’s moon Enceladus and Jupiter’s moon Europa, harbor substantial internal heat, which is generated by the powerful gravitational tug of their giant parent planets. But something else is likely happening at Pluto.
“I think we have to rethink our whole understanding of geophysics — how you keep small planets active over time,” Stern said.
Other studies looked at Pluto’s atmosphere, which is colder and more compact than the researchers expected.
The team also looked at Pluto’s primary moon, Charon. Scientists now believe Charon and Pluto’s owe their existence to a crash between Pluto and another body early in the solar system’s history. Pluto’s natural satellites were formed from the debris that was hurled into space after the crash
Thankfully, there’s still a lot of flyby data left to analyze. New Horizons, which was launched in 2006, has beamed only half of the close-encounter images and measurements back to mission control.