The first images from New Horizons' history-making flyby of Pluto revealed a moon-cluttered system that's more complex than anyone knew.
Business Insider asked a few astronomers for their first impressions of the new high-resolution photos.
It immediately became clear that three major features stand out, and scientists can't explain any of them.
1. Those crazy 11,000-feet-tall mountains, which might be made of ice.
"It's mind-blowing that those mountains are on Pluto," Phil Metzger, a planetary physicist who recently retired from NASA’s Kennedy Space Center, told Business Insider.
The New Horizons team was shocked to0. They expected to Pluto to be fairly uniform and featureless.
"The distinction between ice and rock is arbitrary," Metzger said. "Ice can have all the mechanical properties of rock when it's cold enough."
Still, we have no idea what's creating these "massive peaks with no obvious dynamical process to produce them," Maria Zuber, a geophysicist at MIT, told Business Insider.
They could be geysers or cryovolcanoes, or caused by them, New Horizons principle investigator Alan Stern hinted during a NASA press conference on Wednesday.
We'll need more detailed information from New Horizons to figure that out, but it could take more than a year to get all of the flyby images and scientific readings beamed down to Earth.
2. That band of smooth, crater-free surface.
Scientists estimate that smooth patch on Pluto is only about 100 million years old, as opposed to our 4.5-billion-year-old solar system.
And that young, smooth swatch has a really important implication: It could mean that Pluto has an active sub-surface that keeps resurfacing and smoothing over the top layer, Zuber said.
"Pluto has an active interior, for reasons that are not at all clear," she said. "When ice-rich planetary bodies show evidence of resurfacing the interior it is usually tidal forces, but there is not a large nearby planetary body to raise tides. It’s an extraordinary scientific mystery."
3. That heart that everyone keeps turning into a meme.
But the most bizarre thing is still the giant heart on Pluto, according to Mike Brown, an astronomer who calls himself "Pluto killer" on twitter for his role in the planet's demotion.
New Horizons scientists are pretty sure it's a heart-shaped streak caused by snow, but not the kind we're used to here on Earth. It's probably methane snow.
But the most intriguing thing about the heart is its location on Pluto, Brown said.
"[The heart] is eye catching, for sure, but more importantly it is a giant ice patch right at the equator which is supposed to be the warmest part," Brown said. "I'm still trying to wrap my head around what any of it might mean."
It's the combination of these three things that makes Pluto unlike any other body we've explored.
"It's going to send a lot of scientists back to the drawing board," Stern said during a press conference this week.
The bottom line, says Victor Baker, a professor of planetary sciences and geosciences at the University of Arizona, is that there's some crazy-complicated geology happening on Pluto that we don't fully understand yet.
"This kind of complexity may puzzle some planetary scientists, but we geologists love the complexity with all the mysterious details," Baker told Business Insider. "Geologists are going to have lot of fun explaining what has gone on with Pluto."
We can't wait for the next influx of data from New Horizons, which is supposed to arrive Friday.
