Pluto's surface surprisingly full of mountains and lacking craters

Scientists for NASA's New Horizons mission on Wednesday shared some tantalizing early discoveries about Pluto - and the first piece of what will soon be a stunning photographic mosaic of the dwarf planet.

The most detailed photo of Pluto ever seen captures a tiny piece of its surface, revealing a terrain with an unexpected lack of craters and an abundance of mountains. Both finds are surprising: Pluto and the other objects in the Kuiper Belt are as old as the solar system, and that means 4.6 billion years' worth of getting pummeled by comets.

The fact that Pluto seems to be so craterless suggests that its surface is very young, said the scientists at the briefing at the Johns Hopkins University Applied Physics Laboratory in Columbia, Maryland. In other words, there's been geological activity recently enough to smooth out the surface quite a bit.

The many mountains pictured - some as high as 11,000 feet - are probably less than 100 million years old.

The early information on Pluto also is upending what scientists thought they knew about geology on icy worlds. On other ones, geologic activity is powered by heat created from the gravitational pull of a much larger nearby body. That isn't true in Pluto's case; something else must make active geology possible.

The team also released a new image of Charon, Pluto's largest moon, which shares a strange orbital relationship with its host. It's half of Pluto's size, which is the largest moon-to-host ratio in the solar system, and the pair orbit a common point together like two ice skaters holding hands and spinning.

According to the latest data on Charon, the pair may be even more closely linked than scientists had thought. At another briefing on Wednesday, the team suggested that the dark patch on top of Charon — nicknamed Mordor — could come from ice borrowed from Pluto.

In theory, Charon could be temporarily trapping some of Pluto's atmosphere, which has a tendency to escape into space.

"We've been arguing," said William Grundy, of the New Horizons composition team. "The counterproposal is that [the dark spot] is just an impact basin. That's an alternative explanation."

At Pluto's temperatures, ice behaves like rock - so it's possible that the towering mountains seen on Pluto are made of ice. But knowing what they're made of won't solve the mystery of how they got there - or how the craters that must have been on Pluto's surface smoothed themselves out without the warmth of a larger planet's tidal pull.

Scientists probably won't have all the answers about Pluto even after New Horizons finishes its 16-month data dump. And the team is already pushing for funding for an extended mission, which would allow the spacecraft to visit another icy body in the mysterious Kuiper Belt.

The belt is thought to have trillions of comets and perhaps hundreds of thousands of larger bodies, and the New Horizons team has selected a few potential targets for a second flyby. If the group gets funding, it could do some controlled burns of the spacecraft's propulsion system to turn it in the right direction, sending it to a world even more mysterious than Pluto.