Scientists at the nearby Johns Hopkins Applied Physics Laboratory received their first images on Wednesday from the closest approach of the New Horizons spacecraft at Pluto. New Horizons swept to within 7,700 miles (12,391 kilometers) of Pluto during its flyby.

And Pluto, long considered the farthest planet from the Sun before it was reclassified as a dwarf planet in 2006, has never before been explored.

Although methane and nitrogen ice covers much of the surface of Pluto, these materials are not strong enough to build the mountains. Activity on other icy bodies is powered by gravitational pulls from nearby larger objects, which Pluto does not have.

The photos collected on the NASA probe’s flyby of Pluto are only a fraction of whats to come over the next six months as New Horizons ‘ transmits as it flies’ deeper into the Kuiper Belt.

The towering mountains of Pluto are such a puzzle, they said.

Another surprise was Pluto’s primary moon, Charon, which was believed to be geologically dead.

A new close-up of a small region on Pluto’s surface also reveals towering ice mountains, up to 11,000 feet high. Few craters are visible in the image, which shows an area of about 240 miles from top to bottom.

New Horizons has finally nailed the basic physical properties of Hydra”, Hal Weaver, New Horizons Project Scientist and LORRI science operations lead, said in a statement.

In the latest batch of images beamed back from the spacecraft, NASA has identified an unusual depression running across Charon, one of Pluto’s moons, slashing across the rock with a length of around 240 miles and complete with a central peak. “This means they could be equally diverse and be equally wonderful if we ever get a spacecraft out there to see them close up”. It’s smaller than our own moon, and it orbits at an angle relative to the plane of the solar system. This indicates that Charon’s crust has numerous fractures which might have been caused due to internal geological processes.

It is the fastest spacecraft ever launched – hurtling through the Pluto system at more than 30,000 miles per hour.

New images of Pluto are expected to be released Friday.

New Horizons Flight Controllers cheered and hugged each other as the probe re-established contact with mission headquarters.