Pluto used to be the ninth planet from the Sun and the smallest one in the Solar System. It is also the object that launched endless arguments on its designation -- whether it is a planet or not. 

Today, Pluto is called a dwarf planet and its story is about to be revealed.

Alan Stern, a lead scientist of the New Horizons mission, has made a book deal with Picador to write a "behind the scenes" account of the mission, reports the Associated Press.

"New Horizons" is NASA's first ever mission to Pluto. Moreover, the book will be called "Chasing New Horizons: Inside Humankind's First Mission to Pluto."

David Grinspoon, a planetary scientist and author, is co-writing the book. Grinspoon's popular writing has been featured in many publication including Nature and Science.

He has been awarded the "Carl Sagan Medal for Excellence in Public Communication." His latest book is called "Lonely Planets; The Natral Philosophy of Alien Life."

"New Horizons" is the first NASA mission to venture into the Kuiper Belt, the vast region of bodies swarming beyond Neptune. Kuiper Belt is where Pluto is found, along with other dwarf planets such as MakeMake and Haumea.

Ironically, while Pluto used to be known to the Solar System as the smallest planet, BBC notes that it is considered a large object in the Kuiper Belt.

On July 14, 2015, New Horizons has flown past Pluto and completed its first era of planetary reconnaissance, Alan Stern writes in a blog post.

He mentions that July 14 held another milestone in space exploration history fifty years ago. On July 14, 1965, Mariner 4 became the first mission to reach Mars.

His team found out that Pluto is a cold planet, with its crust possibly composed of water ice. They have also discovered four previously unknown moons of the dwarf planet, namely Nix, Hydra, Styx and Kerberos. Its biggest moon is called Charon.

However, over 95& of data from the mission still hasn't reached Earth. The latest data revealed that Charon's surface includes many valleys, mountains and a system of canyons four times longer than the Grand Canyon, reports Time.

This indicates that Charon may have had a violent geological past.

"Getting all those observations back will take some 16 months and won't complete until the fall of 2016. So expect many more images and spectra and, from those, many more discoveries in the months ahead," Stern wrote.

"New Horizons is a gift that will keep on giving," he added.