The Register's resident space boffin: All you need to know about the Pluto mission

Meeting a cold dwarf hasn't put off NASA one bit

Dwarf planet or not, every schoolchild still learns the name "Pluto" as the ninth and final Sun-orbiting body alongside the eight undisputed planets - and now a spacecraft of the human race has finally visited the remote iceworld.

From the very first data that reached the ground, the colossal effort was clearly worthwhile, revealing fascinating landscapes on Pluto and its moons that will rewrite the textbooks on the outer Solar System, and the conditions under which all planets formed 4.5 billion years ago.

Pluto could have been explored earlier: the Voyager 1 spacecraft had an opportunity to travel there from Saturn in the 1980s, but the allure of Saturn’s large moon Titan meant it sent there instead, so the risky trip to Pluto wasn’t undertaken.

In the years that followed, a group of planetary scientists pushed hard for a Pluto mission, with a few false starts, but the New Horizons team, led by Alan Stern of the Southwest Research Institute in Boulder, Colorado, finally achieved the goal with a compact, efficient craft that makes the absolute most of the technology available.

The high quality of the data and the smoothness of the encounter made travelling to Pluto look easy. It isn’t at all; almost everything works against achieving it.

Pluto’s huge distance from the Sun makes solar power useless, so expensive plutonium is needed for the 200 watts of power the spacecraft needs. The journey also needs to be long, which also adds to the costs. Finally, communicating reliably over almost unimaginably large distances, 30 times further away than the Sun, presents a challenge in itself.

Pluto

The eighth dwarf ... the latest (and probably last) snap of Pluto from New Horizons

Finding a balance between speed and cost largely defines a planetary mission. In short, the bigger the spacecraft and the faster you want it to travel, the bigger the rocket you need and the more expensive it is to launch.


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