On this day 5 years ago, NASA’s New Horizons spacecraft gave us a whole new view on Pluto. The spacecraft spent 9 and a half years swinging past Jupiter and heading to the edge of the solar system, before coming within 7,800 km of the distant dwarf planet. Prior to this, we didn’t know much about it. Discovered in 1930, it was little more than a blurry dot until New Horizons’ first look at Pluto sent back the very first detailed images of the rocky world.
New Horizons’ Journey
The New Horizons mission is in it for the long haul. Launched in 2006, it was sent out into the vacuum of space to investigate Pluto and the mysterious Kuiper Belt. This is a region of space that exists beyond Neptune. It contains small rocky bodies and asteroids, as well as a few ice dwarf planets like Pluto.
Before it could do any of this, it needed a way to get there. Travelling to the outer solar system isn’t quite as simple as pointing a rocket in the right direction! Other planets and bodies in our solar system could interfere, using their gravity to pull the spacecraft off course. Luckily, scientists have a pretty good idea of how gravity is distributed in the solar system. As the largest planet, Jupiter can cause the biggest problems. But it can also help the most! After launch, New Horizons first set out for Jupiter, where it would use the goliath’s gravity to boost it towards Pluto. It even transmitted some data on the planet for good measure!
But on its way to Pluto, disaster struck. The spacecraft went silent for 90 minutes on July 4th, 2015, less than 2 weeks before reaching the dwarf planet. Thankfully, the mission team worked quickly to find the problem and get it back up and running. An overloaded main computer was no match for their talents!
A Surprising New World
Although nothing had ever been this close to Pluto before, scientists were still blown away by what they found. The world’s terrain proved to be diverse, with flat plains of water ice and cryovolcanoes sharing a body just 2,377 km wide. It even contained a huge heart-shaped plain, making the surface of Pluto an instantly recognisable sight today. This plain was named the Tombaugh Regio, after the discoverer of Pluto, Clyde Tombaugh.
But the most interesting find was that the left lobe of the Tombaugh Regio was suspiciously crater-free. This indicated that it had been resurfaced relatively recently, leading to the conclusion that Pluto is geologically active. This was a huge discovery, and to this day scientists still don’t know what powers this activity. One theory is that latent heat is released by a slowly freezing ocean beneath Pluto’s surface. This even leads to the possibility of life on this remote world!
New Horizons’ data has contributed to countless revelations about this far away body. Scientists around the world are still working on the data, hoping to glean some new secrets about Pluto. But the spacecraft didn’t stop there. It continues its journey out past Pluto’s orbit.
In 2019, New Horizons performed another flyby, this time of Arrokoth, a 35 km long object. This gave us a view of a very different world making its home within the Kuiper Belt. The spacecraft even has about one-eighth of a tank of fuel left, so could go on to do one more flyby in its lifetime. For now, scientists are patiently waiting for a suitable candidate to be found.
We know far more about Pluto now then we did for years, but we’re not finished yet! The breadth of information collected by New Horizons gives rise to support for new missions to the dwarf planet. In the future there might even be spacecraft sent to orbit Pluto, and see how it changes over time. But for the time being, there are still plenty of discoveries waiting to be made, and all from the work of one intrepid spacecraft!