It’s a mission that cost $650 million to mount, took 5 years of planning and building prior to spending 9.5 years in space as one of the fastest man-made objects yet built (and the fastest ever at launch); it has travelled some 4.76 billion kilometres to reach its destination, swinging by and studying Jupiter (the first time we’ve done so close-up in over decade) in the process. All this for a close encounter which, due to the speed of the vehicle, could be measured in a mere hours.
But what an encounter!
I’m of course referring to NASA’s New Horizons mission which, on July 14th, 2015, after all of the above, flashed by the Pluto-Charon system precisely on target and just 72 seconds ahead of it’s predicted arrival time of 11:49:59 UTC at its closest point to Pluto.
Obviously, the overall encounter has been going on for some time now, as I previewed in my Space Sunday report of July 12th: what NASA called the “distant encounter phase” started in January 2015, and even now, as New Horizons heads away from Pluto and Charon, observations are still being made. But the mission has always been about the hours immediately either side of that point of closest approach, when New Horizons flashed by Pluto at a speed relative to the planet of 13.77 km/s (8.56 miles per second).
The close approach wasn’t something that could be followed in real-time, the time delay in transmissions from the probe to Earth being some 4.5 hours. This being the case, NASA kept people informed with images and information recorded in the hours leading-up to the period of closest approach, such as a stunning image of Pluto captured by New Horizon’s LORRI and Ralph instruments on July 13th. Since then, they’ve been releasing a steady stream of the initial images that have been returned by the probe.
Pluto also appears to be an active planet – more so than had been imagined – with distinct compositional difference across its surface, making understanding of some of its characteristics difficult, so it is going to be some time before a range of questions relating to Pluto’s formation, development, etc., are liable to be answered, as many of them are going to have to wait for the arrival of very high-resolution lossless images from the probe, some of may now be received until well into next year (transmission of all the data recorded by New Horizons will take some 16 months).
In particular, New Horizons focused on a bright region positioned towards the centre of the of Pluto’s sunlit side and initially dubbed “Pluto’s Heart” due to its shape (seen most clearly in the image above left). Now informally christened “Tombaugh Regio”, after Pluto’s discoverer, Clyde Tombaugh, the region has been of interest to the science team due to its apparent “youthful” appearance: it is relatively crater-free, suggesting the surface has undergone significant re-working compared to the surface features around it, which are far more heavily cratered.
The region is home to a series of intriguing features, including the “Norgay Montes”, named after Tenzing Norgay, Edmund Hillary’s companion on the 1953 ascent of Mount Everest. This is a range of mountains rising some 3,300 metres (10,000 feet) above the surrounding plains, and which are estimated to be around 100 million years old, making them one of the youngest surface features seen in the solar system (younger than the Appalachian Mountains in North America, for example). There are believed to be a exposed region of Pluto’s bedrock, itself likely to be heavily comprised of water ice.