With the resumption of image and data transmissions from New Horizons, at the start of September, they had indicated that Fridays would henceforth, and for the course of the next 12 months, be known as Pluto Friday, the day on which the latest raw images from the mission to that distant tiny world and its companions would be released.
However, the first set of images came a little sooner than advertised: on Thursday, September 10th, and they continue to show two tiny worlds which continue to astound and have planetary scientists rethinking much about their understanding of dwarf planets.
“Pluto is showing us a diversity of landforms and complexity of process that rival anything we’ve seen in the solar system,” New Horizons’ principal investigator Alan Stern, from the Southwest Research Institute in Colorado, said in a statement. “If an artist had painted this Pluto before our flyby, I probably would have called it over the top — but that’s what is actually there.”
The images render details as small as 400 metres / 440 yards per pixel on the surface of Pluto, and reveal features that have scientists agog with excitement; so much so that at a NASA press conference, the images were summarised thus, “it’s complicated!”
In them, we can see a rich complexity of features: nitrogen ice flows which have apparently oozed (and might still be slowly oozing) out of mountain ranges and across broad plains; mountain ranges which are themselves reminiscent of chaotic regions on Mars and Jupiter’s Europa; complex valley systems which might have been carved by the action of material flowing across the planet; and even – perhaps most curiously of all – what seem to be wind-blown fields of dunes.
What is also particularly striking about these images of Pluto is the way that they reveal some of the oldest (geologically speaking) regions yet seen on the planet sitting right alongside what are the youngest locations on the planet, adding further emphasis to the idea that Pluto has been, and might still be, an active world.
But what about those dunes mentioned above? If they are indeed what the images released on September 10th suggest, Pluto has once again served up a surprise.
“Seeing dunes on Pluto, if that is what they are would be completely wild!” William McKinnon from the mission’s Geology, Geophysics and Imaging (GGI) team, said, “because Pluto’s atmosphere today is so thin. So either Pluto had a thicker atmosphere in the past, or some process we haven’t figured out is at work. It’s a head-scratcher!”
More is also being discovered about Pluto’s atmosphere, which is also proving to be a lot more complex than had originally been thought, having many more layers within its thin haze than had been thought. However, these layers of haze have allowed the science team to glimpse surface features which might otherwise have remained unseen as sunlight caught by the haze over the terminator – the divide between the day and night sides of the planet – cast a soft glow over part of Pluto’s night side. When enhanced through careful processing, this glow could be used to reveal what lay below.