The more we find out about Pluto, the more perplexing it seems. For several weeks after its July 14 fly-by, NASA’s probe New Horizons was too busy doing science to transmit data to Earth. During that time we had to content ourselves with the few “taster” images that were beamed back immediately after it passed Pluto.
However the probe has now begun the year-long process of transmitting its vast haul of fly-by data, including images that are crisper and more reliable because they preserve original details that we couldn’t see in the compressed versions. A selection of new images is released every Thursday—with the latest revealing Pluto’s haze layers in stunning detail.
Crazy Haze
The picture above is my favourite. It was captured just 15 minutes after closest approach, looking back sunwards across part of the southern edge of the bright area informally known as Tombaugh Regio.
The water-ice mountains adjoining and projecting up through it are wonderfully shadowed, and look at the incredibly complex haze layers that you can see above the distant horizon. These are probably a product of the solar ultraviolet light stripping hydrogen from molecules of methane, which then link together to form long chains of tar-like substances called tholins. These form tiny particles, and those that settle to the ground help to give it a reddish stain, but why there are so many layers in the atmosphere, we don’t know.
Below is a spectacular simulated view (compiled from several individual images) showing the Tombaugh Regio area to the north and the dark, heavily-cratered terrain to its south. These craters are prominent because of their bright rims, which could be nitrogen frost. What catches my attention in particular on this image are the curved and branching fractures that sweep across the terrain in the lower left and slice through several of the smaller craters, providing evidence of an episode of geological activity, maybe even within the past billion years.
