The mysteriously lovely Pluto puzzles scientists

Launched in January 2006, New Horizons flew past Pluto on July 14, passing within 7,770 miles of the dwarf planet’s frigid surface, studying the world with a sophisticated suite of instruments as it approached and departed.

Ever since then, New Horizons has been streaming back the data it collected during its flyby of the Pluto system.

Not only does Pluto’s surface show a surprising variety of features – from weirdly smooth plains to ridge-like mountains – but that surface is actively changing, as described by Stern and others from the New Horizons team in a paper published Thursday in the journal Science.

Pluto’s diverse surface geology and long-term activity also raise fundamental questions about how it has remained active many billions of years after its formation. The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, designed, built, and operates the New Horizons spacecraft and manages the mission for NASA’s Science Mission Directorate.

This “tells us that the surface has very different reflectivity in different places and that there is a much higher range of reflectivities on Pluto than essentially any other body in the solar system”, Stern told me. The spacecraft was able to capture a number of remote sensing and in situ dimensions of Pluto and its five-moon system.

Pluto’s atmosphere contains volatile chemicals such as methane, nitrogen and carbon monoxide. It includes details as seemingly mundane as Pluto’s size – 2,374 kilometres across, plus or minus 8 kilometres – that other scientists can use to refine their understanding of properties such as heat flow within the dwarf planet.

Even now, three months after New Horizons’ close encounter, scientists are just beginning to get a handle on what’s going on with Pluto and it’s large, equally intriguing moon Charon.

The scientific data sent back suggests that Pluto has one of the most varied landscapes in the Solar System.

The New Horizons mission suggested Pluto might be larger than Eris, so a case could be made to reinstate the former planet.

Pluto shows no significant flattening, at the poles, indicating no evidence “of an early, high-spin period after Pluto-Charon binary formation”, Stern concludes, “presumably because it was warm and deformable during or after tidal spindown”. There is also a few information about two smaller moons, Nix and Hydra, which were both significantly brighter than scientists expected-another Plutonian puzzle.

Many of these planetary processes are also observed on Charon, demonstrating that recent geological activity is not unusual in the Kuiper Belt-a massive circle of planetoids and debris circling the solar system.

The source of Pluto’s reshaping, evidenced in its plains of frozen ices and towering ice mountains, is a mystery awaiting solution. “The nitrogen (N2), carbon monoxide (CO), and methane (CH4) ices that were known from ground-based spectroscopy to dominate Pluto’s visible surface would collapse exceptionally rapidly because they are weak… solids”.

The Science paper is titled ‘The Pluto System: “Initial Results From Its Exploration by New Horizons” and has 151 co-authors, including Stern.

The Sputnik Planum, in particular its smoothness, is also revealing. We now know the sizes of Pluto and Charon much more accurately, and it turns out that they share similar densities and so may be composed of the same stuff.

New Horizons gave us more than a look at the surface of Pluto. Through this analysis, they found out that there are different volatile ices on the planet, each corresponding to a different region.

The atmosphere of Pluto is 100,000 times thinner than that on Earth, but when New Horizons sped past and looked back towards the sun, it captured images of a blue haze circling the world. And this knowledge should shed light on the long-ago giant collision that researchers think formed the Pluto-Charon system. A new study has revealed that the dwarf planet in the Kuiper belt is an unexpectedly complex and idiosyncratic planet.