NASA has identified evidence of ice volcanoes present on the surface of the dwarf planet Pluto. The news comes as New Horizon's team discusses new scientific discoveries made by the spacecraft during its July flyby, at the 47th Annual Meeting of the Division for Planetary Sciences (DPS) of the American Astronomical Society, in Maryland.
Simply put, New Horizons has transformed our understanding of Pluto. Where before our best view was a pixilated Hubble image, we are now presented with a treasure trove of high-resolution images detailing a celestial body that boasts a stunningly diverse range of geological processes and environments.
The New Horizons team combined multiple images of Pluto's surface to create a 3D map of the suspected cryovolcanoes, which have been unofficially named Wright Mons and Piccard Mons. Wright Mons, located to the south of Sputnik Planum, towers two miles (3.2 km) above the surrounding landscape and spans around 100 miles (160 km), whilst the taller Piccard Mons stretches a full three miles (4.8 km) up toward the dwarf planet's tenuous atmosphere.
A cryovolcano differs significantly from volcanoes located on planets closer to the Sun, such as on Earth or Venus, which are known to erupt with molten rock and ash. A cryovolcano is the result of volcanic processes that take place on more distant icy planets and moons. It is theorized that an eruption from Wright Mons or Piccard Mons would eject vast quantities of a slurry-like cocktail of water ice, nitrogen, ammonia and methane.
3D topographical map of Pluto's suspected cryovolcanoes – blue indicates recessed terrain, with brown representing higher elevation, and green representing intermediate heights
"These are big mountains with a large hole in their summit, and on Earth that generally means one thing – a volcano," states Oliver White, New Horizons postdoctoral researcher with NASA’s Ames Research Center, Moffett Field, California. "If they are volcanic, then the summit depression would likely have formed via collapse as material is erupted from underneath. The strange hummocky texture of the mountain flanks may represent volcanic flows of some sort that have travelled down from the summit region and onto the plains beyond, but why they are hummocky, and what they are made of, we don't yet know."
Should further studies corroborate the theory that Wright Mons and Piccard Mons are indeed cryovolcanoes, the discovery will have significant implications on current models regarding the dwarf planet's geological and atmospheric evolution.
Another study counted the number, size and spread of asteroid impacts across Pluto's surface in order to determine the relative ages of the diverse geological regions. Areas with heavier cratering are considered to be older than surface regions formed more recently.
It was discovered that some of the most heavily cratered, and therefore most ancient regions are estimated to be roughly four billion years old – dating back to the early solar system. Conversely, other regions, such as Sputnik Planum, exhibit no signs of asteroid impact whatsoever, meaning that they must have been formed some time in the last 10 million years.
An analysis of crater distribution also led to the discovery of so called "middle-aged" surface areas, leading NASA scientists to the conclusion that Pluto has been geologically active for much of its existence.
The impact map may also lead to a rethink on current models regarding the make-up of the Kuiper belt. The prevalence of large craters on Pluto compared to the relatively rare smaller craters is inconsistent with models that suggest that Kuiper belt bodies grew through an amalgamation process, suggesting instead that the rocky constituents of the belt, which may be tens of miles in length, were instead simply born large.
Yet another study highlights the unusual nature of Pluto's moons. Based on New Horizons' observations, it appears that the gravitational influence of Pluto's largest moon, Charon, is preventing the dwarf planet's other wards from taking on traditional satellite characteristics.
Most moons orbiting planetary bodies in our solar system are tidally locked, meaning that they only ever present one face to their parent. The disturbance created by Charon's presence has led to Pluto's smaller moon's spinning wildly out of sync, with the dwarf planet's most distant moon, Hydra, rotating 89 times in the period it takes to complete a single orbit.
New Horizons will continue to send back images and data as it progresses through its year long information transfer, shedding light on ever more geological wonders at work on the strange dwarf planet, and her moons.