Much to the amazement and delight of scientists, the latest findings about Pluto reveal it possesses hazy blue skies and numerous red colored patches of water ice exposed on the surface of a world also now known as “The Other Red Planet.”
With each passing day, significant discoveries about Pluto continue piling up higher and higher as more and more data gathered and stored from this past summer’s historic flyby by NASA’s New Horizons reaches ground stations back here on Earth.
“Blue skies–Pluto is awesome!” says Alan Stern, New Horizons principal investigator from Southwest Research Institute (SwRI), Boulder, Colorado.
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The bluish tint to Pluto’s skies were unexpectedly discovered after researchers examined the first color images of the high altitude atmospheric hazes returned by New Horizons last week that were taken by the probes Ralph/Multispectral Visible Imaging Camera (MVIC).
“Who would have expected a blue sky in the Kuiper Belt?” Stern said in a NASA statement.
During New Horizons flyby on July 14, 2015, it discovered that Pluto is the biggest object in the outer solar system and thus the ‘King of the Kuiper Belt.”
The Kuiper Belt comprises the third and outermost region of worlds in our solar system.
“It’s gorgeous!” exclaims Stern.
Moreover, the source of Pluto’s blue haze is different from Earth’s and more related to Titan, Saturn’s largest moon – currently being explored by NASA’s Cassini mission orbiting Saturn since 2004.
On Earth, the blue sky is caused by light scattering off tiny particles of nitrogen molecules. Whereas on Titan its related to soot-like particles called tholins.
Tholins are generated by a series of very complex sunlight-initiated chemical reactions between nitrogen and methane (CH4) high in the atmosphere. This eventually produces relatively small, soot-like particles of complex hydrocarbons.
“That striking blue tint tells us about the size and composition of the haze particles,” said New Horizons science team researcher Carly Howett, of SwRI, in a statement.
“A blue sky often results from scattering of sunlight by very small particles. On Earth, those particles are very tiny nitrogen molecules. On Pluto they appear to be larger — but still relatively small — soot-like particles we call tholins.”
As the tholins rain down on Pluto, they add to the widespread red surface coloring.
The Ralph instrument was also key in another discovery announced by New Horizons researchers.
Numerous small, exposed regions of water ice on Pluto’s surface were discovered by combining measurements from the Ralph MVIC spectral composition mapper and infrared spectroscopy from the Linear Etalon Imaging Spectral Array (LEISA) instrument.
The strongest signatures of water ice were found in the Virgil Fossa and Viking Terra regions berby the western edge of Pluto’s huge heart-shaped Tombaugh Regio feature – see image below.
Water ice is only found in certain zones of Pluto for reasons yet to be understood. There may also be a relationship to the tholins, that likewise is yet to be gleaned.
“I’m surprised that this water ice is so red,” says Silvia Protopapa, a science team member from the University of Maryland, College Park. “We don’t yet understand the relationship between water ice and the reddish tholin colorants on Pluto’s surface.”
As of today, New Horizons remains healthy and is over 3.1 billion miles (5 billion kilometers) from Earth.
The team hopes to fire up the thrusters later this fall to propel the spacecraft toward a second Kuiper Belt Object (KBO) in 2019 tentativley named PT1, for Potential Target 1. It is much smaller than Pluto and was recently selected based on images taken by NASA’s Hubble Space Telescope.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.