Blue skies and water ice may sound like things you’d find in a cool, picturesque vacation spot on Earth. Would you believe these were found on Pluto?
The US National Aeronautics and Space Administration (NASA) said its New Horizons spacecraft sent home images of Pluto’s haze layer showing its blue color.
Even if the sight was literally out of this world, it drew admiration from New Horizon’s handlers.
“Who would have expected a blue sky in the Kuiper Belt? It’s gorgeous,” an October 8 article on NASA’s website quoted Alan Stern, New Horizons principal investigator from Southwest Research Institute (SwRI), Boulder, Colorado, as saying.
As of Oct. 9, NASA said the New Horizons spacecraft was 3.1 billion miles (five billion kilometers) from Earth.
NASA said the high-altitude haze was “thought to be similar in nature to that seen at Saturn’s moon Titan.”
It said the source of both hazes likely involved sunlight-initiated chemical reactions of nitrogen and methane, “leading to relatively small, soot-like particles (called tholins) that grow as they settle toward the surface.”
While NASA theorizes the haze particles are likely gray or red, they scatter blue light.
Carly Howett, also of SwRI, said the blue tint may tell something about the size and composition of the haze particles.
“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,” Howett said.
Scientists said it was possible the tholin particles form high in the atmosphere.
There, the ultraviolet sunlight breaks apart and ionizes nitrogen and methane molecules and lets them react to form more complex negatively and positively charged ions.
New Horizons also found what NASA described as “small, exposed regions of water ice” on Pluto.
“The strongest signatures of water ice occur along Virgil Fossa, just west of Elliot crater on the left side of the inset image, and also in Viking Terra near the top of the frame. A major outcrop also occurs in Baré Montes towards the right of the image, along with numerous much smaller outcrops, mostly associated with impact craters and valleys between mountains,” NASA said.
“Large expanses of Pluto don’t show exposed water ice because it’s apparently masked by other, more volatile ices across most of the planet. Understanding why water appears exactly where it does, and not in other places, is a challenge that we are digging into,” said SwRI science team member Jason Cook.
However, the red color of the water ice has intrigued researchers.
“I’m surprised that this water ice is so red. We don’t yet understand the relationship between water ice and the reddish tholin colorants on Pluto’s surface,” said science team member Silvia Protopapa.