It may be July, but it’s feeling a lot like Christmas for the astronomers at Lowell Observatory. As NASA’s New Horizons spacecraft zooms ever-closer to Pluto, it is beginning to send back images of the dwarf planet that make even these seasoned scientists’ eyes go wide with excitement.
“Like a kid in the candy shop,” said Jeff Hall, director at Lowell Observatory, of these final days before New Horizons makes its closest pass at Pluto July 14.
Surface variations and more distinct colors are coming into view as new images and data stream in each day.
“Every day makes the previous day obsolete,” said Gerard van Belle an astronomer at Lowell. "Everything we thought, even yesterday, was wrong."
And unlike previous planet flyby missions, images from the spacecraft are now almost immediately put up online for everyone to see. No longer are media gatekeepers deciding what the public sees, it's all accessible to anyone who wants to see it, van Belle said.
Piecing together the story
Already, the instruments on New Horizons are producing images that are setting astronomers minds abuzz with questions and possibilities.
So far, the spacecraft’s cameras have revealed several fuzzy features on Pluto -- a white doughnut-shaped area, an elongated dark smudge measuring some 1,800 miles in length that astronomers are calling “the whale,” a bright region that forms a heart and a string of black spots, each about the size of Missouri, that have gotten the nickname the “brass knuckles.”
From the images, it appears that darker regions are clustered around Pluto’s equator. It’s possible those spots could be evidence of material from Pluto’s inner regions that has been exposed as a result of impacts from incoming meteorites or other celestial objects.
"We're seeing probably ice caps, geologic features like valleys and mountains," van Belle said.
"We're kind of picking things out that would be like finding the continents on Earth right now."
It’s also becoming apparent that Pluto and its largest moon Charon are very different colors — Charon is a grayish color with a black blob on its pole while Pluto is more of a beige, reddish, ruddy color, Hall said.
Before, it was only known that Pluto reflected a lot of light and Charon didn’t reflect quite as much light, van Belle said.
The dark spot on Charon is puzzling astronomers because usually polar regions are bright with ice. But because that pole is facing toward the sun, that could actually be a warmer place on the Pluto moon, possibly accounting for its darker color, van Belle said.
More questions than answers
More than anything, the New Horizons images are opening up an even wider field of questions, Hall said.
“As (Lowell astronomer) Henry Roe puts it, as you start to get more and more information you realize not only did you have your hypothesis wrong, you weren’t even asking the right questions,” he said.
The coloring of Pluto and Charon for example, spurs questions about whether there have been different depositions of materials, varying impacts or distinct remnants of formation on each, Hall said.
"There have been some ideas that these two objects have a common origin so why do they look completely different?" he said.
It will also be interesting to compare the surface terrains of the dwarf planet and its moon and to see whether, because the two are locked in orbit with the same sides always facing each other, the surfaces facing outward are marked with craters while the other face is smoother. That’s the case with Earth’s moon, because its orbit also is locked in sync with our blue planet.
The influence of Pluto’s thin, tenuous atmosphere on its surface is another question on van Belle’s mind. The atmosphere has likely shaped Pluto's features somehow, a process that makes it very planet-like, said van Belle, who participated in the International Astronomical Union vote on Pluto's planetary status.
So far, there hasn’t been evidence of volcanoes on the icy planet, but that’s another distinct possibility, van Belle said.
Perhaps most exciting about the new Pluto information is the narrative astronomers will be able to piece together from this data, he said.
"There is a tremendous amount of storytelling you can get out of this and by that I mean you can talk about the story of how did Pluto form and make sure that jigsaw puzzle fits in with the other pieces we have, such as the existence of Charon and the nature of Charon because that story has to be consistent," van Belle said.
Looking at the images now, Hall emphasized that astronomers are just at the tip of the iceberg.
"At this point, it's just wild guessing," Hall said. “We’re just enjoying the ride.”