Shrugging off its ignominious downgrading from planet to dwarf planet status a few years back, Pluto burst back into the public spotlight when a space probe passed closer to it than any spacecraft ever had before, returning some stunning images of Pluto and its moons.
Taken as the craft sped by at 30,000 miles an hour, the images from the NASA New Horizons space probe show rugged mountains possibly as high as the Colorado Rockies and big ice features, that likely consist of nitrogen or methane ice, rather than water.
Pluto is so far away that it takes 4.5 hours just to send the signal – which travels at the speed of light at 186,000 miles per second – from New Horizons to the Earth.
“One of the fascinating things to me is that it went 3 billion miles and arrived 72 seconds early seventy two seconds early,” says John O'Meara, a St. Michael's College physics professor. “To know that you've been flying for 9.5 years and you managed to get it right by within 72 seconds is amazing.”
The probe will be sending back images and data gathered from a variety of instruments over the next 16 months.
“The data transfer rate from New Horizons is slow and it's so far away, that it's actually going to be not until the end of 2016 that we start getting all the data from just this quick flyby,” he says.
O’Meara says of the many instruments on board the space probe there’s a spectrograph, which breaks light into its constituent colors and can give clues about the chemistry on Pluto, including the ratios of different elements present such as methane and carbon dioxide.
And he says a suite of imaging equipment that analyzes materials in color and infrared is named after characters in the Honeymooners.
“And so we're going to we're going to learn all about Pluto and it's tenuous thin atmosphere and it's larger moon Charon and the other small moons orbiting around it,” O’Meara says.
Not only is the probe sending data back, but it carries with it 30 grams of the ashes of Clyde Tombaugh, the astronomer who discovered Pluto.
Water on Pluto?
O’Meara says it’s highly unlikely that there is water on the surface of the dwarf planet.
“If there is water it would be subsurface, and it would be very much probably just solid, ice,” he says, noting there is methane ice all over Pluto.
O’Meara says one of the more interesting things the first set of images has shown is that there's very flat regions out on Pluto’s surface that appear to have almost no craters:
“We expect things which had formed billions of years ago to be pocketed with craters, and so that means something is going on the surface to replenish the surface to fill it in much in the same way on Earth,” he says.
We don't see craters all over the surface of the earth because we have erosion, wind and water filling in the gaps. But on places like the moon without these elements, the surface is covered in craters.
“Pluto is surprising us in balance because it has these regions without craters, and so something is happening geologically on Pluto that I think we're going to spending a long time trying to figure out.”
Where to next, New Horizon?
The New Horizon space probe has already hurtled past Pluto on its fly-by mission. Now, as it keeps traveling away from Earth it is hopefully going to pass either one or two Kuiper Belt objects on its way out.
The probe doesn’t carry much fuel because it’s so heavy, but it has small amounts to fuel thrusters that can allow very minor course corrections to its trajectory.
Any images and data it could garner would help to “to really understand the outer parts of the solar system and how all the pieces of how the solar system formed about 4.5 billion years ago,” says O’Meara.
Kuyper belt objects are typically about the size of 20 to 30 miles in diameter.
If it reaches the Kuiper Belt, it would be the first spacecraft to get close to the ring of icy blocks of debris that encircle our solar system.