Five Pluto mysteries that NASA's New Horizons spacecraft could solve

Once a planet and now a Kuiper Belt object, Pluto remains largely a mystery to astronomers. NASA's New Horizons space probe, now just a month away from its first observations of the mysterious dwarf planet, could provide some answers.

An artist's impression of NASA's New Horizons spacecraft, currently en route to Pluto, is shown in this handout image provided by Science@NASA. After nine years and a journey of 3 billion miles (4.8 billion km), NASA's New Horizons robotic probe has been woken from hibernation to begin its unprecedented mission: the study of the icy dwarf planet Pluto and its home, the Kuiper Belt.

Having traveled nearly three billion miles, the space probe on its way to explore the edges of our solar system, has awoken from hibernation for the final time and is now about 7 months away from its closest approach to Pluto.

The American astronomer Clyde Tombaugh discovered Pluto more than seven decades ago, but his discovery has not yet been visited by a spacecraft. Pluto is distant and small – so small that in 2006 the International Astronomical Union reclassified it as a "dwarf planet" – so that even a halfway decent view requires massive telescopes like the Hubble.

NASA scientists have been waiting nearly nine years since New Horizons's launch, but they'll have to wait at least another month, when the spacecraft will start observing Pluto, to try to answer some of the questions about the dwarf planet that have puzzled scientists since its discovery.

1) How many moons does Pluto actually have? And why does it matter?

Before New Horizons launched, scientists knew of three moons orbiting Pluto. Now the number stands at five, but there could be more. Getting better visuals of Pluto's satellites can help scientists more accurately calculate both the mass and density of the dwarf planet. As for the whole system, knowing how many moons are present can shed light on its origins.

2) What is Pluto's surface made of?

Scientists know that Pluto's surface includes nitrogen, carbon monoxide, methane, and water ices. This could mean that Pluto has a thick layer of nitrogen ice at its surface. The hardness of its surface can determine whether Pluto can stand up to hits by other objects in the Kuiper Belt – a disk of icy dwarf orbiting past Neptune –  or if craters would form upon impact. And for scientists to fully understand what level of bombardment bodies in our outer solar system, like Pluto, faced during their history, they need to know if impacts with other bodies would leave any mark.

"There could even be liquid nitrogen on the surface, which could smooth out any impact craters," Alan Stern, one of the mission's principal investigators from Southwest Research Institute, told TIME.

3) What's up with Pluto being a double planet?

Yes - Pluto actually has a companion. Discovered in 1978, Charon is one of Pluto's moons but is so large that the pair is considered a binary system. Some scientists believe that at some point Pluto and another one of the icy bodies swirling through Kuiper crashed into one another and that the leftover debris from the collision coalesced over time, forming Charon. The New Horizons mission may allow astronomers to determine just how Pluto's system, with its second planet and several moons, could form.

4) Does Pluto have seasons?

Because of Pluto's peculiar orbit and the fact that its north pole seems to be tipped on its side, surface temperatures vary considerably. Most scientists believe that when Pluto is at its closest distance from the Sun, temperatures rise and form a gaseous atmosphere, but as it gets farther away, that atmosphere may freeze and precipitate to the dwarf's surface. This phenomenon of intense seasonal changes may be unlike any planet in our solar system, but astronomers don't know just yet what happens as Pluto orbits the Sun.

5) Is the Pluto system just the first glimpse of a whole lot more?

Astronomers have already partly figured out this question, and the general answer is yes. But scientists know almost nothing about the extent of the Kuiper belt – even whether the icy bodies that make up the belt should be counted in billions or trillions.

"For decades we thought Pluto was this odd little body on the planetary outskirts," said Hal Weaver, New Horizons Project Scientist at the Johns Hopkins University Applied Physics Laboratory, in a statement. "Now we know it's really a gateway to an entire region of new worlds in Kuiper Belt, and New Horizons is going to provide the first close-up look at them."

[Editor's note: An earlier version misstated the distance New Horizons was from its closest approach to Pluto.]

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to

QR Code to Five Pluto mysteries that NASA's New Horizons spacecraft could solve
Read this article in
QR Code to Subscription page
Start your subscription today