Evidence is mounting that Pluto has a hidden ocean that could potentially be a habitat for life. Scientists believe it is buried beneath the dwarf planet's frozen surface and contains as much water as all Earth's seas.
Image: picture-alliance/Bildagentur-online/Saurer
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Observations by NASA's New Horizons spacecraft - managed from Johns Hopkins University - indicate Pluto may have rolled over on its axis eons ago, the result of tidal forces with jumbo moon Charon, NASA scientists said on Wednesday.
"It's a big elliptical hole in the ground, so the extra weight must be hiding somewhere beneath the surface. And an ocean is a natural way to get that," lead author Francis Nimmo of the University of California, Santa Cruz, said in a statement.
NASA spacecraft approaches new horizons with dwarf planet Pluto flyby
For nine years, NASA's New Horizons spacecraft has been travelling through our solar system. On its way, it's visited an asteroid and the planet Jupiter. Now, it's reaching its goal: Pluto.
Image: JHUAPL/SwRI
First glimpse of Pluto
This is one of the most recent images of Pluto - taken by NASA's New Horizons spacecraft. By Tuesday the pictures will become sharper and better as the unmanned probe gets closer and closer to the dwarf planet.
Image: picture-alliance/dpa/NASA/JHUAPL
Just a stone's throw away
The big day is July 14 - and long awaited by NASA researchers. New Horizons will pass Pluto from a distance of 12,000 kilometers, which seems far away. But let's compare: the distance from our moon to Earth is thirty times as far, so 12,000 kilometers is pretty close! And this is how things will look, with Pluto's largest moon Charon in the background.
Image: JHUAPL/SwRI
The planet that wasn't to be
Seven months after New Horizons launched, the International Astronomical Union (IAU) cancelled Pluto's planetary status. It is now referred to as a "dwarf planet" as its solar orbit is not sufficiently circular - it is more elliptic. It was the first time the IAU had defined what constitutes a "planet," and came because too many objects had been discovered in the solar system.
Image: picture-alliance/Bildagentur-online/Saurer
Comparison by size
The planets closest to the Sun are Mercury, Venus, Earth and Mars. Then there's the dwarf planet Ceres, followed by the giants Jupiter, Saturn, Uranus und Neptune. On the outer fringes of the solar system there are two tiny dots: Pluto and its moon Charon. New Horizons data shows Pluto's diameter to be a little larger than previously thought, at around 2,370 kilometers (1,473 miles).
Image: picture-alliance/dpa
Not all of Pluto's moons are round
It is hoped New Horizons will investigate Pluto's moons, and discover, for instance, the true size of Styx. It is one of Pluto's moons, and is thought to have a diameter of somewhere between eight and 28 kilometers. The probe took its first pictures of Charon, Nix and Hydra in January and February. In April, it got shots of Kerberos. But NASA expects higher resolution images very soon.
Image: NASA/ESA/A. Feild (STScI)
Wild dance in the lunar orbit
The moon Nix spins around wildly in its lunar orbit. These are not pictures taken by New Horizons, but a computer simulation by NASA scientists, based on existing data. What makes things complicated is that Nix not only circles in an orbit around Pluto, but is also influenced by the gravity of Charon - so the one moon is also a moon of another moon.
New Horizons is equipped with three optical instruments, which can take pictures in a large variety of spectral bands. Two plasma spectrometers can analyze particles such as those emitted by the solar wind. The spacecraft also features dust sensors and radiometers.
Image: JHUAPL/SwRI
"Big" camera
Here, engineers are installing the Long Range Reconnaissance Imager (LORRI) on the New Horizons probe. LORRI is a digital camera that registers wavelengths of visible light: the heaviest part of the 8.6 kilogram camera is its 5.6 kilogram telescope.
Image: NASA
Best part of a decade
New Horizons was launched on January 19, 2006, from the Cape Canaveral Air Force Station in Florida, aboard an Atlas V rocket. The spacecraft immediately entered a trajectory designed to overcome the Earth's gravity and that of the sun. To do that it needed a speed of more than 16 kilometers per second - that's more than 58,000 kilometers per hour (37,000 mph), and with it a world record.
Image: NASA
Farther and farther from the sun
The trajectory of New Horizons has taken it straight for the far reaches of our solar system. On its way, New Horizons has visited the asteroid 132524 APL, as well as the planet Jupiter, which the probe passed at a distance of 2.3 million kilometers. It collected data about Jupiter's atmosphere, its magnetosphere, and its moons.
Image: NASA
Coming soon: "new and improved" images!
NASA was able to fix a few technical difficulties with New Horizons recently and the spacecraft is now again fully operational. Hopefully, nothing will now stop it from delivering fascinating new pictures of the dwarf planet Pluto.
Image: JHUAPL/SwRI
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The studies focus on a 600-mile long, 250-mile wide and 2-mile deep basin - known as Sputnik Planitia after the Russian satellite that launched the Space Age in 1957 - in the left lobe of Pluto's heart-shaped region.
Subsurface oceans may also be on other similarly sized worlds orbiting in the Kuiper Belt, a so-called twilight zone on the fringes of our solar system, according to Nimmo. "They may be equally interesting, not just frozen snowballs," he noted.
Despite being about 40 times farther from the sun than Earth, Pluto has enough radioactive heat left over from its formation 4.6 billion years ago to keep water liquid.
