Pluto Probably Has an Ocean Under its Surface
NASA's New Horizons probe has revealed geological surprises and a hint of underground ocean on the dwarf planet.
Despite being so far from the sun, tiny Pluto, which is smaller than Earth's moon, has had an active geologic life from the start, one that continues to present day, research published on Thursday shows.
The evidence is all over Pluto's face, which was observed close-up for the first time by NASA's New Horizons spacecraft on July 14, 2015.
With most of the high-resolution images from the flyby now back on Earth, scientists say Pluto's mountains, glacial flows, rotated ice blocks, volcano-like mounds and other features rival the geology found on much larger, warmer planets like Mars.
The physical and chemical conditions on Pluto, located about 40 times farther away from the sun than Earth, have played out in unusual and largely unforeseen ways. Highly volatile cryogenic ices, such as nitrogen, carbon monoxide, methane, vaporize into Pluto's hazy and surprisingly compact atmosphere. Internal heating, fueled by the natural decay of radioactive elements in Pluto's rocks and other sources, likely keeps an ocean of ammonia-rich water liquid beneath the dwarf planet's frozen surface.
"We now have half a dozen worlds, like (Saturn's moon) Enceladus, (Jupiter's moons) Europa and Ganymede, and now Pluto, that seem to have oceans in their interiors," New Horizons' lead scientist Alan Stern, with the Southwest Research Institute told Discovery News.
"It's interesting that only Earth wears its ocean on the outside," he said. "From the surface, we don't see them. Who know that oceans would turn out to be fairly common?"
As far as the prospect for life on Pluto, Stern said, "Anytime you have liquid water, the astrobiologists get interested in that place. That's as far as I'm willing to go."
For Earth-like life to exist, a planet would need water, an energy source, the right chemical elements and time, added planetary scientist William McKinnon, with Washington University in St. Louis.
"All we can say is that we think that Pluto has an ocean and we think that this ocean has survived to the present day. It's the kind of ocean that is deep inside the interior of Pluto, in total darkness. But, it would lie between a floating water ice shell and the rocky interior, so it would be in contact with rock. There would be a modest amount of heat leaking out. You certainly couldn't rule it out, but anything about life on Pluto is simply speculation," McKinnon told Discovery News.
New Horizons scientists also discovered that Pluto's primary moon Charon was once active as well, but has been geologically dead for about 2 billion years, with its one-time liquid ocean now frozen solid.
A related study shows that Charon and Pluto's four small moons -- Nix, Hydra, Kerberos and Styx -- formed from debris blasted into space after a Pluto-sized body and Pluto smashed into each other some 4 billion years ago.
The research is published in five papers in this week's Science.
Although Pluto lives in the cold outermost reaches of the solar system, internal heating may maintain an ammonia-rich sub-surface ocean.
Newly returned pictures taken by NASA’s New Horizons spacecraft are giving scientists -- and the rest of us -- the most detailed views of Pluto’s stunningly diverse landscape. “We continue to be amazed by what we see,” NASA chief scientist John Grunsfeld said in a statement. The latest images form a strip 50 miles wide and were taken when New Horizons was about 15 minutes away from its closest approach to Pluto on July 14.
As NASA’s New Horizons spacecraft raced toward a July 14 close encounter with Pluto, the probe’s telescopic long-range camera got to work on a sequence of pictures that revealed features smaller than half of a city block. Pluto’s surface turned out to be unexpectedly diverse, evidence of a complicated and rich geology. The mosaic pictured here starts about 500 miles northwest of Pluto's smooth Sputnik Planum region and covers the rugged al-Idrisi mountains, the shoreline of Sputnik Planum and its icy plains.
This image has been scaled and rotated, for the full, high-resolution view,
Scientists aren’t sure yet how some of Pluto’s craters came to contain layers, such as the one picture here in the upper right. “Layers in geology usually mean an important change in composition or event, but at the moment New Horizons team members don’t know if they are seeing local, regional or global layering,” NASA said. New Horizons’ Long Range Reconnaissance Imager (LORRI) took a series of images about 15 minutes before the spacecraft’s July 14 close encounter with Pluto. The dark crater at the center of the image is apparently younger than the others because material thrown out by the impact is still visible. Most of the craters are within a 155-mile wide region known as Burney Basin, the outer rim of which appears as a line of hills at the bottom of this image.
New Horizons gathered a 50-mile-wide view of Pluto’s rugged northern hemisphere, including a 1.2-mile high cliff, seen here from the left to the upper right, during a series of pictures taken by the spacecraft’s telescopic Long Range Reconnaissance Imager (LORRI) on July 14. The cliff is part of a canyon system that stretches for hundreds of miles across Pluto’s northern hemisphere. Scientists believe the mountains in the middle are comprised of water ice that has been changed by the motion of nitrogen or other exotic ice glaciers over the eons. At the bottom of the image, which was taken when New Horizons was about 10,000 miles from Pluto, the badlands meet the giant icy plains of Sputnik Planum.
Blocks of ice, upper left, appeared to be jammed together in an area the New Horizon scientists are calling the al-Idrisi mountains. Some of the mountains seem to be coated with a dark material, while others are bright. Scientists think material crushed between the mountains may be from the ice blocks jostling back and forth. The mountains end at the shoreline of a region named Sputnik Planum, which is marked by soft, nitrogen-rich ices that form a nearly flat surface. New Horizon’s Long Range Reconnaissance Imager (LORRI) took a series of images in the span of about one minute at 11:36 Universal Time on July 14, about 15 minutes before the spacecraft’s closest approach.