Pluto May Have Nitrogen Lakes That Freeze and Thaw
Data collected by NASA’s New Horizons spacecraft shows that tiny, distant Pluto not only likely has an ocean beneath its frozen face, but also may have had lakes on its surface in the recent past and likely will have them again in the future.
Data collected by NASA's New Horizons spacecraft shows that tiny, distant Pluto not only likely has an ocean beneath its frozen face, but also may have had lakes on its surface in the recent past and likely will have them again in the future.
Even on its warmest days, Pluto is far too cold for surface lakes made of water, but they could contain liquid nitrogen during periods of time when the planet's atmosphere bulks up.
Pluto, which takes 248 years to circle the sun, turns out to have large swaths of real estate with direct overhead sunlight due to an extreme axial tilt of 120 degrees, relative to its orbital plane. Earth, by comparison, is tilted 23 degrees.
That gives Pluto a much broader range of tropical latitudes than Earth, noted New Horizons scientist Richard Binzel, with Massachusetts Institute of Technology.
Because arctic and tropical zones alternatively extend over such wide swaths of the dwarf planet's surface, Pluto has regions where both extremes occur, though not at the same time.
Pluto also has a wobble, which causes its axis to tilt up an additional 20 degrees from its present orientation, triggering long-term climate cycles that far exceed anything experienced on Earth, Binzel said.
Pluto is now in an intermediate phase between its climate extremes, with the last peak occurring less than 1 million years ago. Temperatures today measure about minus-400 degrees Fahrenheit.
Variations in the amount of sunlight falling on Pluto have direct impacts on Pluto's atmosphere, noted New Horizon's lead scientist Alan Stern, with the Southwest Research Institute.
"We find that Pluto's atmospheric pressure today is atypically low and that in the past it could have been 1,000 to 10,000 times higher," exceeding the pressure of Mars by up to 40 times, Stern said.
Computer models show that when Pluto's temperature and atmospheric pressure are high, conditions could be suitable for liquid nitrogen.
Additional evidence comes from New Horizons itself. High-resolution images taken during the July 14 flyby reveal features that look like they could have been carved by liquids. The pictures also show what appears to be a frozen lake, measuring about 20 miles across at its widest point, that is located just north of Sputnik Planum, the western lobe of Pluto's smooth, heart-shaped region.
"Pluto is so dynamic that different cases may apply in different epics," Stern said. "We found this little planet where everything is coupled together."
The research was unveiled at the Lunar and Planetary Science Conference last week in Texas and has been submitted for publication in the journal Icarus.
This feature appears to be a frozen, former lake of liquid nitrogen, located in a mountain range just north of Pluto’s informally named Sputnik Planum. Captured by the New Horizons’ Long Range Reconnaissance Imager (LORRI) as the spacecraft flew past Pluto on July 14, 2015, the image shows details as small as about 430 feet (130 meters). At its widest point the possible lake appears to be about 20 miles (30 kilometers) across.
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.