Incredible image of Tombaugh Regio taken by the New Horizons spacecraft. Image: NASA/Marshall Flight Space Center
The vast heart-shaped plain on Pluto, which captured the imagination of people on Earth following our first close-up glimpse of the dwarf planet, might be hiding an ocean of slushy water ice.
While NASA’s New Horizons mission carries on into the outer edges of our solar system, its fly-by of Pluto back in May of this year continues to return incredible scientific data from the most famous of dwarf planets.
Astronomers and the public witnessed the first striking images that were returned to Earth, showing the enormous heart-like surface that has now been named Tombaugh Regio.
According to new research from the New Horizons team and other researchers, this plain may hold an exciting discovery. New data obtained from the mission suggests that beneath this enormous plain, there may lie a huge ocean of slushy water ice.
If true, it would help solve a decades-long puzzle: why does Tombaugh Regio align almost exactly opposite from the dwarf planet’s moon, Charon?
If a thick, heavy ocean does lie beneath the heart-shaped surface, the resulting ‘gravitational anomaly’ would be enough to pull Pluto’s moon into alignment over millions of years.
Another hint as to what lies beneath the region is the brightness of Sputnik Planitia – a giant impact basin in the region – in comparison to the rest of the dwarf planet.
A cutaway image of Pluto shows a section through the area of Sputnik Planitia, with dark blue representing a subsurface ocean and light blue for the frozen crust. Image: Pam Engebretson
The only answer that makes sense
Based on the data obtained during the NASA fly-by, this brightness could be explained by liquid nitrogen constantly refreshing, or convecting, as a result of a weak spot at the bottom of the basin.
As the heat rises through Pluto’s interior, the resulting effect would see the ice constantly churning.
The discovery of this weak spot in Sputnik Planitia’s basin also suggests that the planet’s crust in this region could be quite thin, suggesting that a massive impactor could have been enough of a trigger to cause a gravitational anomaly.
“We calculated Pluto’s size with its interior heat flow, and found that underneath Sputnik Planitia, at those temperatures and pressures, you could have a zone of water ice that could be at least viscous,” said New Horizons’ co-investigator Richard Binzel.
“It’s not a liquid, flowing ocean, but maybe slushy. And we found this explanation was the only way to put the puzzle together that seems to make any sense.”
The team’s research has now been published in Nature.
