Pluto’s heart feature controls its winds
Pluto’s iconic heart feature, named Tombaugh Regio, functions as a “beating heart” that controls the small planet’s winds and might even play a role in shaping its surface features.
Planetary scientist and astrophysicist Tanguy Bertrand of NASA’s Ames Research Center in California, lead author of a new study published in the American Geophysical Union‘s (AGU) Journal of Geophysical Research: Planets, led a team of scientists who combined data collected by NASA’s New Horizons spacecraft during its July 2015 Pluto flyby with computer simulations of Pluto’s winds, weather, and nitrogen cycle.
Surprisingly, their computer simulation revealed that Plutonian winds 2.5 miles (four km) or more above the surface blow in a westward direction, which is opposite the planet’s eastward rotation, a phenomenon known as “retrorotation.”
Tombaugh Regio’s 600-mile (1,000-km) left lobe, known as Sputnik Planitia, a deep basin composed largely of nitrogen ice, is the most active region of the heart. It experiences a hydrologic cycle in which nitrogen ice evaporates into the atmosphere during the day, then condenses back into ice at night. This process creates nitrogen winds, which transport haze particles, heat, and ice grains. It also results in the creation of dark wind streaks in Pluto’s north and northwest regions.
Pluto’s atmosphere is composed largely of nitrogen, as Earth’s is, although the former’s atmosphere is 100,000 times thinner. It also contains small amounts of carbon monoxide and methane.
Bertrand compares the process of atmospheric nitrogen vaporizing, then condensing, to the beating of an actual heart. This repeated process literally pumps winds across the dwarf planet.
“This highlights that Pluto’s atmosphere and winds–even if the density of the atmosphere is very low–can impact the surface,” Bertrand said. Understanding the behavior of Pluto’s atmosphere will help scientists better understand Earth’s atmosphere, he emphasized.
Once Pluto’s winds reach Sputnik Planitia’s western high cliffs, they become trapped in the region for a while, then eventually escape.
“It’s very much the kind of thing that’s due to the topography or specifics of the setting,” stated Candice Hansen-Koharcheck of the Planetary Science Institute (PSI) in Tucson, Arizona.
If Pluto’s winds traveled in a different direction, the dwarf planet might have very different surface features, Hansen-Koharcheck noted.
Tombaugh Regio’s right lobe is composed primarily of nitrogen-rich glaciers and highlands.
Like many scientists, Bertrand was stunned when New Horizons revealed Pluto to be a complex world with varied terrains, as opposed to the featureless, dead rock many expected.
“This whole concept of Pluto’s beating heart is a wonderful way of thinking about it,” he stated regarding Sputnik Planitia’s role in Pluto’s wind patterns. “Sputnik Planitia may be as important for Pluto’s climate as the ocean is for Earth’s climate. If you remove Sputnik Planitia–if you remove the heart of Pluto–you won’t have the same circulation.”
Bertrand’s study was released just in time for the 90th anniversary of Pluto’s discovery by astronomer Clyde Tombaugh on February 18, 1930. Tombaugh Regio is named for him. A small amount of Tombaugh’s ashes were placed on the New Horizons spacecraft and are now traveling on a trajectory out of the solar system.
The Lowell Observatory in Flagstaff, Arizona, where Tombaugh discovered Pluto, is celebrating the milestone with an “I Heart Pluto Festival” that includes a talk by New Horizons principal investigator Alan Stern of the Southwest Research Institute (SwRI) in Boulder, Colorado, and a showcase of the astrograph and blink comparator Tombaugh used to make his discovery.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.