How does volatile ice affect Pluto’s axis?

Vocabulary: Pluto, tidal axis, subsurface ocean, crust, fault lines

NGSS: MS-ESS1: Earth’s Place in the Universe, SEP2: Developing and Using Models, SEP4: Analyzing and Interpreting Data, CC4: Systems and System Models, and CC2: Cause and Effect: Mechanism and Explanation.

Common Core State Standards: CCSS.ELA-LITERACY.RI.6.1, CCSS.ELA-LITERACY.RI.7.1, CCSS.ELA-LITERACY.RI.8.1, CCSS.ELA-LITERACY.RI.9–10.1, CCSS.ELA-LITERACY.RI.11–12.1

Charon in Enhanced Color NASA’s New Horizons captured this high-resolution enhanced color view of Charon just before closest approach on July 14, 2015. Credits: NASA/JHUAPL/SwRI

One of the most recognizable features on Pluto’s surface is a massive, heart-shaped basin. Now researchers say that as ice accumulated in part of that basin, it appears to have tipped the dwarf planet on its axis. Sophie Bushwick of Popular Science discusses the finding.

Audio Excerpt “Pluto Rolls Over (the Dwarf Planet, Not the Dog)” 11/18/2016. (Original Segment)

Print this segment transcript.

Questions

• Explain what caused Pluto to “roll over”.
• Pluto’s surface temperature is estimated to be -240 degrees Celsius (-400 degrees Fahrenheit), but it has a liquid-y ocean. Do you think that Pluto’s subterranean ocean has the same composition as our oceans? Why or why not?
• How did fault lines help scientists uncover movement of Sputnik Planitia? What other evidence do you think scientists still need in order to verify this finding?
• Based on the movement of Sputnik Planitia, would you say that Charon (Pluto’s closest moon) is similar to Pluto’s size or much smaller than Pluto?

This animation shows how Pluto reoriented in response to volatile ices filling Sputnik Planitia (the left lobe of Pluto’s “Heart”). Sputnik Planitia started northwest of its present position, and as it filled with ices, the tides from Charon (Pluto’s largest moon) caused the entire dwarf planet to reorient, and align Sputnik Planitia with Pluto’s tidal axis (the line running through Pluto and Charon). If Sputnik Planitia is still accumulating ice, then Pluto may still be reorienting. Credit: James Tuttle Keane. Maps of Pluto and Charon by NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Activity Suggestions

• Have students create models using clay that simulate the movement of “Sputnik Planitia” in response to Charon’s gravitational pull. Look at this video on the interesting and weird moons of Pluto.
• Check out these resources on the New Horizons mission and take your students on a flyover using this video created from the surface data it collected from Pluto.

[Learn more about Pluto with one of our most up-close and personal shots of the (dwarf) planet and an interview with the deputy lead of the New Horizon mission.]