How Jupiter’s Moon Is Pulled Like a Rubber
6 Minutes
Jupiter's moon Europa explained for students, exploring how tidal flexing creates a subsurface liquid ocean. A Tamil science lesson.
- Signs of an ocean and water vapour plumes on Jupiter's moon Europa
- How tidal flexing from an elliptical orbit melts subsurface ice
- Why Jupiter's radiation creates a thin oxygen atmosphere
What this lesson teaches
Europa, one of the four largest moons of Jupiter, hides a vast liquid ocean beneath a thick crust of ice because Jupiter's gravity continuously stretches and squeezes the moon, generating heat through a process known as tidal flexing.
Discovery of the frozen moon
Four hundred years ago, the astronomer Galileo Galilei discovered Europa using a telescope, making it one of four large moons orbiting Jupiter alongside dozens of smaller ones. In 1979, observations from the Voyager spacecraft hinted that Europa had an ocean hidden under an outer ice shell between 15 and 25 kilometres thick. Scientists calculate that this underground ocean contains more than twice the amount of water found across all of Earth's oceans combined. Space probes visiting since 1973 have sent back clearer pictures and information about how this frozen moon behaves.
How tidal flexing creates heat
Europa takes about 3.5 days to complete an elliptical, or oval-shaped, orbit around Jupiter. As it travels, it periodically comes closer to the giant planet, where intense gravitational pull stretches it, and then moves farther away, allowing it to contract. In the same way that stretching and releasing a rubber band repeatedly generates heat, this non-stop flexing creates friction and warmth deep within the moon. This internal heat keeps the subsurface water from freezing into solid ice, even though Europa's outer surface remains between minus 160 and minus 220 degrees Celsius.
Evidence of water plumes
- In 2012, the Hubble Space Telescope captured images showing fountains of water vapour shooting up from Europa's icy surface.
- These towering vapour plumes erupt to heights of roughly 160 kilometres into space before falling back down.
- Scientific research conducted in 2019 confirmed that these active plumes are made of water vapour escaping directly from the subsurface ocean.
- This confirmed that liquid water has existed beneath the ice for millions of years, leading scientists to study whether living organisms could survive there.
Why Europa has thin oxygen
- Intense radiation traveling outward from Jupiter directly strikes the water ice covering Europa's surface.
- This radiation breaks apart water molecules into their chemical building blocks, separating hydrogen and oxygen.
- The escaping oxygen gathers into a thin atmospheric layer surrounding the moon.
- Humans cannot live there because Jupiter's powerful radiation is dangerous, and the entire atmosphere holds only enough oxygen to fill about twelve stadiums.