Life Beyond Earth, Part 2: Kevin Hand | Nat Geo Live

Summary

Planetary scientist Kevin Hand discusses the search for life beyond Earth, focusing on icy “ocean worlds.” Their surfaces may look inhospitable, but they could conceal vast reservoirs of liquid water. Possible examples include Europa, Ganymede, Callisto, Titan, Enceladus, and Triton.

A broader idea of habitability

Earlier thinking emphasized a “Goldilocks zone”: the right distance from a star for a planet to maintain liquid water on its surface. Ocean worlds suggest that a star’s warmth is not the only way to keep water liquid.

Tidal heating

As moons orbit giant planets, gravitational forces flex and stretch them, producing heat. Hand compares Io’s intense tidal activity to being “too hot” in this model: Io is highly volcanic and has lost any water it may once have had.

Callisto, by contrast, may have an ocean beneath a very thick, ancient ice shell. Europa may have a more suitable balance of tidal heating, potentially allowing its ocean to remain in contact with a rocky seafloor.

Why search these oceans?

Life on Earth depends on liquid water, and it exists even in extreme environments. Yet all known terrestrial life shares a common biochemical framework involving DNA, RNA, proteins, and ATP. Hand asks whether life elsewhere might have a different biochemistry or have originated independently.

Possible exploration approach

Hand describes a long-term vision for investigating Europa:

1. Send a lander capable of navigating the icy surface.
2. Deploy a heated probe to melt through the ice shell.
3. Release an autonomous underwater vehicle to explore the ocean.

Earlier steps could include sending spacecraft to fly by Europa, image its surface, analyze its chemistry, and use radar to investigate the ice–ocean boundary.

The lander, melt probe, and submersible are presented as a dream for future exploration. The talk also shows early robotic technology being used to explore extreme environments on Earth.

The significance of exploration

Hand recalls Galileo’s observations of Jupiter’s moons, which helped show that not everything orbits Earth. He compares that shift with later discoveries that physics, chemistry, and geology apply beyond Earth.

Biology, he argues, is the next major question. Whether life exists elsewhere remains untested, though current tools may make such tests possible.

Researchers and sources featured

• Dr. Kevin Hand — Planetary scientist and speaker; discusses his work with the Jet Propulsion Laboratory and NASA.
• Galileo Galilei — Historical astronomer whose observations of Jupiter and its moons are discussed.
• Mark Thiessen and others at National Geographic — Credited with producing the film segment showing technology for exploring extreme environments.
• Aliens of the Deep — The IMAX film excerpt used to illustrate Hand’s imagined Europa exploration scenario.