The Bathyscaphe Trieste was a deep-sea research craft that became the first crewed vehicle to reach the deepest known point in the ocean. On January 23, 1960, Jacques Piccard and Don Walsh descended to the Challenger Deep in the Mariana Trench. Their dive showed that humans could explore extreme ocean depths using careful engineering, buoyancy control, and pressure-resistant design.
The mission remains a landmark in marine science and ocean exploration.
Trieste worked differently from most submarines because it used a large gasoline-filled float for buoyancy and a small steel pressure sphere for the crew. Gasoline is less dense than seawater and does not compress much, so it helped support the craft at great depth. Heavy iron shot ballast made the vehicle sink, and releasing the ballast made it rise.
This balance of weight, buoyant force, and pressure protection allowed Trieste to descend nearly 11,000 meters into the dark trench.
Key Facts
- Trieste reached the Challenger Deep on January 23, 1960.
- Approximate maximum depth of the dive was 10,916 m below sea level.
- Pressure increases with depth according to P = P0 + ρgh.
- Buoyant force is given by Fb = ρfluid g Vdisplaced.
- Trieste descended by carrying dense iron shot ballast and ascended by releasing it.
- The crew rode inside a pressure sphere designed to resist extreme water pressure.
Vocabulary
- Bathyscaphe
- A deep-diving crewed vehicle that uses a buoyant float and a pressure sphere to explore great ocean depths.
- Buoyancy
- The upward force a fluid exerts on an object that displaces the fluid.
- Ballast
- Heavy material added to a vessel to help it sink or stay stable in water.
- Pressure sphere
- A strong spherical compartment that protects crew members from extreme water pressure.
- Challenger Deep
- The deepest known part of Earth’s oceans, located in the Mariana Trench.
Common Mistakes to Avoid
- Thinking Trieste used propellers to power itself straight down is wrong because its vertical motion mainly came from changing its overall density with ballast and buoyancy.
- Treating water pressure as the same at all depths is wrong because pressure increases nearly linearly with depth according to P = P0 + ρgh.
- Assuming the entire vehicle had to be pressurized for the crew is wrong because only the small pressure sphere needed to hold a safe internal pressure.
- Forgetting the role of the gasoline float is wrong because the float provided the large volume needed for buoyant force while resisting compression better than air.
Practice Questions
- 1 Use P = P0 + ρgh to estimate the pressure at 10,916 m depth. Let P0 = 1.01 x 10^5 Pa, ρ = 1025 kg/m^3, and g = 9.8 m/s^2.
- 2 A bathyscaphe displaces 150 m^3 of seawater. Using ρ = 1025 kg/m^3 and g = 9.8 m/s^2, calculate the buoyant force on it.
- 3 Explain why releasing iron shot ballast causes the Trieste to rise even though the gasoline float stays the same size.