The Deep Submergence Science Committee posted this photo of the Alvin being tested in port before dive certification. https://www.facebook.com/pages/DeSSC-Deep-Submergence-Science-Committee/288538814501728

Oceanographers the world over have done without everyone’s favorite submarine since 2011, when the submersible Alvin went in for a major makeover. But after a two-year-long spa day, the sub that discovered hydrothermal vents and first surveyed the wreck of the Titanic is back in the water and expected to be certified to dive in a few days.

Map source: https://www.fas.org/irp/imint/docs/rst/Sect11/Sect11_7.html

The new sub has received a number of improvements, the most notable being its larger, thicker titanium core. This spherical core is now rated to withstand depths of 6500 meters (4 miles), compared to the old core which was rated at 4500 meters (2.8 miles). There are huge swaths of the ocean below 4500m water depths (see the map to the right) that are now open to exploration by the Alvin. Given that only about 10% of the ocean has been explored, this is a boon for explorers and explorers-at-heart everywhere. (To download a Google Maps visualization of where the Alvin has explored so far, click here.) Other improvements include new HD cameras for upgraded video footage, additional portholes for improved visibility, and an increased capacity to bring scientific samples back up to the surface.  BBC News posted a great video last February highlighting the major changes.

The design of the Alvin is elegantly simple. The central titanium sphere holds two scientists and a pilot, and is couched in a body of syntactic foam made of microscopic hollow glass spheres which makes the submarine buoyant. The sub uses ballast to sink to the bottom, and when it’s time to resurface simply drops the ballast and floats back to the surface.

The sleek design of the Alvin has enabled oceanographers to study the ocean in a way no other instrument can. Since its inception in 1964, the Alvin has helped to solidify major aspects of the theory of plate tectonics, identified over 300 deep-sea species, and discovered the vibrant and strange ecosystem  of hydrothermal vents, which were completely unknown before 1977. With its improved capabilities, we’ll be looking forward to what new horizons the Alvin will reveal in coming years.