What on Earth was that grinding, thudding, scraping sound? No, it wasn’t astronauts clumping around on the Space Station, a washing machine in the midst of a cycle, or space dust hammering the Space Shuttle. It was actually the Coast Guard’s newest and most technologically advanced ice breaker — the Healy — barreling through thin, first-year ice in the Chukchi Sea north of Alaska. (Multiyear ice tends to be less briny and have more air bubbles than first-year ice.) NASA science writer Kathryn Hansen is on board as part of the ICESCAPE mission, and she had this to say about the sound:

On July 7, I took a trip down into the bowels of the Healy’s bow to record the sound of the ship’s hull pummeling through thin, first-year ice (mp3 above). The rhythm and crescendos reminded me of the percussion section of an amateur orchestra.

Interestingly, icebreaking sounds completely different depending on your location in the ship. From outside on the ship’s deck you can hear the ice cracking and ocean water rushing in to fill the void. From inside in the science lounge, add the effect of vibrating bookshelves and the demise of items not properly secured.

These sounds (not to mention the earthquake-like movement) eventually blend into the background and sleep comes easily. The strange part will be returning home at the end of the month to a “quiet and still” life in the city.

By now you might be wondering, how much ice can the Healy break? Cruising at 3 knots, the ship is rated to break 4.5 feet of ice. By backing and ramming, the ship can break through 8 feet. Breaking thicker ice is possible but would take more time.