The MR1 sonar fish is extremely sensitive to sound. A loose washer around a bolt, tapping on the outside of the fish, can cause enough noise to interfere with the sonar signals. Tonight we reeled in the MR1 to tighten and glue some washers back in place. But how did already glued-down, tight washers get loose?

“The plastic on the outside of the sonar fish probably shrank a bit,” Jenny Engels explains. The 10-foot long plastic body around the MR1 can contract and expand about a one-forth of an inch when exposed to changes in temperature,” Steve Tottori says. After sitting in the sun during our transit from Costa Rica, the cold Humboldt Current around the Galápagos may have shrunk the plastic body of the MR1 enough to rattle a few washers.

Since MR1 listens for sounds in a specific frequency range (11-12 kHz), a loose washer can be pretty distracting - like trying to pick out the horn during a rock and roll concert. It's much easier when only the horn is playing.

In the last two days we’ve mapped about 7,200 square kilometers of seafloor - an area larger than the State of Delaware. So far, the sonar images have revealed landslides of various sizes, hundreds of volcanic cones, and large areas where we think lava oozed out onto the seafloor. The mapping fun has just begun.

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