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NASA NEEMO 13 - Mission Day 9 Journal "Decompression Day"

Status Report From: NEEMO
Posted: Sunday, August 26, 2007

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The last full day of a saturation dive - one in which you've absorbed too much nitrogen to return quickly to the surface - is a busy one, and ours was no exception. We started with some robotics work, using a small manipulator to handle coral samples much the same way we might handle rock samples on the moon.

Then we went to work preparing for splashup tomorrow. First we packed all our tools and possessions in giant steel pots for transfer to the surface. We were only allowed to keep what we absolutely needed for the last half day. At 16:00, we closed the habitat's huge steel door, which has been open all mission. We started the 14-hour decompression with an hour of breathing pure oxygen from masks and then started slowly depressurizing the habitat (we simply opened a valve and connected ourselves to the atmosphere above the sea through a small tube). As I write this, Aquarius' air pressure is equivalent to being 17 feet deep in sea water, and our bodies are slowly 'blowing off' excess nitrogen we built up living at a depth of 45 feet for nine days. Aquarius itself is still sitting in about 47 feet of sea water, so the pressure outside is currently one atmosphere greater than the pressure inside. That exerts over 20,000 pounds of force on our thick steel door!

By 6 a.m. tomorrow, we'll be at surface pressure and will have lost enough of our excess nitrogen to safely swim to the surface without getting decompression sickness, or "the bends." Of course, we'll still be inside the habitat at the bottom of the ocean ... So, we'll quickly repressurize the habitat, open the door and swim to the surface using small scuba tanks, appropriately named "bail-out bottles." Our repress and bailout will be the equivalent of a 15-minute scuba dive - one that ends with us aboard a boat and in the sunlight for the first time in 10 days! After that, we're only a 40-minute ride from Key Largo and two days of post-dive observation.

We've had an amazing and educational mission, and we look forward to sharing it with all of you when we're back on the surface.

- The crew of Aquarius

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