Dr. Robert Satcher Jr. and Randolph Bresnik - the father of a new baby girl - got started on the work an hour late.
A valve on the drink bag in Satcher's suit came off as he was getting ready for the spacewalk. To everyone's relief, the valve to the water pouch went back on tightly. The concern was that big blobs of water could float up and get in his eyes if the valve came loose during the spacewalk.
They did their best to make up lost time, quickly getting ahead in their main chore, the installing a fresh oxygen tank. The 1,200-pound tank of high-pressure oxygen, delivered last week by Atlantis, needed to be attached to NASA's station air lock, a chamber leading out to the vacuum of space.
The spacewalkers also had some science experiments to hang on the orbiting outpost.
The first two spacewalks of Atlantis' weeklong space station visit went so well, and the astronauts accomplished so much extra work, that only a few chores remained.
Lightning storms caught Bresnik's eye as he toiled 220 miles up. "Where we over?" he called out. The answer: Micronesia.
Bresnik was still celebrating the birth of Abigail Mae. She arrived just hours after his first-ever spacewalk Saturday.
His wife, Rebecca, delivered the six-pound, 13-ounce girl back in Houston. Both baby and mother were said to be doing well.
Atlantis and its crew of seven will depart the space station Wednesday. The shuttle will aim for a landing back at Kennedy Space Center on Friday.