Published: Feb 28, 2011 5:38 PM EST
Updated: Feb 28, 2011 2:38 PM EST

CAPE CANAVERAL, Fla.- Two astronauts are taking a spacewalk at the International Space Station.

Stephen Bowen and Alvin Drew floated outside Monday morning. Bowen, a spacewalking veteran, is a last-minute addition to the visiting crew of shuttle Discovery. He's filling in for an astronaut who hurt himself in a bicycle crash last month.

Drew, meanwhile, is now the world's 200th spacewalker. He's making his first spacewalk.

The two astronauts will install an extension cable and move a broken ammonia pump to a better storage location. And in a lighthearted experiment, they'll open a small metal canister and expose the interior to the vacuum of space. The bottle will be displayed in Japan.

This is the last flight for Discovery.

(Copyright 2011 by The Associated Press. All Rights Reserved.)