With Kelly's demanding NASA job, the couple was lucky to spend 10 days a month together, scheduling in time between his training calendar and her travels between Washington and Arizona. But their emotional bond was strong, sharing their lives through hour-long phone conversations every night they were apart.
In the hospital, Kelly is closely monitoring his wife's recovery, tackling every detail with the same focus he brings to his job as a space shuttle commander. In the first days after the attack, he slept in the hospital and only recently has begun to stay in a hotel across the street.
Though the couple owns a condo just two miles away from the hospital, Kelly prefers to be as close as possible to his wife's bedside, where he tells her he loves her and reads out loud some of the thousands of supportive letters and emails that have flooded in since the attack.
So far, doctors say Giffords' recovery has been nothing short of miraculous. Last Saturday, she was removed from a ventilator, and on Monday her condition was upgraded to serious from critical condition. Doctors have inserted a tracheotomy tube in her throat to help her breathe and put a feeding tube in her stomach.
While his wife has yet to speak or hint at how much she understands, Kelly has witnessed Giffords following instructions, like a command to hold up two fingers.
"I can hold up a pen and I could say, 'Take the pen.' And she could take the pen," he said. "And then I could say, 'Give me back the pen,' and she'll give it back. It's really good progress."
Doctors have been unsure whether Giffords is actually able to see, but Kelly is confident that she's looking at him from her one unbandaged eye.
Kelly hopes his wife will make a complete recovery, and so far doctors have ruled nothing out. Always the commander, he's even set goals for her, telling her she'll be up and walking in two weeks. But Kelly knows his wife has a long road ahead, a recovery that will be measured in months and maybe longer.
When Giffords does begin to speak, Kelly knows they have plenty to talk about, like having to tell her about the six people who lost their lives in the attack, including 9-year-old Christina-Taylor Green and one of her dedicated staffers, Gabe Zimmerman.
Then there's the question of his future and whether Kelly will be the commander of the final space shuttle mission on April 19, known as STS-134. This past weekend, his crew sent a supportive tweet, saying "Gabby is improving. Mark is strong ... STS134 will succeed."
Kelly's mission is a significant honor, commanding the final flight of the space shuttle program. He hopes to be able to discuss the matter with his wife before he decides whether to return to space. NASA has sent a colleague to help him in Tucson, and a NASA psychologist has even been providing him counsel in the days since the attack.
"I'm hopeful that I will be able to rejoin my crew, finish getting ready for this mission and launch of April 19," he said. "I mean, my first priority is her. You know, she needs me to be by her side."
Giffords and Kelly will also have to decide whether she'll resume her work.
Sawyer asked, "Do you want her to go back into Congress after this?"
"That's a tough, tough decision. Probably not," Kelly said. "But I know that's probably not going to matter to her. I think she's such a devoted public servant that she's going to come out of this and be more resolved to fix things, to make things better for people."
Kelly has made sure to keep track of every gift, every message, every act of generosity from the people of Tucson, knowing that his wife will want to handwrite thank you letters.
"You know, she has Tombstone, Arizona in her district ... the town that's too tough to die," Kelly told Sawyer. "Gabrielle Giffords is too tough to let this beat her."