Whitson, who is now the oldest and most experienced woman to conduct a spacewalk, promptly reported the incident to Mission Control, which is now tracking the 1.5 meter (5 foot), 8 kg (18 pound) object as it floats in space.
The spacewalk formally began at 7.29 am (4.59 pm IST) when Whitson and her NASA colleague Shane Kimbrough switched their spacesuits to battery power before venturing outside the airlock and into the vacuum of space.
After 4 hours and 23 minutes, Whitson surpassed the existing record for the cumulative time a female astronaut has spent spacewalking, held by NASA astronaut Suni Williams. An important piece of micrometeorite shielding was lost during the spacewalk.
Astronauts at the International Space Station were on a spacewalk when a large debris shield got away.
The agency didn't explain exactly how the part was lost or misplaced, but it's been made abundantly clear that it is no longer on the space station.
"Shane, thank you for the words", astronaut Anne McClain replied from mission control at the Johnson Space Center. She is now on her third visit to the ISS and has spent over 500 days in space-yet another record for an American spacewoman.
A team from the Mission Control Center at NASA's Johnson Space Center in Houston devised a plan for the astronauts to finish covering the port with the PMA-3 cover Whitson removed earlier in the day. She accumulated enough spacewalking time to take the place of Sunita Williams.
Active on her Twitter account, @AstroPeggy, Whitson often writes about how research at the space station relates to everyday life, and how she travels the world as part of her astronaut training.
She is scheduled to return to Earth in June but could stay deployed until September.
Peggy Whitson acheived a record of being the oldest spacewoman with the highest number of spacewalks. NASA is hoping she can return to Earth then on an extra seat in the Russian Soyuz spacecraft.
This will be a six-and-a-half-hour spacewalk.
They quickly laid things on the floor and devised a way for the astronauts to use a different piece of cloth and wire ties as a substitute for the lost shield.