Reason behind Sunita Williams' gray hair decoded after NASA astronaut was left stranded 9 months in space

WASHINGTON, DC: After months of trepidation, NASA astronauts -- Sunita Williams, 59, and Barry “Butch” Wilmore, 62 -- finally returned to Earth on Tuesday, March 18. 

While the pair’s return after completing a nine-month orbit in space brought relief to their family members and fans, a few onlookers spotted a full head of gray hair on Williams’ head. 

Though a section of fans quipped that it was due to a shortage of hair dye in the ISS, as reported by The Mirror, staying in space for more time than Williams may have bargained for might also have been one of the contributing factors as well.

The reason behind Sunita Williams’ gray hair

As of now, no scientific research has connected the graying of hair with space travel. Though not in so many words, NASA has suggested that spending time in space may cause "significant physiological changes."

In a social media post, the National Aeronautics and Space Administration wrote, "Imagine if all of your physiological changes were hyper-accelerated so that you passed through life cycles in weeks as opposed to decades," referring to its work to understand how human physiology is affected by time in space. 

The federal agency noted further, "You'd be able to grow a beard overnight or your hair might begin graying in a matter of days or maybe menopause would come knocking by next weekend.”

The outlet further revealed that a 2016 study revealed the effect of spaceflight on human hair specifically. 

The study from the National Institute of Health said that "spaceflight alters human hair follicle gene expression," adding space travel can hinder "cell proliferation" in hair follicles, leading to “unregulated” growth, and potential hair loss. 

US Navy nuclear technician cites lack of hair dye to be the cause of Sunita Williams' gray hair

As reported by the New York Post, the astronauts are feared to develop several symptoms including, dizziness, balance problems, weak hearts, bone-density loss and fluid build-up, apart from the noticeable change in hair color. 

Reflecting on the change, Emily Carney, a former US Navy nuclear technician and space historian, explained plainly that the lack of hair dye and makeup mirror is responsible for the astronaut's changed look. 

Taking to her Threads account, Carney wrote, “A few have asked me why Sunita Williams has grey hair and looks ‘tired’ coming back home from space,” before adding, "This is because in space there’s no hair dye or makeup mirror at your disposal.”

Following their 286-days long stint at the ISS, the astronauts will now be going through an acclimatization process to re-adapt to Earth's condition, reports the outlet.