Successful candidates have to fit in with Nasa's astronaut corps and live happily with them in a craft hurtling through the vacuum of space at 280,000km/h.
"Therefore, the most frequent bit of advice I've gotten from those associated with the programme is 'just be yourself'."
After Nasa has completed the interviews, it will trim the field down to around 50 finalists, who will undergo a week or more of rigorous tests early next year.
Next June, the successful eight-to-14 applicants will be picked for the Astronaut Candidate Class of 2017, reporting for duty just over a month later.
"It would be the most amazing dream come true to be chosen as one of the lucky eight-to-14, but so far the journey has been the reward, with the support and inspiration of such an incredible community surrounding me and cheering me on," she said.
She dreamed of one day becoming an astronaut -- but never thought it could be an actual career choice until a friend posted details about the programme on Facebook last year and she found she met all the basic requirements.
"My heart rate jumped up pretty high just contemplating the opportunity of getting to perform cutting-edge science ... so I started the application right then and there while eating my brekkie."
She later felt "completely humbled" to be invited for the initial interview.
Kessans has had plenty of adventure in her 33 years, including spending 16 hours clinging to a capsized rowboat in the Atlantic Ocean during a 3000-mile race in 2006 and then coming back to set a world record for rowing across the Atlantic in 2008.
Outside the lab, she kayaks, bikes, runs and explores New Zealand's natural wonders.
Kessans, who arrived in New Zealand in 2012 from Arizona State University, works in a research group developing compounds in fungus for use in medicine and agriculture -- something she feels would translate well to long-duration space missions.
"I thought I'd only be here in New Zealand for a post-doc, then I just fell in love with the country, got my permanent residency and, barring a job offer from Nasa, I'll probably stay here for a little bit."