Twin Astronauts Volunteer for Yearlong NASA Space Study

As part of an unprecedented study of zero gravity and weightlessness, identical twin astronauts have volunteered to take part in a yearlong NASA space project.

Retired astronaut Mark Kelly, 50, will stay home on Earth, while his brother Scott will be spending a year aboard the International Space Station beginning next March, planning to break the American record for longest time spent in space, the Associated Press (AP) reported.

"No second thoughts - I'm actually getting kind of excited about the whole idea as we get closer," Scott told the AP.

As for other people's reactions, he's heard everything from "'Oh, that would be really cool to be in space for a year' to 'What, are you out of your mind?'"

The goal of the experiment is for researchers to understand the effects of prolonged weightlessness, and being identical twins, Mark and Scott are likely to provide accurate analysis.

Both will undergo routine medical testing, but Scott volunteered for spinal taps, so he will have a pressure sensor drilled into his skull in order for the researchers to study the effect on vision impairment suffered by those partaking in long-term space missions - though NASA insists it is not necessary.

"As a test pilot, I like to push the envelope on things and, in this case, I feel like I'm maybe trying to push the envelope on data collection as well," Scott explained.

However, Mark draws the line at mimicking his brother's required daily two hours of exercise or his "crappy space station food" diet.

A retired Navy captain, Scott is no stranger to space travel. He spent five months in orbit from 2010-2011. At least this time around he will have company - 54-year-old Russian cosmonaut Mikhail Kornienko.

The Russians currently hold the record for longest time spent in orbit with their 14½-month mission back in 1994-95.

Researchers behind this study will analyze DNA and RNA replication, the visual impairment correlation with space flight, and the effect of weightlessness on the immune system of gut bacteria. NASA granted the researchers $1.5 million over three years for the project.