NASA has been planning on sending people to the moon once again, as well as further space travel for humans and hopefully reach Mars in a few years. But with the discovery from a NASA research, will the space agency continue with their plan?

According to Daily Express, a recent NASA study has revealed that prolonged exposure to zero gravity can affect the blood flow of an astronaut's upper body.

The study was done on 11 healthy astronauts, consisting of two females and nine males of around 46 years old and have stayed an average length of six months aboard the International Space Station or the ISS.

For the test, these astronauts had their left jugular veins—the blood vessel which is responsible for draining blood from the brain, neck, face—monitored through ultrasound scanning.

The tests were done 50 days into the flight, then 150 days into the trip, and finally, after 40 days of returning home to Earth.

What the study revealed is that seven out of those 11 astronauts showed signs of stalled or reversed blood flow, specifically in the left internal jugular veins—something that can block the blood vessel and could severely impact an astronaut's health.

In worst-case scenarios, it can even lead to their death.

Long duration space travel in zero G is deadly, not mention exposure to cosmic rays. So much for all those Martian colony fantasies. You either have to generate artificial gravity, like spinning the crew vehicle around a central axis, or you have to accelerate at 1G, both of which are technically problematic. We have to think way outside the box and come up with propulsion method that gets us where we want to go very, very fast. Extremely long distance human space travel must be ultra-rapid transit in order to be survivable. To read more, click here.