Scientists have been trying to understand what all harms are caused to a human body in zero-gravity. NASA has plans to send humans on Mars by the 2030s and that is why it holds a significant importance for it to develop ways that can enable humans to avoid health risks because of space travel.

It is a known fact that the average human being consists of 60% water and body fluid moves upward in the chest and head when in outer space. It makes the legs weak and increases the pressure inside the skull.

The above mentioned problems are relatively new than the ones that have been discussed in the past. Brittling of bone and eating and sleeping deficiencies are some of the examples.

The longest stay in space by a human has been 438 days between 1994 and 1995 by Dr. Valery Polyakov of Russia. The mission being planned by NASA will require crew members to spend about three years on Mars. There are two other private organizations that have invited people to go on a one way trip to Mars without considering the known and unknown health risks crew members may face.

Dr. Michael R. Barratt (a NASA astronaut and physician) and Dr. Robert B. Thirsk (a Canadian astronaut and physician) performed eye tests on each other in 2009 during their six-month stay on the International Space Station.

They had to do so because of problem with their eyesight. They both discovered farsightedness as well as swelling in their optical nerves and damage to their retina.

NASA has made an announcement that operations at the International Space Station will be continued until 2024 to allow additional medical research.