Mark Vande Hei orbited about the earth for nearly a year, for 355 days, a new record for an American astronaut, from April 9, 2021 to March 30, 2022. The record for the longest continuous stay in space is still held by a Russian cosmonaut, Valeri Vladimirovich Polyakov, whose 437 day stretch in space took him from January 1994 to March 1995.
Long stretches of time in space are a matter of great interest because, plainly, the human body did not evolve in zero-gravity conditions. It evolved with a skeleton and muscular system that keeps us upright against gravity’s pull, and with a sense of balance that records and preserves the distinction of “up” and “down.”
Hei spoke to this point in an interview soon after his return. “What is satisfying for me is that my body is part of the experiment,” he said. “I know people are going to have to go get data from me, and my contributions to that data will help people further explore.”
Strange New Worlds:
The estimates are that a round trip to Mars would involve at least 18 months in transit. Time spent on Mars itself would return the travelers at least briefly to an environment with a clear up/down orientation, but it would not be an earth-like interlude. The surface gravity on Mars is just a little more than one-third that on earth (38%). So terrestrial space programs want to do a good deal of study of the few such as Polyakov and Hei whose bodies may give them an idea of what happens to them in a prolonged period of micro-gravity.