Star Talk: Prolonged weightlessness affects astronauts in many ways
Do you wake up in the morning with a puffy face? When astronauts are in space, they have a puffy face all the time. Puffy face syndrome is just one of the many changes that happen to the human body in a zero gravity environment.
Humans are well-adapted to the surface gravity of Earth. However, living in the weightless environment of space for extended amounts of time can cause adverse effects on the human body.
Understanding the long-term consequences of weightlessness, and how to compensate for its effects, is important for astronauts spending several months on the International Space Station or for strategists planning an 18-month manned mission to Mars.
In a weightless environment or, more properly, a microgravity environment, astronauts are in orbit or free-fall around Earth. Under these conditions, they seem to be floating in space as the walls of the spacecraft move toward and away from them as fast as they fall toward and away from the walls.
Moving around the spacecraft no longer requires that astronauts use the large muscles and bones of the lower body that bear its weight against gravity. Consequently, there is a loss of bone and muscle mass. Bones start to become brittle and muscles begin to atrophy. The risk of bone fractures increases. Astronauts can lose as much bone mass in a month as a postmenopausal woman loses in a year.
Losing lower body strength is of great concern. Some astronauts are not able to walk once arriving back on Earth from extended space flights. In one case, it took an astronaut almost two years to regain his lost bone mass after returning. Since a flight to Mars will take the better part of a year, will astronauts collapse once they land on the surface of the Red Planet?
To compensate for the deteriorating effects of zero gravity on their muscles, astronauts maintain a rigorous, two-hour exercise regimen every day.
The International Space Station is equipped with two treadmills, a stationary bicycle and an “advanced resistive exercise device.” This machine enables astronauts to do various weight-lifting exercises. To avoid floating away while working out, the astronauts attach themselves to the training equipment with bungee cords.
Astronauts wear pants equipped with elastic bands to compress the leg bones to maintain and build bone strength. Along with osteoporosis medications, these techniques aid in slowing the loss of bone and the growth of new bone.
On Earth, gravity pulls bodily fluids downward to the lower parts of the body, especially the legs. Upon entering the microgravity environment of space, fluids immediately begin to redistribute more evenly throughout the body. More fluid in the upper part of the body manifests itself with bulging neck veins, sinus congestion and a general puffiness in the face (facial edema).
An overabundance of fluids in the chest causes the kidneys to increase fluid elimination. Over time, with little or no mechanical stress on the bones, more calcium is lost into the bloodstream; this in turn increases the risk of kidney stones.
Blood pressure in space is not maintained the same way it is on Earth because of the fluid shifts. This is a danger for astronauts returning from prolonged space flights.
Once out of orbit, fluids immediately begin to shift back to the lower body and some astronauts are unable to stand for more than ten minutes without assistance because of feeling light-headed.
Increased fluid in the cranium can increase pressure on the eyeballs, changing their shape and possible affecting vision. Tears cannot be shed in the weightless environment of space but stick together into a ball because of surface tension.
Calluses on the bottom of the feet slowly disappear from lack of use, leaving the skin soft. Astronauts also report changes in their sense of taste and tend to choose strong-tasting foods to compensate.
Long-term space flights can also have psychological effects, as astronauts are under public scrutiny and isolated from family and friends. Quality of sleep is poor because the light-to-dark cycle is about 90 minutes in an orbiting spacecraft and sleep can be interrupted by the demands of the mission. Fan noise is always present. Fans are always turning to keep the air in motion since in zero gravity air stagnates because convection cannot occur.
In the science of space medicine, NASA continues to study the health effects of weightlessness on astronauts to develop methods in which humans can live safely in the challenging environment of outer space.
Eulogy for a comet
As Thanksgiving neared, Comet ISON grew brighter and some of the local amateur astronomers began to see the comet with the naked eye (without binoculars or a telescope) in the east just before the first light of dawn. Within a few days of Thanksgiving, the comet was no longer observable as it moved into the morning twilight and closer to the sun.
Then at 2 p.m. on Thanksgiving Day, the comet passed less than a million miles above the sun’s surface, where it was exposed to the tremendously intense heat, radiation and extreme force of the gravity of the sun at that close distance.
Comet ISON, a small celestial ice ball only three miles across, did not survive; it was ripped apart by the sun. The ensuing rubble from this close solar encounter moved away from the sun and quickly dispersed into the solar system.
The demise of Comet ISON was recorded by the Solar and Heliospheric Observatory, a scientific satellite in orbit around the sun. This time-lapse video can be viewed at NASA’s Astronomy Picture of the Day for Nov. 30 (apod.nasa.gov/apod/ap131130.html).
Richard Monda is an astronomer living in the Capital Region.