The vacuum of space is an extreme environment, vastly different from Earth’s protective atmosphere. This article explores the scientific realities of what happens to the human body when exposed to the vacuum of space, examining the immediate, short-term, and longer-term effects.
The Immediate Impact of Vacuum
Exposure to the vacuum of space triggers rapid physiological changes. Air is immediately pulled from the lungs due to the extreme pressure differential, making it dangerous to hold one’s breath. This rapid decompression is followed by ebullism, the boiling of bodily fluids. Ebullism occurs because the low pressure in space causes the boiling point of liquids to drop to body temperature.
While blood within the circulatory system largely remains liquid due to internal pressure, water in soft tissues, saliva, and the surface of the eyes will vaporize and expand. This causes soft tissues to swell to about twice their normal size. Within 10 to 15 seconds, rapid oxygen depletion in the blood leads to unconsciousness. A NASA test subject reported feeling saliva boil before losing consciousness after 14 seconds.
Sensory functions, such as hearing and vision, can also be affected by oxygen deprivation. While significant pain is not typically reported beyond initial sensations, the lack of oxygen quickly renders a person unresponsive.
Dispelling Common Misconceptions
Popular culture often depicts inaccurate scenarios of human exposure to space. A common myth is that the human body will explode when exposed to a vacuum. While the body swells significantly due to ebullism, skin and other tissues are elastic enough to contain the expansion, preventing rupture. The internal pressure of the circulatory system also helps prevent blood vessels from bursting.
Another misconception is that a body in space would instantly freeze solid. Although space is extremely cold, the vacuum is a poor conductor of heat. Heat transfer in space primarily occurs through radiation, a much slower process than conduction or convection. Therefore, a body would not freeze instantly; other physiological effects occur much more quickly.
While some exposed fluids might undergo rapid evaporative cooling, the overall body temperature would decrease gradually over a much longer period. Oxygen deprivation and ebullism would incapacitate a person long before freezing became a primary concern. These myths often sensationalize the dangers, obscuring the actual consequences.
Beyond the Initial Shock: Longer-Term Effects
If exposure to the vacuum were to continue beyond unconsciousness, additional effects would manifest. Freezing would eventually occur, but it would be a slow process, taking hours as the body’s remaining water sublimates and heat radiates into the cold vacuum. Solar and cosmic radiation pose an immediate and severe danger.
Space radiation can cause significant cellular damage, increasing the risk of cancer and degenerative diseases. Acute radiation sickness could also occur from high levels of exposure, leading to severe health effects or death. Additionally, the body would slowly dehydrate as water continues to sublimate from tissues into the vacuum.
The Crucial Role of Spacesuits
Spacesuits are complex personal spacecraft designed to counteract the extreme conditions of space, enabling human survival. A primary function is to maintain a stable internal pressure, preventing ebullism and swelling. This pressurized environment keeps bodily fluids in a liquid state.
Spacesuits also provide a continuous supply of breathable oxygen and remove exhaled carbon dioxide. Temperature regulation is another aspect, as suits protect against extreme temperature fluctuations. Spacesuits also offer protection against harmful ultraviolet and particle radiation. They also protect against micrometeoroids.