Turns out being blown out of an airlock and turning into a meat ice block after succumbing to hypoxia isn't so bad. At least not when compared to the multitude of other deadly maladies that await you in the depths of space. Here are just a few ways that interplanetary exploration is conspiring to kill us all.
When stars collapse or supernova, the process throws off vast amounts of high-energy, charged nuclei, which become part of the Galactic Cosmic Ray (GCR) background radiation and diffuse into interstellar space. These nuclei are known as "HZE Particles" due to their high atomic number (Z, or the number of protons in the nucleus) and energy (E). While few in number, these HZE particles are both heavy and powerful enough to knock molecules out of joint and ionize biological tissue -- effectively scrambling an astronaut's DNA.
Not only do HZE particles produce chromosomal exchanges (gene swapping within a pair of homologous chromosomes) in the astronaut, which could significantly raise his chances of developing cancer, they have been shown to instigate genomic instability in fetuses as well, much like the after-effects of the bombing of Hiroshima. And those are just the effects we know about. Scientists still have very little data on the effects of HZE particles on a human's central nervous system, immune system and eyes -- especially in micro-gravity.
Corrosive Space Dust
When returning from a jaunt across the surface of our nearest celestial body, your first observation probably shouldn't be "[It] smells like gunpowder in here." But for Apollo astronauts Harrison "Jack" Schmitt and Gene Cernan aboard the Challenge Lunar Module in 1972, it did.
The source of the strange smell was moon dust, tracked in from the Sea of Tranquility. Formed by a near constant bombardment of micrometeorite impacts against the Moon's surface, the grey soil is finely pulverized with the consistency of flour. It is some surprisingly nasty shit. It gets everywhere and is highly corrosive. Moon dust had already infiltrated their suits and jammed the limb joints and "the dust was so abrasive that it actually wore through three layers of Kevlar-like material on Jack's boot," Professor Larry Taylor, Director of the Planetary Geosciences Institute at the University of Tennessee, told the Soil Science Society of America.
The crew breathed free-floating moon dust for their entire journey back to Earth. Schmitt suffered from mild congestion and what he described as "lunar hay fever" but the effects lasted less than a day. He was lucky because, as NASA scientists have since learned, Moon dust closely resembles silica dust at the microscopic level. Silica dust is not something you want to inhale; it causes silicosis, or "stone-grinder's disease".
Silicosis was first described during the Great Depression after it killed hundreds of miners working the Hawk's Nest Tunnel through Gauley Mountain in West Virginia. Just a few months of exposure to the freshly cut quartz dust killed them in just five years.
"It was one of the biggest occupational-health disasters in US history," Russell Kerschmann, a pathologist at Aames Research centre said. "You could eat it and not get sick," he continued. "But when quartz is freshly ground into dust particles smaller than 10 microns and breathed into the lungs, they can embed themselves deeply into the tiny alveolar sacs and ducts where oxygen and carbon dioxide gases are exchanged." Mucous can't dislodge the particles, and their sharp edges kill white blood cells that attempt to devour them. The patient eventually suffocates due to pneumonia-like fluid build-up in the lungs. Silicosis killed an estimated 16,000 people worldwide between 1968 and 2002.
Even worse: Mars dust. Not only does it have the same consistency of moon dust, it's also comprised in large part of iron oxide, a strong natural oxidiser on par with lye that burns through organic materials like rubber, plastic and human flesh. A dust devil on the Martian surface would likely eat through a space suit -- and most of the astronaut inside. It could very well be toxic too. "If you get Martian soil on your skin, it will leave burn marks," hypothesised University of Colorado engineering professor Stein Sture. "We don't know for sure how strong it is, but it could be pretty vicious."
The Space Junk Minefield
Between the US and Russia, we've launched objects into orbit more than four thousand times, roughly one new satellite or spacecraft every month. The problem is everything that made it beyond our atmosphere is still sitting right where we left it -- from the broken bits of failed satellites to shed spacecraft and rocket components like nuts, screws, paint, the 400 million needle-sized antenna the USAF launched in 1963 to reflect radio signals. And it's not just sitting there serenely, this stuff is whizzing about at 27,000km/h, ready to tear through a spacesuit, spaceship or even space station.
Today, there is roughly 5000 tonnes of space junk orbiting our planet (not including the constant waves of micrometeorites the burn up in the atmosphere). We know about the 600,000 bits bigger than a centimetre -- spacecraft can't deflect items that large so we have to track them using radar apertures originally designed to watch for incoming Soviet missile strikes. But even items below that threshold are capable of disabling a craft -- as a cloud of space dust did to Mariner 4 in 1967. And while strikes by objects bigger than that are rare, they are not unheard of. In 1986 a piece of space junk dented the interior wall of the Mir space station's crew compartment. NASA estimates that for every decade that the ISS remains aloft, its chances of being struck by -- and destroyed -- by space junk jumps 20 per cent.
The human body is a testament to our species' environmental adaptability. Even in the micro-gravity of interplanetary space, our bodies quickly adjust to the conditions -- bones and muscles that once had to support our weight and power our movements against the ubiquitous downward force of gravity will quickly atrophy. Who needs legs when you can float? Muscles, both skeletal and cardiac, may lose up to a fifth of their mass per week in space. Bone loses one to two per cent of its original density per month, up to an estimated 60 per cent overall loss.
"The magnitude of this [effect] has led NASA to consider bone loss an inherent risk of extended space flights," says Dr. Jay Shapiro, team leader for bone studies at the National Space Biomedical Research Institute said in a press statement. What's more, the calcium shed from your bones collects in the kidneys, often creating kidney stones. This happened to 14 American astronauts between 2001 and 2006 after returning from missions. On an extended voyage to, say, Mars, the development of a stone could not only incapacitate a crew member (as you are literally pissing sharp rocks) but were they to develop in both kidneys and block urine flow, it could kill him.
Blood too is affected by micro-gravity climates. The relative blood pressure differences present on Earth due to gravity (200mmHg at the feet, 70mmHg in the brain) are normalised in space (your blood pressure equalizes to 100mmHg throughout) which causes your circulatory system to freak out, and dump fluids -- as much as 22 per cent of your total blood volume, pissed away in two to three days. "If you have less blood," said Dr. Victor Schneider, a research medical officer at NASA headquarters, "then your heart doesn't need to pump as hard. It's going to atrophy."
Two broken legs and a heart attack -- welcome home, space man.