Extreme challenges

What is the Kessler Syndrome? 10 serious threats astronauts face in space

Image: NASA Hubble Space Telescope

Space is the final frontier, but that hasn’t stopped humans from pushing beyond its boundaries. Space exploration, however, is fraught with danger. On Earth, we’re shielded from the cosmic hazards and extreme conditions that dominate the universe, but beyond our atmosphere, astronauts face a multitude of threats. From handling microgravity’s impact on the body to navigating the deadly vacuum, survival in space requires precision and discipline. Here are 10 essential things astronauts must do to stay alive—and continue their quest to explore the cosmos.

Image: Benjamin Recinos

A space suit is essential for survival beyond Earth’s atmosphere, providing protection from various hazards such as extreme temperatures, radiation, vacuum, and even space debris. The suit contains several layers, including thermal control and micrometeoroid shields, ensuring astronauts don’t freeze in the shadow of space or burn in direct sunlight. It also prevents depressurization effects by maintaining a stable internal atmosphere.

The suit also contains communication systems and a supply of oxygen, allowing astronauts to breathe and stay connected with their team during spacewalks. Without a suit, exposure to space would cause an astronaut to lose consciousness within seconds due to the lack of atmospheric pressure and oxygen deprivation.

Image: Joshua Chehov

As most people know, space lacks breathable oxygen. While oxygen is technically present beyond our atmosphere and elsewhere—ranking as the third most abundant element in the universe—its concentration in the vastness of space is so low that, for all practical purposes, it is equal to 0%. Thus, maintaining a sufficient oxygen supply is one of the greatest challenges astronauts face.

Fortunately, there are effective methods for generating oxygen to support long-duration missions. On the International Space Station (ISS), oxygen is produced through electrolysis, a process that splits water into oxygen and hydrogen. In the case of a system failure, astronauts can rely on emergency oxygen tanks, although these supplies are limited. Equally important is managing carbon dioxide levels. A process called carbon dioxide scrubbing is used to eliminate CO2, preventing suffocation.

Image: NASA

While there is no such thing as "zero gravity," the effects of Earth's gravity diminish the farther we travel from its sphere of influence. This near-weightless condition, known as microgravity, triggers immediate physiological changes in the human body. Without the gravitational pull that typically draws blood toward the legs, fluids shift upward, causing facial swelling and increased pressure behind the eyes. This can lead to a range of health issues, including impaired vision.

Over time, astronauts also face muscle atrophy and bone density loss, as their bodies no longer have to bear their own weight. To counteract this, astronauts must exercise daily with resistance machines, treadmills, and bikes. However, even with strict exercise regimens, muscle and bone recovery can take months once they return to Earth.

Image: NASA

While we may not always be aware of it, Earth's atmosphere and magnetic field provide essential protection against a range of invisible dangers found in deep space, with radiation being one of the most concerning. Even during a flight, passengers are exposed to elevated levels of radiation, roughly equivalent to a chest X-ray for every 10 hours spent in the air.

Astronauts, however, often operate beyond the protective layers of our planet, exposing them to even greater radiation levels. Spacecraft are equipped with radiation shields, but they can’t block all radiation. Astronauts can receive up to 10 times the radiation dosage they would on Earth, increasing their cancer risk in the long term. But the most dangerous radiation threat comes from solar flares. During these solar events, astronauts must take cover in specially shielded areas of their spacecraft.

Image: Kai Dahms

In space, every ounce of food and water must be carefully rationed. Thus, astronauts survive eating pre-packaged, freeze-dried meals that are both lightweight and rich in nutrients. They simply add water to rehydrate the meals before eating, ensuring they get enough calories to maintain energy levels. While it might not sound very appealing to live out of freeze-dried meals for months, astronauts also experience a noticeable reduction in taste due to the lack of gravity.

Drinking water presents its own set of challenges. Nothing can be wasted, so space stations designed for long-term habitation, like the International Space Station (ISS), often employ advanced filtration systems to recycle water from condensation, sweat, and even urine! Astronaut life isn’t all it’s cracked up to be, huh?

Image: NASA

Even with all their training, the deep isolation and confinement of space can significantly impact an astronaut’s mental health. Long missions far from Earth can lead to feelings of loneliness, anxiety, and depression. To deal with that, astronauts are encouraged to maintain a daily routine, exercise, and engage in team activities. Communication with loved ones back on Earth is also crucial for their emotional well-being.

Space agencies take mental health very seriously, conducting regular psychological assessments during missions. Studies have shown that astronauts on extended missions may experience a decline in cognitive abilities and an increase in stress levels—factors that can be critical in such a delicate environment, where mental clarity and emotional stability can be a matter of life or death.

Image: noe fornells

Despite the popular belief that it’s unforgivingly cold, space doesn’t have a temperature in the traditional sense—after all, it’s a vacuum. Instead, temperatures can shift dramatically, ranging from boiling hot to freezing cold, depending on exposure to the Sun. Astronauts rely on their suits and spacecraft systems to maintain a stable internal temperature. The suit’s liquid cooling garment, which contains a network of water-filled tubes, helps astronauts regulate their body temperature during spacewalks.

Inside the spacecraft, temperature control systems work to prevent the interior from becoming unbearably hot or cold. However, there have been instances where astronauts had to repair these systems themselves to avoid the dangers posed by extreme temperatures, which can fluctuate rapidly from 250°F to -250°F.

Image: Muha Ajjan

Ever wondered why most astronauts struggle to walk by themselves after returning to Earth from long missions? As we pointed out before, without the constant pull of gravity, muscles weaken very rapidly. In fact, astronauts can lose up to 20% of their muscle mass in just two weeks without exercise.

While it would be technically possible to maintain proper muscle mass through rigorous exercise, doing so would require significantly more time than it does on Earth. Astronauts lead extremely busy lives—every minute counts up there—leaving little time for anything beyond essential tasks. So, if you were thinking about heading to space to hit the gym, you might want to reconsider and stick to your local fitness center instead!

Image: NASA Hubble Space Telescope

Space debris, which includes everything from tiny meteoroids to fragments of defunct satellites and spent rocket parts, can travel at astonishing speeds of up to 17,500 mph! These high-speed projectiles can easily puncture spacecraft or damage equipment, putting astronauts' lives at serious risk.

The ISS is equipped with monitoring systems that detect nearby debris, allowing the station to perform evasive maneuvers when needed. However, this is far from a solved issue. Many scientists warn that if space pollution, much of which is produced by improper satellite disposal, is not addressed soon, it could lead to a cascading effect of collisions that would generate even more debris, and thus more collisions… you get the idea. This alarming scenario is known as Kessler Syndrome, and if left unchecked, it could threaten the safety and feasibility of future space exploration.

Image: National Cancer Institute

As if astronauts didn’t have enough going on already, space weakens the immune system, making astronauts more vulnerable to infections. This immunosuppression is caused by a mix of stress, microgravity, and increased radiation exposure. Studies have shown that astronauts’ white blood cells, which help fight infections, are less effective in space.

To make things worse, bacteria and viruses seem to behave differently out there, often becoming way more virulent than on Earth. Astronauts must be extra vigilant about hygiene, regularly disinfecting their living spaces and monitoring their health—not an easy task in the often cramped spaces where they must carry out their missions.

Real meanings for unreal beings

What does "wendigo" really mean? 12 mythical creatures’ names explained

Monsters, ghosts, and strange beasts have haunted stories for a very long time, but their names can be just as mysterious as the creatures themselves. Some are surprisingly literal, while others have traveled across languages, religions, and continents before reaching English. From a "knocking spirit" to a goblin hiding in the periodic table, here’s what the names of 12 famous mythical creatures really mean.

The word zombie has traveled almost as dramatically as the creature itself. English acquired it through Caribbean forms such as Haitian Creole zonbi, with deeper roots in African languages. Merriam-Webster compares it with Kimbundu nzúmbe, meaning "ghost."

The traditional Haitian concept also differs significantly from Hollywood's hordes of contagious undead. Zombies became associated with people supernaturally deprived of autonomy and restored to a form of life. The modern flesh-eating version is largely a product of later popular culture, which transformed both the creature and the image English speakers associate with its name.

The word wendigo comes from a family of related Algonquian words, including Ojibwe wiindigoo and Cree wīhtikōw. The Ojibwe People’s Dictionary describes wiindigoo as a winter cannibal monster associated with terrifying, insatiable hunger.

But its literal origin is surprisingly uncertain. The mysterious-sounding word fuels the image of a night monster from past times.

A banshee's famous cry sounds frightening enough, but her Irish name is much less sinister. Banshee comes from bean sí: bean means "woman," while sí refers to the supernatural beings traditionally associated with Ireland's ancient mounds.

That makes the name something like "woman of the fairy mound." And contrary to many movie versions, a banshee traditionally doesn't scream someone to death. Her mournful keening warns that a death is approaching, making her more of a supernatural messenger than an attacker.

Sometimes a monster's name tells you exactly what you're getting. Werewolf comes from Old English werwulf, combining wer, meaning "man," with wulf, meaning "wolf." In other words, the fearsome name basically means "man-wolf."

The interesting part is that wer was once an ordinary word for a male person before disappearing from everyday English. Meanwhile, the alternative lycanthrope reaches almost the same destination through Greek: lykos means "wolf," and anthrōpos means "human being."

Today, finding your doppelgänger might mean spotting somebody who looks uncannily like you. The German word is wonderfully straightforward: doppel means "double," while Gänger means "goer." English speakers began using doppelgänger during the 19th century.

Originally, however, this wasn't merely a word for two strangers who could pass for siblings. A doppelgänger could be an eerie supernatural counterpart of a living person. Over time, the ghostly implications faded, leaving us with a convenient, and much less alarming, word for a look-alike.

If a ghost spends the night knocking things around, German already has the perfect name for it. Poltergeist combines a verb meaning "to knock" or "make a racket" with Geist, meaning "spirit." Literally, it's essentially a "knocking spirit."

That explains why poltergeists differ from the stereotypical silent apparition floating down a hallway. Their calling card is physical commotion: bangs, mysterious noises, and moving objects.

Long before the golem became a legendary creature, its name appeared in the Hebrew Bible. In Psalm 139, the Hebrew golem refers to something unformed or unfinished, an intriguing origin for a being traditionally fashioned from lifeless material.

Jewish folklore eventually transformed the idea into an artificial humanlike figure, commonly created from clay and animated through sacred knowledge.

Here's a surprisingly gentle name for a decidedly ungentle monster. Chimera comes ultimately from Greek chimaira, meaning "she-goat." Yet the mythological Chimera was no ordinary farm animal: ancient accounts combined parts of a lion, goat, and serpent into one fire-breathing beast.

The hero Bellerophon eventually defeated it while riding Pegasus. Its bizarre mixture of incompatible parts proved linguistically durable. A chimera later came to mean an impossible fantasy, while modern biology uses the same word for an organism containing genetically distinct populations of cells.

The Minotaur's name is practically a miniature plot summary. Greek Minōtauros combines the name Minos with tauros, meaning "bull." The famous monster is therefore, quite literally, the "bull of Minos."

According to Greek mythology, King Minos had the creature confined inside the Labyrinth designed by Daedalus on Crete. Theseus eventually killed the Minotaur and found his way back with Ariadne's help.

Break apart hippogriff, and half the creature immediately appears. Its first element ultimately comes from Greek hippos, meaning "horse," joined to griffin.

Italian poet Ludovico Ariosto featured the hippogriff in Orlando Furioso, first published in 1516. He imagined the flying animal as the impossible offspring of a mare and a griffin. Modern fantasy fans may know the creature from Harry Potter, but hippogriffs had already been around for roughly five centuries.

Kobolds were mischievous spirits in German folklore, appearing around homes or underground. Another remarkable oddity is the fact that one of these creatures managed to sneak onto the periodic table.

The element cobalt takes its name from kobold. German miners used the term "supernatural" for troublesome ores that failed to produce the metals they expected and could contain dangerous arsenic compounds. In the 18th century, Swedish chemist Georg Brandt established cobalt as a distinct element.

The Kraken came into English from Scandinavian tradition, where stories described an enormous sea creature lurking beneath northern waters. English records the word by the mid-18th century, when European writers were spreading accounts of the supposedly gigantic beast.

Its name contains a neat grammatical surprise. Scandinavian kraken is related to krake, with the final -n functioning as a definite article, essentially "the krake." Later encounters with real giant squid offered a tantalizing possible explanation for some old sea-monster stories.