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.

Hidden meanings

Why do judges use gavels? 10 objects that became symbols

We recognize certain symbols almost without thinking. Yet, when we stop to consider them, the object and the idea it represents can seem unrelated. As history unfolds, some unforeseen events created symbols that stuck until they became conventions. And now, when we see a gavel, we think of justice; commitment with a wedding ring, surrender with a white flag, and royalty with a shiny crown. Here is the story of how 10 everyday objects became universal symbols.

Even if you’ve never been in a real court, you've probably seen it in many movies: the judge slams the gavel, and the chaotic courtroom suddenly turns into complete silence. But why did a wooden hammer become a symbol of authority?

Centuries ago, English land auctioneers used small wooden hammers to signal that a property had officially sold. The sharp crack of wood cut through noisy auction halls, closing the sale. Then early American lawmakers noticed this practical gesture and brought it into legislative halls to manage loud debates and the judicial world. However, in real life, judges rarely use gavels.

A ring has no visible beginning or end. That shape creates a natural image of permanence and eternity. Ancient Egyptian couples used to twist river reeds into small rings to wear on their fingers. Later, in Ancient Roman marriages, the practice of giving a woman a metal band was connected with the betrothal ceremony.

The choice of the fourth finger on the left hand traces back to this same Roman era. Physicians of the time believed a vein ran directly from that finger to the heart, calling it the vena amoris, or "vein of love." Wearing a ring there was thought to form a physical link between the wearer's hand and their heart. Although anatomy has since shown no such vein exists, the tradition stuck and spread across cultures.

Christian weddings later made the exchange of rings a formal part of the vows. The object moved from one person to another, symbolizing a visible proof of a promise. Today, both spouses commonly wear rings, representing a commitment meant to endure.

In 69 AD, during the Battle of Cremona, Roman soldiers under the regime of Emperor Vitellius were surrounded by Vespasian's forces. The trapped troops were desperate to stop the slaughter, so they ripped off their clothes and waved them above the smoke. The bright clothes stood out against the mud and blood, and were a sign they weren’t advancing anymore.

That battlefield move became an international law in the Geneva Conventions of 1994. Since then, when a blank white sheet appears, it shows one of the sides has dropped their weapons and wants to talk. It's the universal shorthand for stepping out of the fight.

Warriors used headbands in the ancient world to keep their hair away from their eyes and also to spot their commander. Athletes sometimes received decorative bands after their victories, too. Royal families later began wearing fancier versions called diadems, which made their status easy to recognize.

Alexander the Great helped turn the diadem into a royal symbol after conquering Persia in the fourth century BC. As royals became wealthier, they covered metal circlets with precious stones. These crowns made monarchs stand out during ceremonies and public appearances, making them appear taller.

We have all wondered why the heart symbol looks nothing like the organ inside our chest. The real connection remains uncertain, though theories link the shape to ancient plants or early medical sketches. Long before that, Greek philosopher Aristotle claimed the heart was the body's emotional command center, describing it as a three-chambered organ rounded at the top and pointed at the bottom.

Medieval artists turned his influential descriptions into something people could actually see. In the 13th-century French manuscript Le Roman de la poire, a lover kneels and offers his pinecone-shaped heart to his lady. Similar depictions quickly spread across European art, smoothing the organ's edges into the familiar indented icon. Mass-printed Valentine’s Day cards later sealed the deal, reinforcing the heart shape as the universal sign of romantic devotion.

Fire is one of the basic elements of survival; centuries ago, people used torches to keep wild beasts away and to guide themselves in the dark. Later, in Ancient Greece, athletes ran relay races holding flaming torches, passing the light from runner to runner without letting the wind blow it out. Guarding the flame meant knowledge and community perseverance.

During the 18th century, thinkers of the Age of Enlightenment promoted science and individual rights over superstition and tyrannical rule, with light as a metaphor for human reason. When French sculptor Frédéric-Auguste Bartholdi designed the Statue of Liberty, he placed a torch in her right hand to guide arriving immigrants, turning the torch into a symbol of freedom too.

Today, the red carpet anticipates only one thing: someone important is coming. The oldest known literary reference to a red carpet we actually have appears in Agamemnon, a Greek tragedy first performed in 458 BC. In the play, Clytemnestra lays rich crimson fabrics before the king as he returns home. Agamemnon hesitates to walk on them, since he believes such an extravagant welcome should be reserved for the gods.

As red fabric remained expensive for centuries, red carpets had always had a strong connection with wealth and status. In 1902, the New York Central Railroad rolled out a crimson carpet for passengers boarding its luxurious 20th Century Limited train. And Hollywood adopted the custom in 1922 for the premiere of Robin Hood, and the Oscars introduced its red carpet in 1961.

Offering a handshake is the most natural greeting gesture nowadays. A popular explanation says that showing an empty hand proved you weren’t holding a weapon. Ancient Greek art also shows people clasping hands to express trust or confirm an agreement.

In the 17th century, English Quakers turned the handshake into what we know today. They preferred it to bows, which could reflect differences in social rank. Instead, shaking hands placed both people on equal terms, and the gesture gradually became a familiar sign of respect and trust.

Whenever a championship sports team or an honored guest visits town, you will often see the mayor hand them an oversized, designed key. But what do those giant keys represent? It is a powerful symbol of homecoming, trust, and honor.

The gesture traces back to the Middle Ages, when European cities were locked down behind stone walls and heavy iron gates every evening to keep out invaders. So, when a visiting merchant or allied leader was handed the latchkey of the city gate, it meant the guards trusted them to walk right in without an escort. Cities kept the tradition alive even though stone walls faded away.

You will often find tiny green olive sprigs on peace logos and treaty seals. At first sight, this makes no sense, but the answer traces back to the ancient Mediterranean. In those times, planting an olive grove was a huge act of faith. These trees grow at a crawl, needing decades of care before producing useful oil and food.

Whenever war broke out, invading armies targeted these groves first, destroying years of hard work in just a few seconds. So, thriving trees became proof of peaceful times and prosperity. Handing over the green olive sprig showed that it was time to rebuild.