How long stranded NASA astronauts could survive on ISS if all life on Earth was destroyed

Here is how long an astronaut could survive on the International Space Station if the rest of humanity ceased to exist.

The never-ending saga to bring stranded NASA astronauts Butch Wilmore and Suni Williams home from the space has hit another roadblock, after it was confirmed yesterday that the mission to retrieve the pair had been delayed once again.

They were only meant to be there for eight days, but have been on the ISS for nine months.

Following the news of delay, inquiring minds have begun to wonder how long an astronaut would be able to survive on the ISS, leading to today's morbid scenario — how long could an astronaut survive in space in the event of a global disaster?

Without Earth, how long could astronauts survive on the International Space Station? (Getty Stock Images)

In our imaginary scenario, the Earth - and all living things on it - have been wiped out by a major extinction event while the seven astronauts on the ISS could do nothing but watch on.

Once the crew had come to terms with the loss of their loved ones and everything that's ever existed on our home planet, focus would likely turn to survival.

How long could an astronaut survive on the ISS if Earth was destroyed?

The grim subject was broached by YouTuber and educator Vsauce who explained that breathable oxygen is recycled on the station through electrolysis, while rationed food means they could last for around two years before going hungry, depending on when the last supply ship docked.

NASA previously stated that all food pinged into the cosmos must have a shelf-life of at least one year, although in this scenario we don't think expired food would be high on your list of concerns.

Astronauts on the ISS once had to go eight months without restocking food, water and other supplies after three successive supply missions failed, the space agency said. So there have been real scenarios where they've had to go for long periods without supplies from Earth.

However, food and air aren't the most pressing concerns. Although you'd likely argue whether or not there's a point to carrying on while knowing your ultimate fate.

So if lack of food or oxygen wouldn't kill our spacefaring explorers, what would?

Turns out it would be something called orbital decay.

According to Vsauce, the ISS could likely last for around 15 months before crashing into Earth, stating: "The first thing they would run out off... would be altitude."

The ISS orbits around 260 miles (418 km) above, but dips closer to the planet due to a combination of the Earth's gravitational pull and a low level of oxygen which slows the ship down.

However the ISS orbit is usually set back on course by periodic reboots from supply ships.

If Earth faced an extinction event then our astronauts wouldn't be too far behind (Getty Stock Images)

According to NASA's 2024 Space Station Transition Plan, the agency predicts the ISS would last for roughly 'roughly one-to-two years' without reboots before it burned up in the Earth's atmosphere, therefore making the YouTuber's prediction about right.

But this still doesn't answer the biggest question of our hypothetical scenario — would the astronauts even want to survive this long while knowing what awaited them?