Did We Just Contaminate the Moon?

The moon is a dusty, dry, airless environment with no life… up until this past April, when we added an invasive species from another planet.

Image for post
The Moon. Orbiting around us, empty of life… or is it?

This past April, Israel had a bad day.

On April 11, 2019, an Israeli-based company called SpaceIL attempted to land a small robotic lander, named Beresheet, on the moon. As the lander descended towards the moon’s surface, however, its engine unexpectedly stopped firing — and without the engine to continue slowing its descent, the craft crashed into the surface and was destroyed.

However, when it crashed, the lander may have distributed microscopic creatures from Earth, called tardigrades, across the lunar surface. Tardigrades, sometimes referred to as “water bears”, are widely known for their ability to withstand extreme conditions — including extremely high and low pressures, high radiation levels, air deprivation, dehydration, and starvation.

The story of how the tardigrades even made it onto the spacecraft in the first place is fascinating — but do they stand a chance of surviving on the moon?

How Did Tardigrades Make It Into Space?

Image for post
A scanning electron microscope image of a tardigrade. In real life, it’s about half the size of a grain of salt.

Tardigrades are found around the globe; their extreme resilience makes it easy for them to survive in almost every environment, from rainforests to the Antarctic to the deep sea floor. First described in 1773, they mostly eat plants and bacteria, although some larger species may prey upon smaller tardigrades. They’re incredibly ancient; their resistance to most methods of elimination has helped them survive through mass extinctions. They were originally named kleiner Wasserbär, or “little water bear” in German, but were later named Tardigradum, for “slow walker”.

The inclusion of tardigrades on Beresheet’s cargo manifest was not recorded, and even SpaceIL’s own engineers didn’t know that the tiny animals were there.

Image for post
A “water bear”, but definitely not a tardigrade.

Interestingly, tardigrades have also been used in previous space research; they are the first animal that has been able to survive exposure to the hard vacuum of outer space. In 2007, they were exposed to space’s vacuum in low Earth orbit for 10 days, either with or without UV shielding. Among the tardigrades exposed to the vacuum with UV shielding, approximately two-thirds (68%) of the animals survived, although they showed increased mortality.

A container of tardigrades was placed on Beresheet, which is how they traveled to the moon. However, the inclusion of tardigrades on Beresheet’s cargo manifest was not recorded, and even SpaceIL’s own engineers didn’t know that the tiny animals were there.

How did this mistake happen?

A Last-Minute Addition From a U.S. Nonprofit

A U.S.-based nonprofit called the Arch Mission Foundation had previously received permission from SpaceIL to add a “lunar library” to their lander. This lunar library was a digital file containing 30 million pages of human history and discoveries, encoded on a physical storage disk the approximate size of a DVD.

When the Arch Mission Foundation went to add this lunar library to Beresheet lander, however, they made a last-minute switch. Nova Spivack, the co-founder of the Arch Mission Foundation, instead placed a small epoxy-filled container on the lander. Embedded inside the container were tardigrades, dehydrated and in induced hibernation.

Spivack originally planned to inform the world about his last-minute swap when the lander successfully touched down on the Moon’s surface. The crash initially derailed his plans… up until he and colleagues did the math and determined that the lunar library — and the organisms enclosed within — likely survived the crash and remained intact.

Spivack has happily declared himself to be the “first space pirate”, and as there are no official laws preventing the transfer of biological material to the Moon (China’s lander that recently touched down successfully on the dark side of the Moon carried a sealed container with several organisms, including cotton seeds, fruit flies, and yeast), he’s not in serious legal trouble. Spivack may, however, have violated the Outer Space Treaty, a series of loose guidelines that state that nations should oversee all activities in space conducted by non-government entities.

But what about the tardigrades? Are they about to run rampant across the lunar surface?

Fear Not, The Moon Won’t Become Tardigrade-Occupied Territory

Even if the tardigrades survived the Beresheet crash landing, scientists are in consensus that they won’t be likely to take over the moon. The reason boils down to the difference between “surviving” and “thriving”.

As noted previously, tardigrades are able to survive incredibly harsh conditions. They survive these conditions, however, by entering a state of suspended animation, or hibernation. They can remain in hibernation for many years, only emerging when they sense fresh water, which generally also brings plant or bacteria for them to eat.

On the Moon, however, there’s a distinct lack of water — and that’s not something likely to change in the near future.

Image for post
The best way to wake up a sleeping tardigrade.

Without water, the tardigrades will likely remain in suspended hibernation — and over time, they will eventually succumb to UV-induced radiation damage (the same type of damage that proved most lethal to the space-exposed tardigrades in the 2007 experiments). Even if the Arch Mission Foundation dispenses a couple bottles of water on the next Moon mission, there likely won’t be any remaining tardigrades left to revive.

The Moon’s harsh conditions have proved fatal for a number of other organisms sent to its surface. The cotton seeds that China sent on their recent lunar lander germinated and sprouted — but as soon as the scientists turned off the heater, the tiny little seedlings froze to death.

In fact, if there is any life at all on the Moon, it’s been there for more than half a century — in bags left behind by astronauts on their Apollo 11 visit.

When the Apollo 11 astronauts spent three days on the Moon’s surface in their lunar lander, they still had normal body functions — including defecation. To use simple terms, they pooped in bags. For weight concerns, those bags were left behind on the Moon’s surface — and human waste is made up mostly of bacteria. If there’s any life at all on the moon, it’s in those bags.

After fifty years, being exposed to above-boiling temperatures during the day and freezing cold temperatures at night, it’s overwhelmingly likely that all of the microbes in these poop bags are dead. If the bags remained sealed to trap in moisture, and the microbes were able to evolve tolerance to these extreme temperatures, however, there’s a chance that some may still be alive, growing in their tiny, enclosed habitats on the moon.

Tardigrades aren’t the first organism to make it to the Moon’s surface, but they’re one of the first to travel there secretly, launched in an unauthorized breach of protocol and distributed by a crash landing. Unfortunately, they’re not likely to survive for long, and certainly won’t thrive and take over the Moon’s surface.

Even so, their unauthorized transport to the Moon’s surface is likely to start a larger discussion about what protocols companies, governments, and individuals need to follow when transporting life to another planet. We’ve already sent microbes to Mars, although it’s unlikely that they survived. Still, we should hold a planned discussion before we intentionally start sending water bears off to other planets.

Sam Westreich holds his PhD in genetics, focusing on methods for studying the gut-associated microbiome. He currently works at a bioinformatics-focused startup in Silicon Valley. Follow on Medium, or on Twitter at @swestreich.

Have a microbiome-related question? Comment to suggest a topic for my next story. Or check out this related story:

Written by

PhD in genetics, bioinformatician, scientist at a Silicon Valley startup. Microbiome is the secret of biology that we’ve overlooked.

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store