The Mighty Tardigrades: The Indestructible Creatures That Could Colonize the Moon

Friday - March 8 2024, 04:21 UTC - 8 months ago

In 2019, the unmanned space probe Beresheet carrying tardigrades crashed on the moon. These microscopic creatures are known for their ability to survive in extreme environments and may have contaminated the moon. Tardigrades can shut down their metabolism and reproduce in various ways, making them resilient against conditions on Earth and potentially on new environments like the moon.

Just over five years ago, on February 22, 2019, an unmanned space probe was placed in orbit around the moon. Named Beresheet and built by SpaceIL and Israel Aerospace Industries, it was intended to be the first private spacecraft to perform a soft landing. Among the probe’s payload were tardigrades, renowned for their ability to survive in even the harshest climates.

The mission ran into trouble from the start, with the failure of "star tracker" cameras intended to determine the spacecraft’s orientation and thus properly control its motors. Budgetary limitations had imposed a pared-down design, and while the command center was able to work around some problems, things got even trickier on April 11, the day of the landing.

On the way to the moon the spacecraft had been traveling at high speed, and it needed to be slowed way down to make a soft landing. Unfortunately during the braking maneuver a gyroscope failed, blocking the primary engine. At an altitude of 150 meters, Beresheet was still moving at 500 kilometers per hour, far too fast to be stopped in time. The impact was violent—the probe shattered, and its remains were scattered over a distance of around a hundred meters. We know this because the site was photographed by NASA’s LRO (Lunar Reconnaissance Orbiter) satellite on April 22.

So, what happened to the tardigrades that were traveling on the probe? Given their remarkable abilities to survive situations that would kill pretty much any other animal, could they have contaminated the moon? Worse, might they be able to reproduce and colonize it? .

Tardigrades are microscopic animals that measure less than a millimeter in length. All have neurons, a mouth opening at the end of a retractable proboscis, an intestine containing a microbiota and four pairs of non-articulated legs ending in claws, and most have two eyes. As small as they are, they share a common ancestor with arthropods such as insects and arachnids.

Most tardigrades live in aquatic environments, but they can be found in any environment, even urban ones. Emmanuelle Delagoutte, a researcher at the French National Center for Scientific Research (CNRS), collects them in the mosses and lichens of the Jardin des Plantes in Paris. To be active, feed on microalgae such as chlorella, and move, grow, and reproduce, tardigrades need to be surrounded by a film of water. They reproduce sexually or asexually via parthenogenesis (from an unfertilized egg) or even hermaphroditism, when an individual (which possesses both male and female gametes) self-fertilizes. Once the egg has hatched, the active life of a tardigrade lasts from 3 to 30 months. A total of 1,265 species have been described, including two fossils.

Tardigrades are famous for their resistance to conditions that exist neither on Earth nor on the moon. They can shut down their metabolism by losing up to 95 percent of their body water. Some species synthesize a sugar, trehalose, that acts as an antifreeze, while others synthesize proteins that are thought to incorporate cellular constituents into an amorphous "glassy" network that offers resistance against stress and desiccation. This makes it almost impossible to vaporize them without completely smashing them.