Are We All Martians?— Panspermia and Our (Possibly) Extraterrestrial Origins. 

Where did life start on Earth? We have all been taught about the perfect conditions Earth has for life; it’s just the right distance from the Sun, has water and carbon, its constantly changing environment cycling energy to sustain life (American Museum of Natural History, n.d.). Ever since, we have been in pursuit to find life as complex as our own, sending out landers, rovers, and watching diligently on deep space telescopes— looking for alien life upon a planet beyond our galaxy. Had we ever thought about the possibility that the extraterrestrial life we had been looking for had been closer than we thought?

The panspermia hypothesis, suggests that lifeforms like bacteria had hitchhiked upon comets or asteroids, carrying inhabitants along the way and eventually ending up on Earth (Mortillaro 2020). NASA’s OSIRIS-REx and Japan’s Hayabusa2, over the years, brought asteroids samples to Earth, some containing the building blocks of life. This raises the question of whether these building blocks or even full lifeforms themselves were delivered onto Earth. Dr. Jason Dworkin, a project scientist on the OSIRIS-REx mission, says it is definitely plausible, as “Early Earth had a bombardment of material” (O’Callaghan 2026). The idea of Mars being the main source of this trans-planetary exchange stems from the fact that it once was potentially perfect for life with its large oceans (Mortillaro 2020).

Hypothetically, microbes within rocks could be protected from UV rays and survive space travel known as lithopanspermia. Researchers even believe microbes can survive space travel through a thick aggregate of bacteria to survive the conditions of space as well, known as massapanspermia. Now, if these life-forms successfully did manage to land and survive on another planet and reproduce, would require life to survive the space vacuum, temperature fluctuations, and space radiation (Sammicheli and Szanto 2020).

Figure 1: Image showing three stages of lithopanspermia from Mars to Earth (Meyer 2008).

To discover its plausibility, a group of Japanese scientists conducted an experiment on the International Space Station, discovering some bacteria can survive in space for up to 10 years. Starting in 2015, they used Deinococcal bacteria— a radiation tolerating bacteria in varying thicknesses outside the space station for one, two, and three years. In the end, bacteria larger than 0.5 mm all survived below the top layer. Now, researchers believe a colony larger than a millimetre can be shielded from space and even up to 10 if protected by rocks, giving both massapanspermia and  lithopanspermia credibility in their ability to transmit life (Mortillaro 2020)

​Now, our common belief of life only exists one time, in specific circumstances; if panspermia is possible, truly life would become a much more common thing than previously thought. Due to Mars and Earth coming closer together in orbit each year, Professor Akihiko Yamagishi—a key investigator of the study says it would allow for the transfer of bacteria or self-replicating RNA from Mars to seed Earth (Mortillaro 2020). Even back in 1996, scientists had found traces of microfossil bacteria inside a meteorite from Mars uncovered in Antarctica 10 years prior to its discovery, known as the Allan Hills 84001 (O’Callaghan 2026). Now, until we ultimately find proof of panspermia or really that Earth truly is a miracle, this information changes our perceptions of outer space. If Martians were once believed to be the work of Sci-Fi really exist, it may not require a trip across planets, but rather a glance in the mirror.

References

American Museum of Natural History. n.d. “Why is the Earth habitable? | AMNH.” American Museum of Natural History. Accessed September 21, 2026. https://www.amnh.org/exhibitions/permanent/planet-earth/why-is-the-earth-habitable.

Meyer, Cornelia. 2008. “Is there anybody out there? An ark of life.” Science in School. https://scienceinschool.org/article/2008/esasuccess/.

Mortillaro, Nicole. 2020. “Could life have started on Mars before coming to Earth? Possibly, new study suggests.” CBC. https://www.cbc.ca/news/science/mars-panspermia-1.5699671.

O’Callaghan, Jonathan. 2026. “Scientists are now seriously asking if humans were seeded by aliens. Here’s why.” BBC Science Focus Magazine. https://www.sciencefocus.com/space/humans-seeded-aliens-panspermia-2.

Sammicheli, Lucie, and Balazs Szanto. 2020. “Bacteria could survive the travel from Earth to Mars, and vice versa, when forming aggregates.” Frontiers. https://www.frontiersin.org/news/2020/08/26/bacteria-could-survive-the-travel-from-earth-to-mars-and-vice-versa-when-forming-aggregates.