Harvard’s Avi Loeb offered his latest speculation about humanity’s potential extraterrestrial origins during an appearance on the Joe Rogan Experience. The astronomer suggested that life on Earth might actually trace back to the Red Planet, transported here through cosmic mechanisms after Mars lost its ability to sustain life.
Loeb explained that the idea isn’t pure science fiction — it’s rooted in what we currently understand about the early solar system. Mars, he noted, may have once been the more habitable world of the two.
“Mars could have cooled faster than the Earth,” he said, pointing out that its smaller size means it loses heat more rapidly. That early cooling could have allowed rivers, lakes, and even oceans of liquid water to form long before Earth settled into a stable environment fit for life.
According to Loeb, this creates a cosmic twist: instead of Earth being the birthplace of biology, the origins of life might lie on our planetary neighbor. As he put it, “Life may have started on Mars, actually… because it had rivers, lakes, oceans of water, and it could have been actually delivered to Earth.”
This theory falls under a concept called panspermia — the idea that life can travel between planets via meteors or other cosmic material. Mars was bombarded with asteroids billions of years ago, just like Earth. When large rocks strike a planet with enough force, shards of its surface can be ejected into space. Some of those fragments could eventually crash onto another world while protecting microbial stowaways deep inside.
Loeb imagines those microscopic travelers as the first interplanetary explorers: “There were tiny astronauts inside the rocks that were chipped off the surface of Mars that arrived to Earth and seeded the Earth with life as we know it.” In other words, long before humanity dreams of sending missions to Mars, Mars may have sent life here first.
To determine whether this wild possibility might actually be true, Loeb emphasized the need for Mars sample return missions — a major goal for NASA in the coming decade.
While current rover evidence suggests Mars once had a climate supportive of life, any biosignatures found in Martian rocks remain inconclusive. “We need to bring a sample back to Earth so that in our laboratories, we can do isotope analysis and make sure that whatever signatures we see on the rocks… do look as if they were made by microbes,” Loeb explained.
If scientists eventually find fossilized microbes, we could be forced to face a transformative revelation: we are Martians. It would mean our distant ancestors survived ejection from their original world, endured a harsh voyage through space, and restarted life on a fresh planet.
As Loeb put it, heading to the Red Planet “might be the second trip around — we might be going back to our childhood home.”c consensus.