If Life Traveled From Mars To Earth On A Rock, Who Are We? A number of scientists say evidence is building for the theory that life started on Mars. With potentially infinite possibilities for life to bloom in this vast universe, NPR's Scott Simon wonders what it means to be human.

If Life Traveled From Mars To Earth On A Rock, Who Are We?

If Life Traveled From Mars To Earth On A Rock, Who Are We?

  • Download
  • <iframe src="https://www.npr.org/player/embed/217236697/217511063" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

What if we're all from Mars? AFP/Getty Images hide caption

toggle caption
AFP/Getty Images

What if we're all from Mars?

AFP/Getty Images

We might be Martians.

This week Steven Benner, president of the Foundation for Applied Molecular Evolution, told the annual Goldschmidt Conference in Florence, Italy, that "the evidence seems to be building that we are actually all Martians; that life started on Mars and came to Earth on a rock."


There is a scientific phrase for this: panspermia, which sounds a little like a new pharmaceutical advertised during pro-football games. But it's the fact that when asteroids slam into planets, they send up showers of matter that can be sent soaring through space as meteorites and land on other planets.

An estimated one billion tons of rock have made it from Mars to Earth over the years. Because of orbital mechanics, that's been a one-way street. In the early days of creation, the climates of the two planets were apparently more alike than they are now, including substantial amounts of water on Mars.

Steven Benner and a number of other scientists now believe it's likely that our larger planet's greater gravity, warmer temperatures and magnetic field allowed minute organisms borne here from Mars to eventually evolve into the kinds of life we see around us now, from flowers, grass and Lake Michigan to gnats, elephants, and Miley Cyrus.

There are other scientists who find this thinking interesting but unconvincing. David Grinspoon, an astrobiologist from the Denver Museum of Nature and Science, told NBC that it's a "plausible story" but unproven. He believes it's just as possible that life emerged from Earth's own pre-biotic homebrew.

"I think chemists always think they know more than they know, because nature has a lot of possible pathways it can try," Grinspoon says.

Still, the notion that we might be Martians is the kind of bold, huge idea that might overturn your view of the world and set fires in your mind.

If we are not Earthlings, who are we?

Could the incalculably precious chemical reaction that led to the life we know on Earth — life that not only breathes and eats, but loves, laughs, knows that we will die, and even wonders why we're here — be truly accidental?

Or is the universe so vast, there are infinite possibilities for life to bloom? Is existence as routine and predictable as turning over a log to find a lot of ants?

I used to wonder if life on other planets glimpsed us and said, "Look at those funny Earthlings! They come in all different colors and shapes." But if we're from out there, too, it may remind us that we're not just one world — we're one universe. We are all aliens. The Martians are us.