Humans have long pondered the question of how life on Earth came to be. How did the vast diversity of life we know today begin out of the atoms and molecules present on early Earth? There are a number of theories that aim to explain how this might have occurred, but one theory stands out from the rest, the idea that the seed of life came from outer space; the theory of panspermia.
How could this be possible? If humans can’t survive in outer space without an enormous amount of specialized equipment, how could primitive life? When most people think of life, they think of people, mammals, fish, insects, or plants, things that require sunlight and water for survival. Not all life fits into this category, though. Some organisms thrive in incredibly hot springs, deep-sea vents with no sunlight, and even highly acidic environments. These organisms are called extremophiles. If life can exist in such extreme conditions on Earth, maybe it could survive the harsh conditions of other planets or even a trip on an asteroid. It’s possible that life didn’t arise on Earth at all. Maybe it came from space.
Panspermia proposes that early life was ejected from other planets by collisions with asteroids, meteoroids, or comets. Life is believed to have developed billions of years ago during the period on Earth called the Late Heavy Bombardment where the planet was being impacted very frequently by asteroids and other Solar System bodies. If primitive life existed on Earth during this time, it would likely have been repeatedly sterilized by these collisions. Scientists who favor the panspermia theory use this as evidence that life must have first developed somewhere outside Earth and was then delivered to it by one of these impacts.
Another piece of evidence for the panspermia theory is the Murchison meteorite. It landed in Australia in 1969 and after being examined was shown to contain an abundance of amino acids and other organic material, material essential in forming life. Other experiments show that these amino acids are indeed capable of withstanding the pressures of an asteroid impact and that these unique conditions could have even caused them to form peptides, which form proteins, which are essential to the formation of cells.
Panspermia doesn’t have all the answers to the question of where life came from, though. It still doesn’t solve the problem of how life came to be from organic material, it just pushes that problem to another planet somewhere else in space. Even so, it’s exciting to think that maybe we aren’t the only life in the universe, even if it only exists in the form of tiny microbes. If the seeds of life are, or were at one point, shooting around space, it seems possible that they could have crashed into some planet out there quite a bit similar to Earth. Maybe that life grew and evolved to be something quite a bit similar to the beautiful array of life we have here on Earth.