We have been making a synopsis of a book about the origins of life.
It seems possible that rocks with microbes in them have been travelling between planets and possibly between galaxies. What is the name of this theory?
The theory you’re referring to is known as “panspermia.” This hypothesis suggests that life exists throughout the Universe, distributed by space dust, meteoroids, asteroids, comets, planetoids, and potentially by spacecraft.
Do you have some examples of how this could happen?
- Lithopanspermia: Imagine a big rock from Mars, for example, gets hit by an asteroid and breaks off. If this rock had tiny life forms or their building blocks inside it, and it somehow landed on Earth, those life forms could start living here. The rock acts like a protective spaceship for these tiny life forms.
- Radiopanspermia: This one is about tiny life forms or their building blocks floating through space, pushed by light from stars. Think of it like tiny seeds blowing in the wind, but in this case, the “wind” is light from the sun or other stars pushing them through space.
- Directed Panspermia: This is a more science-fiction-like idea. It suggests that advanced aliens might have intentionally sent life to Earth. It’s like if someone planted a garden, but in this case, the garden is Earth, and the gardener is an alien civilization sending life to start here.
While panspermia is a fascinating hypothesis, it remains speculative and there is currently no direct evidence to support the theory. However, discoveries of extremophiles (organisms that can survive in extreme environments) on Earth keep this hypothesis in consideration.
You mention extremophiles. How old are they?
The oldest direct evidence of life on Earth, which includes extremophiles, dates back at least 3.5 billion years, based on fossilized microorganisms found in ancient rock formations. Some studies suggest that life could have emerged on Earth as early as 4.1 billion years ago, shortly after the planet formed about 4.5 billion years ago.
How could the extremophiles survive the asteroid bombardment 4.1 billion years ago?
The extremophiles could have found refuge deep beneath the Earth’s surface. Some extremophiles are capable of living inside rocks and could have survived by residing in rocks below the impact zones. Hydrothermal vents on the ocean floor, which are rich in chemical nutrients and energy sources necessary for life, could have provided safe havens for extremophiles.
The resilience of microbial life and its ability to recover quickly from catastrophic events is another factor. Microbes can reproduce and adapt rapidly, potentially allowing life to bounce back quickly after the impacts lessened. Additionally, the impacts themselves could have created new habitats (like impact craters filled with water) that could be colonized by extremophiles.