What if we took the “terrestrial” out of “extraterrestrial”? Scientists recently explored the intriguing possibility that alien life may not need a planet to support itself.
At first glance, planets seem like ideal places to find life. After all, the only place where life is known to exist is the Earth’s surface. AND earth it is very beautiful. Our planet has a deep gravitational well that holds everything in place and a thick one atmosphere which keeps surface temperatures within the right limits to hold liquid water. We have an abundance of elements like carbon and oxygen to form the building blocks of biological organisms. And we have plenty of sunlight shining down on us, providing an essentially limitless source of free energy.
It is from this basic configuration that we organize ours looking for life elsewhere in the universe. Sure, there may be exotic environments or crazy chemistry, but we still assume that life exists on planets because planets are so naturally suitable for life as we know it.
In a recent preview accepted for publication in journal Astrobiologyresearchers challenge this basic assumption by asking whether it is possible to build an environment that allows life to flourish without a planet.
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This idea is not as crazy as it seems. In fact, we already have an example of creatures living in space without a planet: astronauts on board International Space Station. These astronauts require tremendous amounts of Earth-based resources to be constantly transferred to them, but humans are incredibly complex creatures.
Perhaps simpler organisms can manage it themselves. At least one known organism, the tiny water-dwelling tardigrades, is able to survive in the vacuum of space.
Any community of organisms in space must deal with certain challenges. First, it must maintain an internal pressure against the vacuum of space. So a space-based colony must form a membrane or shell. Thankfully, this isn’t a huge deal; it is the same pressure difference as that between the surface of the water and a depth of about 30 feet (10 meters). Many organisms, both microscopic and macroscopic, can handle these differences with ease.
The next challenge is to maintain a temperature warm enough for liquid water. Earth achieves this through the greenhouse effect of the atmosphere, which will not be an option for a smaller biological space colony. The authors point to existing organisms, such as the Saharan silver ant (Cataglyphis bombycina), that can regulate their internal temperatures by changing which wavelengths of light they absorb and which they reflect—essentially, creating a greenhouse effect without an atmosphere. So the outer membrane of a colony of free-floating organisms would have to achieve the same selective abilities.
Then, they will have to overcome the loss of light elements. The planets maintain their elements through the great force of gravitybut an organic colony would struggle with that. Even optimistically, a colony would lose light elements over the course of tens of thousands of years, so it would have to find ways to replenish itself.
Finally, the biological colony would need to be positioned within the habitable zone of its star, to access as much sunlight as possible. As for other sources, such as carbon or oxygen, the colony would have to start with a stable supply, such as an asteroid, and then switch to a closed recycling system between its various components to sustain itself for a long term.
Putting it all together, researchers paint the picture of an organism, or colony of organisms, floating freely in space. This structure could be up to 330 feet (100 m) across and would be contained by a thin, hard, transparent shell. This shell would stabilize its internal water at the right pressure and temperature and allow it to maintain a greenhouse effect.
While such organisms may or may not exist in the universe, the research has important implications for future human endeavors in space. While we currently build habitats with metal and supply our stations with air, food and water transported from Earth, future habitats may use bioengineered materials to create self-sustaining ecosystems.
Originally posted on Space.com.