Scientists have recently explored the intriguing possibility that extraterrestrial life may not need a planet to sustain itself.
At first glance, planets seem like ideal places to find life. After all, the only known place where life is known to exist is the Earth’s surface. Our planet has a deep gravitational well that holds everything in place and a thick atmosphere that keeps surface temperatures just right to keep water liquid.
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 us with an unlimited supply of free energy.
Starting from this basic configuration we organize our searches for life elsewhere in the universe. Of course, there could be exotic environments or crazy chemistries involved, but we still assume that life exists on planets because planets are so naturally suited for life as we know it.
In a prepaper recently accepted for publication in the journal Astrobiology, the researchers question this basic assumption, asking whether it is possible to build an environment that would allow life to develop without a planet.
This idea is not as crazy as it sounds. In fact, we already have an example of creatures living in space without a planet: the astronauts aboard the International Space Station. These astronauts need huge amounts of resources from Earth to be constantly transported to them, but humans are incredibly complex creatures.
Important implications for future endeavors in space
Perhaps simpler organisms could fend for themselves. At least one known organism, the tiny water-dwelling tardigrades, is capable of surviving in the vacuum of space.
Any community of organisms in space must face several challenges. First, it must maintain an internal pressure against the vacuum of space. Thus, a space colony should form a membrane or shell. Fortunately, this is not such a big problem; it is the same pressure difference as that between the surface of the water and a depth of about 10 meters. Many organisms, both microscopic and macroscopic, can easily cope with these differences.
The next challenge is maintaining a high enough temperature for liquid water. Earth accomplishes this through the greenhouse effect of the atmosphere, which will not be an option for a smaller biological space colony. The authors cite existing organisms, such as the Saharan silver ant (Cataglyphis bombycina), which can regulate their internal temperature by varying the wavelengths of light they absorb and reflect—essentially creating a greenhouse effect without an atmosphere, they write LiveScience.
Then they should overcome the loss of light elements. Planets maintain their elements by gravitational force, but an organic colony would have trouble with this. Even optimistically, a colony would lose light elements over tens of thousands of years, so it would have to find ways to replenish itself.
An abundance of elements
Finally, the biological colony should be positioned in the habitable zone of its star to have access to as much sunlight as possible.
As for other resources, 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-loop recycling system between its various components to maintain itself in the long term.
Putting it all together, researchers describe an organism or colony of organisms floating freely in space. This structure could be up to 100 meters in diameter and would be contained by a thin, hard and transparent shell. This shell would stabilize the water inside at the right pressure and temperature and allow it to maintain a greenhouse effect.
Although 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 out of metal and power our stations with air, food and water transported from Earth, future habitats could use bioengineered materials to create self-sustaining ecosystems.
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Source: www.descopera.ro
