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What if we dropped the ‘earthly’ from the ‘alien’? Scientists recently explored the intriguing possibility that alien life might not need a planet to sustain itself.
At first glance, planets seem like ideal locations to find life. After all, the only known place where life exists is the Earth’s surface. And Earth is quite nice. Our planet has a deep gravity well that holds everything in place and is thick realm that keeps the surface temperature within the correct range to maintain liquid water. We have an abundance of elements such as carbon and oxygen to form the building blocks of biological organisms. And there’s a lot of sunlight shining on us, providing an essentially limitless source of free energy.
We organize our activities based on this basic setup searches for life elsewhere in the universe. Sure, there may be exotic environments or crazy chemistry involved, but we still assume that life exists on planets because planets are naturally so suited to life as we know it.
In a recent pre-paper accepted for publication in the journal Astrobiologyresearchers are challenging this basic assumption by asking whether it is possible to engineer an environment in which life can thrive without a planet.
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This idea is not as crazy as it sounds. In fact, we already have an example of beings living in space without a planet: the astronauts on board the International Space Station. These astronauts require enormous amounts of Earth resources constantly transported to them, but humans are incredibly complex creatures.
Perhaps simpler organisms could make it on their own. At least one known organism, the little tardigrades, can survive in the vacuum of space.
Every community of organisms in space must face different challenges. First, it must maintain an internal pressure against the vacuum of space. So a colony stationed in space would have to form a membrane or shell. Fortunately, this isn’t too much of a problem; it is the same pressure difference as that between the water surface and a depth of about 10 meters. Many organisms, both microscopic and macroscopic, can easily handle these differences.
The next challenge is maintaining 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 extant organisms, such as the Saharan silver ant (Cataglyphis bombycina), which can regulate their internal temperatures by varying which wavelengths of light they absorb and which they reflect – essentially creating a greenhouse effect without an atmosphere. The outer membrane of a free-floating colony of organisms should therefore have the same selective ability.
Next, they would have to overcome the loss of lightweight elements. Planets retain their elements through the sheer force of gravitybut an organic colony would have difficulty with this. Even optimistically, a colony would lose lightweight elements over tens of thousands of years, and so would have to find ways to replenish itself.
Finally, the biological colony should be placed within the habitable zone of its star, to access as much sunlight as possible. As for other resources, such as carbon or oxygen, the colony would have to start with a steady supply, like an asteroid, and then move to a closed recycling system between the different components to sustain itself in the long term.
Taken together, the researchers paint the portrait of an organism, or colony of organisms, floating free in space. This structure could be up to 100 meters in diameter and would be encased in a thin, hard, transparent shell. This shell would stabilize the inland water at the correct 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 efforts in space. While we currently build habitats with metal and supply our stations with air, food and water transported from Earth, future habitats could use bioengineered materials to create self-sustaining ecosystems.
Originally posted on Space.com.