Astronomers Want to Find the Habitable Planet Where Alien First Life
- SoundCloud
VIVA – Once life gains even the tiniest foothold on a planet, it may have the power to transform that world, forcing us to broaden our definition of “habitable” new research suggests. Currently, we don’t really know where life might arise. We have only one example of a life-hosting planet, Earth, which started to get interesting perhaps only a few hundred million years after it formed.
Life on Earth required a certain set of elements to perform its complex chain of energy production it needs liquid water as a solution, and it can exist only in a relatively narrow range of atmospheric temperatures and pressures.
In the search for life beyond Earth, astronomers generally focus on areas called habitable zones, orbital bands around stars where liquid water could potentially exist on a planet's surface.
If a planet is closer to the star, water will evaporate from its heat. But if it's farther from the star, the water will freeze into ice. Neither of these conditions is good for life as we know it. But the habitable zone is only a rough guide, not a guarantee. Mars and Venus are within the Sun's habitable zone, but those planets are uninhabited.
Alien.
- Tech Explorist
Earth would be completely different if it weren't for life. The classic example is the abundant quantities of oxygen in our planet's atmosphere.
Oxygen is a very common element throughout the cosmos, and Earth was born with a lot of it. But most of that oxygen is bound up in the form of silicon dioxide rocks. Gaseous oxygen can't survive in the atmosphere long, because ultraviolet radiation from the sun breaks it apart.
But the process of photosynthesis releases oxygen gas as a byproduct. In fact, early life produced so much oxygen that it almost poisoned itself in an incident known as the Great Oxidation Event. It took the evolution of oxygen-breathing creatures to put the ecosystem back in balance.
This line of thought can be extended to many other properties of the atmosphere. Living things also emit large amounts of methane, a greenhouse gas that helps keep our planet warm.
Extensive forest canopies alter the amount of sunlight reflected off the surface, also affecting the temperature of our world. Even the production of various gaseous byproducts from creatures large and small can change the air pressure of planet Earth's atmosphere.
The earliest possible signs of life on our world in the fossil record suggest that life may have emerged when parts of our planet were still liquid. It must have been a very hostile place. But billions of years later, that's pretty good.
The authors of the new paper envision a world at the edge of the habitable zone, either almost too cold or almost too hot.
But if alien life managed to start there, it would have the opportunity to improve the makeup of the planet, perhaps by raising or lowering atmospheric pressure or temperature, or by creating recesses underground where life could thrive. Therefore, we must rethink the traditional definition of the habitable zone.
