As far as researchers know, this requires a planet to have liquid water. As researchers learn more and discover new environments in which life can sustain itself, the requirements for life on other planets may be redefined.
Different types of planets may drive processes that help or hinder habitability in different ways. For example, planets orbiting low-mass stars in the habitable zone may be tidally locked, with only one hemisphere facing the star at all times. Some planets may be limited to only periodic or local habitable regions on the surface if, e.
In order to understand the full range of planetary environments that could support life and generate detectable biosignatures, we require more detailed and complete models of diverse planetary conditions. In particular, understanding the processes that can maintain or lead to the loss of habitability on a planet requires the use of multiple coupled models that can examine these processes in detail, especially at the boundaries where these processes intersect each other.
By studying ways that biospheres interact with planetary environments, SEEC researchers are pioneering methods to detect life on other worlds. There may be no shortage of energy sources for life to live off. Scientists have argued that habitable worlds need stars that can live at least several billion years, long enough for life to evolve, as was the case on Earth. Some stars only live a few million years before dying. Still, "life might originate very fast, so age is not that important," astrobiologist Jim Kasting at Pennsylvania State University told OurAmazingPlanet.
For instance, the Earth is about 4. The oldest known organism first appeared on Earth about 3. However, more complex forms of life did take longer to evolve — the first multicellular animals did not appear on Earth until about million years ago.
Because our sun is so long-lived, comparatively, higher orders of life, including humans, had time to evolve. Other researchers have suggested that plate tectonics is vital for a world to host life — that is, a planet whose shell is broken up into plates that constantly move around.
For instance, carbon dioxide helps trap heat from the sun to keep Earth warm. This gas normally gets bound up in rocks over time, meaning the planet would eventually freeze. Plate tectonics helps ensure this rock gets dragged downward, where it melts, and this molten rock eventually releases this carbon dioxide gas back into the atmosphere through volcanoes. Seager agreed, saying that "volcanism might very well provide enough fresh supplies of whatever life might need.
Other factors researchers have trotted out for why life succeeded on Earth include how little variation there is in our sun's radiation compared with more volatile stars, or how our planet has a magnetic field that protects us from any storms of charged particles from the sun. Violent bursts of radiation could have scoured life from Earth in its early, fragile stages.
Still, "people are constantly rethinking each of these things and how important they are," Seager said. We want to learn about what gray areas might exist for possible life. Earth remains the only known planet to host life, due to a unique combination of factors.
However, continued monitoring of alien worlds might one day change that, by finding other planets that share these attributes or by discovering other ways that life has found to blossom in the universe. Live Science. Charles Q.
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