Did you know that the habitable zone of a solar system is the range of distance from the sun that is “neither too hot nor too cold, but just right” for life?
It is also known as the Goldilocks Zone!
The Earth has experienced an enormous amount of temperature changes since it formed more than 4 billion years ago. Currently, the average temperature of our planet is about 0.9ºC. This is an average temperature across all regions of the Earth throughout the year, and is consistent with the average temperature in many parts of Ontario!
The coldest regions on Earth, the north and south poles, can experience temperatures as low as -89oC (Vostok Station, Antarctica). On the other hand, our warm equatorial regions can register temperatures of up to 54oC (Death Valley, USA and Mitribah, Kuwait).
Therefore, the Earth supports life over (what we perceive as) a wide range of temperatures.
But what does this tell us about the possibility of life forming in our solar system and in other solar systems that are now being discovered?
The Goldilocks area
For many decades, astrobiologists have been studying and developing models of how life can form on other planets. They examine a wide variety of factors, including temperature, pressure, humidity, chemical composition, stellar radiation (e.g., the effects of ultraviolet light), and more.
One of the ideas that has been developed well, at least for human life, is the idea of the Goldilocks Zone.
Petigura/UC Berkeley, Howard/UH-Manoa, Marcy/UC Berkeley
The Goldilocks Zone (or habitable zone), named after the phrase “not too hot, not too cold, but just right,” represents an area around a star that has the right conditions to allow the presence of liquid water (between 0 °C and 100 °C).
In our solar system, the habitable zone exists between Venus (on the warm side) and Mars (on the cold side). However, other conditions on the planet itself can affect its ability to host liquid water. For example, salinity (amount of salt) and surface pressure can greatly affect whether water is in a liquid, gaseous, or frozen state.
Venus should have liquid water, but because of the runaway greenhouse effect, the temperature and pressure are too high for liquid water to exist (there is significant evidence that Venus had oceans in the past, but they have long since evaporated).
Mars, on the other hand, should also be able to contain liquid water. However, its small size, together with its low atmospheric pressure, ensure that liquid water can only exist in a few well-defined areas (one of them, the Hellas basin, should be able to contain water, but so far it has not been proven. detected nothing).
However, there is significant evidence of frozen water on Mars and an ocean in the distant past, the remains of which may be frozen beneath the surface.
Astronomers use the habitable zone principle to evaluate whether a new exoplanetary system (a star system containing planets) may have one or more planets that possibly host liquid water. Currently, of the thousands of exoplanets discovered so far, there are only a few good candidates for planets within habitable zones, favorable for the formation of life.
So the next time you are outside, especially as a Canadian, and complain that it is too hot or too cold outside, remember that things could be much worse and that we are lucky to live on a planet that is “perfect.”
Note: Just because our planet can continue to support liquid water within a range of temperatures does not mean it can continue to support the United States within a range of temperatures. Parks and protected areas play a crucial role in mitigating climate change and ensuring that the Earth’s temperature remains “just right” for its diverse range of life.
Learn more about how climate change affects Ontario’s natural resources (e.g. plants, wildlife, forests, wetlands, parks) here.