Scientists have found that “Goldilocks Zones” around stars, those areas of habitability that are derived by the distance of a planet from its parent star where it has the capacity to sustain living organisms as we understand it, is not just as simple as orbital distance. A new study suggests that there is another key factor that influences whether or not a planet can sustain life, or at least the conditions conducive to sustaining life.
Phys.org reported on August 19 that there exists a separate “Goldilocks” factor that scientists believe is essential for a planet, or exoplanet, to sustain life — and just being safely within the general parameters of the habitable zone is not enough. That separate factor, according to Yale professor of geology and geophysics Jun Korenaga, is that the internal temperature of the exoplanet has to be just right.
This, in effect, deals a limiting factor into the cosmic game of life that restricts the overall number of habitable exoplanets, or at least those that would be suitable to sustain life as it is currently understood to exist.
Korenaga, who was lead author on the study, notes that mantle convection is “indifferent” to the internal temperature of a planet. Korenaga sets up a general theoretical framework in the study, which was published in Science Advances, wherein the level of self-regulation necessary for mantle convection is explained. The study also suggests that such self-regulation is an unlikely attribute for rocky, or Earth-like, planets.
“The lack of the self-regulating mechanism has enormous implications for planetary habitability. Studies on planetary formation suggest that planets like Earth form by multiple giant impacts, and the outcome of this highly random process is known to be very diverse.”
In short, even though it is estimated, as the New York Times noted in 2013, that there could be as many as 40 billion habitable planets orbiting red dwarfs and Sol-like stars in the Milky Way galaxy alone, a great majority of them may not have the “Goldilocks” factor of maintaining a self-regulating internal temperature. The habitable planet calculation was made through the work of University of California graduate student Erik Petigura, who pored over Kepler telescope data for three years to arrive at his estimation.
The size and diversity of the exoplanets does not matter, just as long as the self-regulating mantle convection exists. The study also explains that Earth’s oceans and continents would not exist if the internal temperature of Earth had not been in a certain range. By extension, this would include the beginning of Earth’s history, where the internal temperature would have not be too hot or too cold.
Besides professorial duties at Yale, Korenaga also works on NASA’s “Alternate Earths” team as an co-investigator. The team itself, as explained by Phys.org, is “organized around the principle of understanding how the Earth has maintained a persistent biosphere through most of its history, how the biosphere manifests in ‘biosignatures’ on a planetary scale, and how reconstructing this history can inform the search for life within and beyond the solar system.”
Jun Korenaga’s new “Goldilocks” parameter is a limiting factor in the search for alien life, one that adds to the many limitations already in place with regard to finding life elsewhere in the universe. Although it has been found that the elements for the creation of living organisms is readily abundant throughout the universe, the restrictive boundaries, within which life emerges and evolves, seems to be governed by a multitude of factors.
So how do astronomers find exoplanets that meet this second “Goldilocks” criterium? Now, that is a problem that will likely be solved backwards, whereas alien life might have to be discovered first, with the exoplanet’s geologic make-up and history verified later. In this regard, intelligent aliens would be a big help.
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