Why we need a new way of thinking about life on Earth
By 2050, we may be living on planets that have been habitable for tens of millions of years, scientists are finding, even as the odds of life evolving on other worlds grow.
For now, the idea of a “New Earth” is a fantasy that has been around for millennia.
But scientists are finally catching on.
In a paper published Monday in the journal Nature, scientists propose a new paradigm for thinking about the cosmos: The notion of a habitable planet is just one of many possible ways to understand the universe.
In this paradigm, we would expect planets to be “habitable” by definition.
The term has been used to describe planets that are warm, moist, and hospitable to life as we know it, and also planets that do not have life.
Earth’s climate is warmer than the planet Venus, for instance, and Earth has been a warm-weather planet for millions of decades.
These are the kind of conditions that are likely to exist on worlds like Earth, said James Martin, a professor of physics and astronomy at the University of California, Berkeley, and a co-author of the paper.
Earth is more hospitable than Mars, and so it’s not hard to see why we would want a planet that is less hospitable.
“If we look at habitable planets as being planets that would have life, that’s a pretty good baseline for our search for life,” Martin said.
He added that even if habitable planets do exist, “that’s a very small sample of habitable planets.”
He added: “We don’t know how much of the habitable space there is in the universe, but it’s pretty clear that there are more habitable planets than we think.”
That doesn’t mean that the search for alien life on other planets will stop anytime soon.
“We’re certainly not going to go back to looking for extraterrestrial life,” said Andrew Siemion, a planetary scientist at the National Oceanic and Atmospheric Administration, who was not involved in the research.
“But this work does bring us closer to understanding the kinds of environments we need to look for life on planets outside of our solar system.”
He said it is likely that if the planets are hospitable, it will take a while before life develops on Earth.
He and Martin said the habitable conditions would be “very different” than what we find on Earth, and that this would not be a problem because “life is an incredibly simple system.”
Martin and Siemion pointed out that the habitable environment on other habitable planets would also be different than the atmosphere on Earth’s surface.
In the future, for example, the planet’s temperature could be “much cooler” than that on Earth because the atmosphere would be colder, so the atmosphere wouldn’t be so much of a barrier to life.
Martin and Martin are working on another study that examines how Earth’s atmosphere changed over time as temperatures and other properties of the planet changed.
Martin said that “the habitable conditions on Earth were quite extreme” and that it is not clear if “habitability” could be defined in the same way as we do now.
The new study was led by Michael E. Smith of the University in Utah, and included contributions from researchers from the United States, Australia, Canada, Germany, China, and India.
This work was supported by the National Science Foundation, the National Institutes of Health, and the American Association for the Advancement of Science.
The work was funded by NASA’s Planetary Science Division, the European Space Agency, the Planetary Science Institute, and by the California Institute of Technology.
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