Planets Bursting With Alien Life Might Exist Beyond the Solar System, Scientists Claim: 'We Need to Start Looking'

Scientists have identified more than 4,000 confirmed planets outside of our solar system. Now research suggests that some of these exoplanets may actually be more hospitable to life than Earth itself.

Because these planets are so far away—hundreds, even thousands of light-years away—scientists mainly learn about them through remote observations, using telescopes and other equipment. But to understand more about their characteristics and whether they could host life, researchers have developed sophisticated planetary models.

Existing models tend to overlook ocean dynamics, or the role that oceans play in transporting heat around a planet and regulating its climate. On Earth, these dynamics are crucial in determining the "productivity and distribution of life today and throughout the planet's history," according to research presented by University of Chicago geochemist Stephanie Olson at the recent Goldschmidt Geochemistry Congress in Barcelona.

"The search for life beyond our solar system has focused on planets with the potential for oceans at their surface because life as we know it requires liquid water," Olson told Newsweek. "However, oceans are dynamic habitats, and life has additional requirements for its environment. Of particular importance on Earth are nutrients like phosphate, which is a key component of DNA. Phosphate and other nutrients tend to gravitationally accumulate at depth in Earth's ocean because dead cells sink through the water column."

"For this reason, the distribution and activity of life in our ocean is controlled by ocean circulation that transport nutrient-rich waters from depth to the nutrient-poor surface," in a process known as upwelling, she said. "This will be true for photosynthetic biospheres on other planets as well. We know that atmospheric circulation differs dramatically among habitable planets—but the details of ocean circulation on other planets and its implications for nutrient supply have never been explored. Our study addresses this critical issue."

This artist's concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets' diameters, masses and distances from the host star, as of February 2018. Three of the seven exoplanets are in the "habitable zone," where liquid water is possible. NASA/JPL-Caltech

Olson and her colleagues explored ocean dynamics among a variety of different exoplanets using a system known as ROCKE-3D to determine which types have the most ocean upwelling and may therefore host the most active biospheres. The software—developed by NASA—enables scientists to simulate the climates and ocean environments of exoplanets.

Olson systematically varied key planetary properties in the model, including surface pressure, rotation rate, radius, ocean salinity and the amount of stellar energy the planet receives, then quantified how ocean circulation patterns changed in response.

The modeling revealed which kinds of exoplanets are more likely to support the right conditions for "globally abundant and active life."

"We found that ocean circulation patterns will differ among habitable planets—and these differences may be biologically important," Olson said. "High surface pressures and slow rotation rates compared to Earth enhance ocean upwelling, and thus increase the potential for nutrient replenishment. Coastal upwelling is particularly important for nutrient recycling, and so planets that lack continents might not be good places to live."

"This is a surprising conclusion," she said. "Ocean circulation patterns may allow life that is more abundant or more active than life on Earth. This means that some planets might host life that will be easier to detect than life on an Earth-twin."

The results could have significant implications in the search for extraterrestrial life, she added. "In the search for life beyond our solar system, the most promising planets might not be Earth twins."

Olsen admits, though, that her hypothesis can only be tested with next-generation telescopes, which are not yet operational.

"There will always be limitations to our technology, so life is almost certainly more common than 'detectable' life," she said. "This means that in our search for life in the universe, we should target the subset of habitable planets that will be most favorable to large, globally active biospheres because those are the planets where life will be easiest to detect—and where non-detections will be most meaningful."

"Ideally this work this will inform telescope design to ensure that future missions—such as the proposed LUVOIR or HabEx telescope concepts—have the right capabilities; now we know what to look for, so we need to start looking."

Douglas Gobeille, a physics professor at the University of Rhode Island, praised Olson's work.

"Liquid water is the litmus test for the habitability of life as we currently know it," Gobeille, who was not involved in the research, told Newsweek. "Dr. Olson's research proposes a sharper focus on which of these worlds hold the greatest potential for the birth, evolution, and maintenance of life. This work widens the field of worlds on which life might arise by suggesting that twins to Earth can produce life, but others might do so more readily."

"It will be exciting to see how this work influences the myriad candidates for life, including on super-Earths," he said. "These planets, with masses 2-10 times that of Earth and perhaps up to 25 percent larger in radius, with their increased gravity, may have surfaces more like great island chains compared to Earth's numerous above sea-level land masses. While there are no super-Earths in the solar system, this research will further influence the search for life on potential worlds closer to Earth with liquid oceans, such as Jupiter's moons Europa and Saturn's moons Enceladus and Titan."

Gobeille notes that this research will likely be of great interest to upcoming spacecraft missions to Europa, including the European Space Agency's JUICE (Jupiter Icy moons Explorer) and NASA's Europa Clipper mission.

Terry Oswalt, a professor of physics at Florida's Embry-Riddle Aeronautical University, said that Olson and her team make a "very interesting point" that Earth's environment may not be optimal for life.

"For one thing, human activities have been affecting our climate, and not in a good way," Oswalt told Newsweek. "In addition, Earth has natural cycles like ice ages, abrupt events like huge volcanic explosions, gradual continental drift, etc. that make our environment change. Olson's group investigated how oceans affect the habitability of Earth-like planets. The circulation of ocean water, the heat it can retain or emit, the chemicals it can dissolve or release into the environment all contribute to habitability. Being warm and having liquid water are only two of many important factors in the possible emergence of life."

"Olson's models show that oceans have a strong influence on which planets inside the habitable zone of their parent star might or might not be habitable," he said. "The results will help astronomers to focus their studies first on the most likely "Earth-like" exoplanets. It may also help current climatologists understand better how to deal with our global warming problem."

Oswalt said the fact that a dozen or so bodies in the solar system—like Europa—seem to have icy crusts shielding deep warm oceans suggests that life may more likely be found on planets or moons which seem uninhabitable at first glance.

"So far, we don't have the technology to explore the effects of oceans on other planets in detail, so the Earth and its oceans provide the best way to test such models," he said. "It's exciting to see astronomy, biology, chemistry, geology, oceanography and physics converging on such profound questions as where we should look for life outside—and elsewhere inside—the solar system."

NASA's James Webb Space Telescope, the successor to the Hubble Space Telescope, is expected to launch in 2021 and ultimately reveal characteristics of exoplanets in unprecedented detail, enabling astronomers to determine how many have oceans like Earth.