It's been a bit of a rollercoaster for scientists studying Proxima b—an Earth-like planet sitting around our solar system's nearest stellar neighbor, Proxima Centauri.
When astronomers confirmed its existence back in 2016, scientists scrambled to figure out if this exoplanet could harbor life. Although it sat in its stars habitable zone, a number of studies soon cast the prospect of possible alien life into doubt.
But now, a NASA-led study has offered an olive branch to Proxima b believers. Scientists used sophisticated 3D simulation techniques to produce a number of scenarios in which life could survive on the exoplanet. Their research was published recently in the journal Astrobiology.
Various obstacles stand in the way of life on Proxima b. Although it sits close enough for liquid water to theoretically persist, scientists actually don't know if it has any. "We don't know whether [the exoplanet] even has an atmosphere, and if it does, whether it has any water. Without those, life as we know it cannot exist," study author Anthony Del Genio from the NASA Goddard Institute for Space Studies told Universe Today.
Even if it held water in the past, there's good reason to think the planet is arid now. Its host star is a red dwarf far cooler and smaller than our own sun, Del Genio said, with a correspondingly close zone of habitability. Because it's a pretty active star, planets inside that golden ring are at risk from powerful flares.
In March 2017 a gigantic flare from Proxima Centauri zapped Proxima b. Scientists think these bright outbursts may have slowly eaten away at the planet's atmosphere and wiped out its water.
But a number of scenarios could have left Proxima b with at least a little water, Del Genio explained. If the planet was very wet when it formed, for example, some of that liquid might still persist. It may also have started out further away from Proxima Centauri and slowly moved closer to the star, providing protection from powerful flares in its early days, he told Universe Today.
The researchers' software simulated several climate scenarios. In one model, the planet had an Earth-like atmosphere and in another it had one like Mars. In one simulation it was tidally locked to its star, and in another it was covered by an enormous ocean.
"For each configuration that we imagine, we run a 3D global climate model that is adapted from the Earth climate model that we use to project 21st century warming," Del Genio explained. "The key feature of our climate for this purpose is that we include a 'dynamic' ocean."
Where other studies have imagined an ocean that stays pretty still, the currents of a dynamic ocean would transfer warm water to cooler areas, he added.
"If Proxima Centauri b has an atmosphere and ocean, the ocean is a moderating influence on its climate—the dayside would be cooler, and the nightside warmer, than previous estimates have suggested," he told Newsweek.
This kind of ocean, the team discovered, could help Proxima b sustain at least some surface water in a wide range of scenarios. Even the permanently dark side of a tidally-locked planet could remain habitable with a dynamic ocean, they found. Salty waters, for example, could keep water liquid even below its normal freezing point.
But of course, the research doesn't tell us whether or not there actually is an atmosphere or any water on Proxima b. "There are reasons why it might not, but until we have data, we don't know," Del Genio said. "Our study is designed to help in the interpretation of such data."
Del Genio told Newsweek he now hopes to investigate the possible effects of ocean currents on the habitability of other exoplanets.
Scientists hope upcoming instruments, such as NASA's planet-hunting James Webb Space Telescope, will reveal more details about exoplanets like Proxima b. The Kepler space observatory, launched back in 2009, has discovered thousands of planets over its lifetime.
This article has been updated with further comment from Anthony Del Genio.
Uncommon Knowledge
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Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
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