A
nearby exoplanet orbiting within the habitable zone of a star just 4.2
light-years from Earth may be home to a vast ocean, boosting its chances of
supporting life. Since its discovery, questions about the conditions at the
surface of Proxima b have been swirling; the planet’s mass is just about 1.3
times that of Earth’s, and the red dwarf star it circles is similar in age to
our sun.

Studies
over the last few years, however, have both bolstered hopes of its habitability
and shot them down. Now, a new study has once again raised the possibility that
Proxima b could support life, suggesting that under the right conditions, the
exoplanet could sustain liquid water.
“The
major message from our simulations is that there’s a decent chance that the
planet would be habitable,” Anthony Del Genio, a planetary scientist at the
NASA Goddard Institute for Space Studies, told LiveScience.

Since
its discovery, questions about the conditions at the surface of Proxima b have
been swirling; the planet’s mass is just about 1.3 times that of Earth’s,
and the red dwarf star it circles is similar in age to our sun. Artist's
impression
In
the study published this month in the journal Astrobiology, the researchers ran
what are said to be the first climate simulations of Proxima b with a dynamic
ocean. The planet is thought to be tidally locked with its star, Proxima
Centauri, meaning it would have a permanent ‘dayside’ and ‘nightside.’
While
any water on the side left in the dark would be frozen, that’s not necessarily
the case for the other side.
“Climate
models with static oceans suggest that Proxima b could harbor a small dayside
surface ocean despite its weak instellation,” the researchers explain in the
new study. “With a dynamic (moving) ocean considered for the first time, the
extent of this liquid water becomes much more significant, in some cases even
dipping into parts of the nightside. The simulations showed that ‘with a
dynamic ocean, a hypothetical ocean-covered Proxima Centauri b with an
atmosphere similar to modern Earth’s can have a habitable climate with a broad
region of open ocean, extending to the nightside at low latitudes.”

Proxima
b orbits the red dwarf Proxima Centauri, which is part of a triple system
including the binary pair Alpha
Centauri A and B. An artist's impression is picturedÂ
The
researchers modelled for different salinity levels and atmospheric greenhouse
gas concentrations as well, each of which could play into the size of the
liquid regions. In more than a dozen simulations, the team found the exoplanet
almost always had some sort of liquid ocean. But, don’t get excited to take a
dip just yet.
“We
find that an ocean-covered Proxima b could have a much broader area of surface
liquid water but at much colder temperatures than previously suggested, due to
ocean heat transport and/or depression of the freezing point by salinity,” the
researchers wrote.
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