May 15, 2019

Exo-solar Water Worlds

Timothy Birdnow

Most "sub-Neptune" worlds in other solar systems are probably water worlds, according to new research by NASA.

From Space.com:

Much remains hotly debated about sub-Neptunes, such as how they formed. Their compositions remain unknown, and understanding them could help shed light on these exoplanets' origins. Previous research suggested that sub-Neptunes were either gas dwarf planets with rocky cores surrounded by envelopes rich in hydrogen and helium, or water worlds with major amounts of liquid and frozen water in addition to rock and gas.

To investigate the makeup of sub-Neptunes, scientists ran computer simulations of planetary growth to see what scenarios might best explain the masses and diameters seen to date among exoplanets. Knowing the mass and diameter of a planet can help astronomers estimate its average density, and computer simulations of planetary growth can help reveal whether compositions of gas, rock, ice or water might best explain these densities.

The researchers found that sub-Neptunes are more likely to be water worlds than gas dwarfs. They suggested that each sub-Neptune is at least 25%, and possibly more than 50%,liquid or frozen water by mass. (In contrast, Earth is only 0.02% water by mass.)

"Our study suggests that there are on the order of 1,000 water worlds in just the Kepler confirmed and candidate planets," study lead author Li Zeng, a planetary scientist at Harvard University in Cambridge, Massachusetts, told Space.com. "Statistically speaking, these water worlds may be more abundant than Earth-like rocky planets. Perhaps every typical sunlike star — a star of about one solar mass — has one or more of these water worlds."

With so much water one expects that at least one of them would have developed aquatic life.

Many of these planets would be orbiting flare stars. Most stars are flare stars, and solar flares would wipe out all land life in a close orbit - as in an M class star aka red dwarf. But sea life could well survive. Maybe we are going at this all wrong, looking for alien civilizations on land. Maybe most really smart aliens are aquatic; intelligent squids or starfish or hammerhead sharks. It would be awful hard for them to develop a civilization without fire and not seeing the stars, but then we don't know everything. Maybe they could use chemical reactions or something.

At any rate, this is an interesting point. Water increases the likelihood of life anywhere, at least as we understand it.

Posted by: Timothy Birdnow at 12:28 PM | No Comments | Add Comment
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