[LINK] "'Rotisserie' Planets Could Host Alien Life — If Wet Enough"

[rfmcdonald]

Space.com's Charles Q. Choi notes a new study suggesting that exoplanets with extreme axial tilts, like that of Uranus in our solar system, could be quite habitable so long as they would have oceans.

"The expectation was that such a planet would not be habitable — it would basically boil, and freeze, which would be really tough for life," lead author of the exoplanet study David Ferreira, a climate scientist at the University of Reading in England, said in a statement.

However, Ferreira and his colleagues' new findings challenge those expectations, showing that such extremely tilted planets may remain habitable if covered entirely by oceans. "In the search for habitable exoplanets, we're saying, don't discount high-obliquity ones as unsuitable for life," Ferreira added in a statement.

To see what life might be like on habitable planets with extreme tilts, researchers simulated Earth-size planets covered entirely in water circling their stars at the same distance as Earth orbits the sun. The 3D models simulated circulation among the atmosphere, ocean and sea ice on "aquaplanets" with oceans 1.8 miles (3 kilometers) deep and "swamp" planets with relatively shallow oceans that were 33 feet (10 meters), 165 feet (50 m) or 655 feet (200 m) deep.

[. . .]

The investigators simulated planets at three obliquities. The first was 23.5 degrees, like Earth's. The next was 54 degrees, the point at which the poles receive more annual sunlight on average than the equator. The last was 90 degrees, the point at which a planet is essentially lying on its side — the poles would each point at the star for a quarter of the year, and then away for another quarter, alternating between extremes of light and darkness.

Ferreira and his colleagues found that a global ocean would absorb enough solar energy from the star and release it back into the atmosphere for such a world to maintain a rather mild, springlike climate year round.