As the tilt axis and the depth of the ocean determine the suitability of exoplanets for life?





About 2000 planets outside of ourSolar system was discovered to the present moment. Whether any of these exoplanets to be inhabited, depends on a number of criteria. Among them, according to scientists, there is such criterion as the axial tilt of the planet relative to the orbit around the star. The greater the slope, the less chance for life. Anyway, thought astrobiologists.

Scientists at mit have discovered that even a planet with a severe slope, with nearly horizontal axis, could potentially support life, assuming that the entire planet is covered by ocean. Even a shallow ocean, about 50 meters depth will be able to maintain on the planet a comfortable temperature of 15 degrees Celsius all year round.

David Ferreira, a former researcher at mit, says at first glance it may seem that the planet with such an extremely tilted axis will be uninhabitable if the planet is practically lying on its side, the North pole will be covered six months a year, and then six months of darkness.

"We thought that this planet may not be habitable: it would either boil or freeze, for life is unacceptable, says Ferreira. But we also found that the ocean stores heat and returns it in the winter, so the climate can be quite mild even in the heart of the cold polar night. Thus, when we are looking for habitable exoplanets, we should not underestimate the planet with a seriously tilted axis".

The results of the research were published in the journal Icarus. Together with colleagues Ferreira used a model developed at MIT that simulates a "aquaplanet" tilted axis, the size of the Earth, with the same distance to the Sun, but fully covered with water. A three-dimensional model is constructed to simulate the circulation of the atmosphere, ocean, sea ice, wind and heat. For comparison, the scientists built several models with different depths of the ocean: 200, 50 and 10 metres, and with different slopes: 23 (as of the Earth), 54 and 90 degrees.

In the case of planets with 90-degree tilt axis, the scientists found that the oceans even to a depth of 50 metres will absorb enough solar energy during the polar summer and release it back into the atmosphere in winter, thus maintaining a relatively mild climate. Year-round on the planet will be dominated by spring temperatures.

"We expected that if you put an ocean on the planet, it will be more suitable for life, but not to this extent. Indeed, it is surprising that the temperature at the poles remains favorable for life."

The team came to the conclusion that life can thrive in a water aquaplanet tilted, but only to a certain point. The depths of the ocean 10 meters is no longer sufficient to maintain a mild climate. On the contrary, the earth will experience the opposite effect: as soon as the ice forms, it quickly spread to the dark side of the planet. And even when this side turns to the sun, it will be too late: massive ice strata will reflect the sun's rays, allowing the ice to spread further, until it will engulf the entire planet.

"Some people think that on a planet with a tilted axis is the ice at the equator and at the poles would be warm. But we came to the conclusion that there are no intermediate States. If the planet is not enough ocean, it will turn into a snowball. Of course, it inhabited not exactly call".

Source: hi-news.ru

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