In the last few decades, scientists, especially astrobiologists, have come to the realization that water is necessary to support life outside of our solar system. But, how much water exactly? Some of whom are searching for any type of carbon-based life outside of our world have concluded that it is not only water that is needed to harbor a home for E.T., but oceans.
David Stevens, professor of applied mathematics at the University of East Anglia in England, stated, “The number of planets being discovered outside our solar system is rapidly increasing.” Since 1971, at the inception of the Search for Extraterrestrial Intelligence (SETI) program, NASA has mainly focused on radio signal detection to determine where to look for intelligence. Beginning in 2009, the Kepler Space Program was launched by the observatory with the same name, the Kepler Space Observatory. This project was aimed at finding extrasolar bodies within the Milky Way Galaxy that could have the potential to harbor life.
The telescope and its operators use Doppler spectroscopy and transit timing to calculate how large an exoplanet is, how far away from its host star, and its orbital circumference and velocity. All of this sounds exciting and promising; however, the program has overlooked one underlying factor, the largest piece of the puzzle in the search for finding our cosmic brothers and sisters – water and lots of it. Recently, scientists have found a way to tell whether or not a planet can support carbon-based life based on its water-bearing qualities.
In the solar system, Earth lies within the habitable zone, or “Goldilocks” zone due to its location from the Sun being just right to support a temperature for liquid water to exist. Though, if we look to the next planet, Mars, it is also in the habitable zone, albeit, nearing the outside edge. Why is there no life on the red planet? Well, Stevens and his team state that the reason why is because there are no oceans.
Stevens explained that former habitability models have neglected to encompass oceans as a primary factor when searching for an Earth-like planet. The aforementioned space exploration programs only calculated locations of planets that had similar sizes and orbits in regards to Earth and not the geographical and meteorological characteristics of its surface and atmosphere. On Earth, water in its liquid form is only physically possible between 32 degrees Fahrenheit and 212 degrees Fahrenheit at normal pressure boundaries. On a cosmic scale that is a fairly small margin.
Scientists have now taken the search criteria to the next level. The most important factor in locating oceans on the surface of an alien world is that they regulate temperatures across the planet. On Earth, the large bodies of water transport heat to and from different parts of globe and distribute it rather evenly. On Mars, however, temperatures can vary up to 180 degrees Fahrenheit on any given day. There is no medium through which heat can be transported and dispersed. Therefore, Stevens’ team has been creating computer models to simulate how a planet’s rotation velocity affects the transportation of heat when and if oceans are present.
Stevens explained that large bodies of water are necessary because, “they cause the surface temperature to respond very slowly to seasonal changes in solar heating.” If temperature swings become too rapid then the surface temperature will become intolerable. He also noted that overly-simplified models including an “aquaplanet” like Titan, one of Jupiter’s moons, fail to consider the impact land barriers would have on the distribution of heat around the surface of a planet.
Stevens’ project is shedding much needed light on the way habitable planets are examined. His models have the potential to create a fresh understand about the necessary qualifications a planet needs in order to harbor life. He and his team have proved that there is more to the “Goldilocks” zone than was previously thought. It is no longer just orbital velocity and distance from a host star; it is a multitude of fragile atmospheric, geological, and astronomical variables that make the equation for the possibility of life to exist. Even though nearly 1,800 Earth-like planets have been located in the Milky Way galaxy, it is almost certain that much more scrutiny will be needed to determine which, if any, have oceans that can harbor our cosmic relatives.
By: Alex Lemieux