Experts suggest that scientists should take a more conservative approach in their search for habitable planets, which means looking for planets that have liquid water and solid or liquid surfaces rather than gas giants like Saturn and Jupiter.
The habitable zone of a solar system is defined as the region where liquid water could exist. Experts suggest that defining this habitable zone is key to the search for life sustaining planets in part because the idea of a habitable zone is used in designing the space-based telescopes that scientists would use to find planets where metabolism, and potentially life might exist, a press release reveals.
"It's one of the biggest and oldest questions that science has tried to investigate: is there life off the earth?" James Kasting, professor at Penn State said. "NASA is pursuing the search for life elsewhere in the Solar System, but some of us think that looking for life on planets around other stars may actually be the best way to answer this question."
Ravi Kopparapu, a post-doctoral researcher working with Kasting revealed that the chances of finding Earth-like planets in the habitable zones of stars known as M-dwarfs are 0.4 to 0.5. In order to find four such planets, scientists would need to survey the habitable zones of at least 10 cool stars.
Eric Petigura and colleagues at the Kepler Science Conference in early November provided another such estimate calculating the chances to be 0.22 around stars similar to the Sun. However, other scientists speculated that this reading may not be correct because Petigura used an overly optimistic estimate for the width of the habitable zone for this research.
The ability of a planet to sustain liquid water is one of the biggest criteria while looking for life-sustaining planets. Many scientists have argued that subsurface water would be enough to sustain life. However, testing this hypothesis remotely is virtually impossible, so the focus for astronomers remains on surface water.
"All life that we know of is carbon-based and depends on the presence of liquid water during at least part of its life cycle," Kasting noted in the research paper. "Hence, if we see a planet that shows evidence for liquid water, we can immediately think about the possible presence of carbon-based life."
Currently, there is no federal funding to build a Terrestrial Planet Finder. However, this hasn't discouraged the amount of research related to exoplanets that researches have conducted over the recent years. Nevertheless, a TPF would be very useful in detecting life-sustaining planets. It allows for the detection of gases or the lack of it in a planet's atmosphere.
"Maybe every planet out there that has the right conditions develops life," Kasting said. "We don't really know the answer to that. But, it could be. If you're an optimist, you think it just takes the right conditions. It happened on Earth, why wouldn't it happen somewhere else?"
