Water Less Likely to Support Life

Because liquid water—and the temperatures that permit it—are crucial for life as we know it, the search for extraterrestrial life focuses on places where liquid water may exist (or may have once existed). From Mars to extrasolar planets, evidence of water is almost always interpreted with enthusiasm by those who believe that a little water, the right organic compounds, and an awful lot of time are together sufficient for life to appear.

The presence of water, even if it’s in liquid form, isn’t enough for life to survive.

A new study appearing in the journal Astrobiology reminds scientists that the presence of water, even if it’s in liquid form, isn’t enough for life to survive. That’s the point made by the Australian National University’s Eriita Jones and Charles Lineweaver by closely studying our own planet.

The team’s survey of life on earth revealed that life exists in only twelve percent of the volume of this planet where water exists. The scientists considered not only the effect of temperature on whether liquid water exists in an environment, but also the influence pressure and salt have—both of which can alter the boiling and freezing points of water. As an example of their findings, the team argues that the absence of life in the upper atmosphere indicates that there is a low-pressure limit for life, despite the presence of water in the upper atmosphere. “Life and water are not equivalent,” explained Jones. “There may be a lot of liquid water that is hostile to life.”

In related news, astronomers using computer models have determined that some exoplanets thought to be habitable may not be so—at least, not all the time. “[A planet’s] habitable zone is very complicated,” said one of the scientists.1 Both of these studies remind us that earth is truly in a privileged position in our solar system and in the Milky Way. That privilege is one of the many evidences that shout “design.”