In a boost to the search for alien life, a new NASA study suggests that some icy worlds in our outer solar system, including Pluto, may harbour liquid water oceans beneath the surface.
Heat generated by the gravitational pull of moons formed from massive collisions could extend the lifetimes of liquid water oceans beneath the surface of these large icy worlds, said the study published in the journal Icarus.
These frigid worlds are found beyond the orbit of Neptune and include Pluto and its moons.
They are known as Trans-Neptunian Objects (TNOs) and are far too cold to have liquid water on their surfaces, where temperatures are below minus 200 degrees Celsius.
However, there is evidence that some may have layers of liquid water beneath their icy crusts.
"We found that tidal heating can be a tipping point that may have preserved oceans of liquid water beneath the surface of large TNOs like Pluto and Eris to the present day," said study co-author Wade Henning of NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The finding greatly expands the number of locations where extraterrestrial life might be found, since liquid water is necessary to support known forms of life and astronomers estimate there are dozens of these worlds.
"These objects need to be considered as potential reservoirs of water and life," said lead author of the research Prabal Saxena of NASA.
"If our study is correct, we now may have more places in our solar system that possess some of the critical elements for extraterrestrial life," Saxena added.
The team used the equations for tidal heating and calculated its contribution to the "heat budget" for a wide variety of discovered and hypothetical Trans-Neptunian Objects-moon systems, including the Eris-Dysnomia system. Eris is second-largest of the currently known TNOs after Pluto.
The researchers found that the gravitational interaction with a moon can generate enough heat inside a Trans-Neptunian Object to significantly extend the lifetime of a subsurface ocean.