GREENBELT, Md., Nov. 30, 2017 /PRNewswire-USNewswire/ — Heat generated by the gravitational pull of moons formed from massive collisions could extend the lifetimes of liquid water oceans beneath the surface of large icy worlds in our outer solar system, according to new NASA research. This 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 Prabal Saxena of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, lead author of the research published in Icarus November 24. “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.”
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 less than 350 degrees below zero Fahrenheit (below minus 200 Celsius). However, there is evidence that some may have layers of liquid water beneath their icy crusts. In addition to bulk densities that are similar to other bodies suspected to have subsurface oceans, an analysis of the light reflected from some TNOs reveals signatures of crystalline water ice and ammonia hydrates. At the extremely low surface temperatures on these objects, water ice takes a disordered, amorphous form instead of the regularly ordered crystals typical in warmer areas, such as snowflakes on Earth. Also, space radiation converts crystalline water ice to the amorphous form and breaks down ammonia hydrates, so they are not expected to survive long on TNO surfaces. This suggests that both compounds may have come from an interior liquid water layer that erupted to the surface, a process known as cryovolcanism.
Most of the long-lived heat inside TNOs comes from the decay of radioactive elements that were incorporated into these objects as they formed. This heat can be enough to melt a layer of the icy crust, generating a subsurface ocean and perhaps maintaining it for billions of years. But as the radioactive elements decay into more stable ones, they stop releasing heat and the interiors of these objects gradually cool, and any subsurface oceans will eventually freeze. However, the new research found that the gravitational interaction with