14 DAY TRIAL // According to the conclusions of a new study, alien planets in the super-Earth class may be less capable of supporting the emergence and development of life than previously thought. The differences between Earth- and super-Earth-class planets may simply be too large, the research suggests.
A super-Earth is an extrasolar planet that is heavier than our own, but lighter than Uranus and Neptune, which are the smallest gas giants in the solar system. Both of these worlds are around 15 times heavier than Earth, astronomers say.
Not all planets in this class have rocky surfaces, and it may turn out to be more appropriate to designate some of them as gas dwarfs. The designation super-Earth does not refer to the surface conditions or habitability characteristics of any planet it applies to.
In a statement, researchers at the Massachusetts Institute of Technology (MIT), in Cambridge, say that there is a significant probability that most super-Earths don't have a differentiated interior, as in a clear separation between core, mantle and crust.
This is absolutely necessary for plate tectonics to develop. This phenomenon in turn causes volcanism, seismic activity, tsunamis and a host of atmospheric processes that life needs in order to develop.
In addition, lacking a molten metal core would make the existence of a magnetosphere rather improbable, and you need to have such a magnetic shield in order to prevent ultraviolet radiation, stellar radiations and cosmic rays from battering the surface of the planet.
One important aspect to keep in mind about super-Earth is that the pressure levels at their cores are many times larger than those found inside Earth. This also means higher melting temperatures and viscosity for all materials present within.
“Current understanding is that the terrestrial planets in our solar system formed rapidly – in about the first 50 million years. The timescale of core formation depends strongly on viscosity,” MIT expert Vlada Stamenkovic explains, quoted by Space.
“The high melting temperatures and the large viscosities that we’ve calculated for super-Earths suggest either a slow core formation or no core formation at all,” adds the scientist, a member of the study team.
Even if cores, mantles and crusts could somehow develop inside super-Earths, the convection forces that drive plate tectonics would act extremely slow, allowing stagnant layers to form inside the mantle, and therefore reducing heat flow to the crust. This would mean that the surface would be very cold.