Boffins believe terrestrial planets orbiting Sun-like stars in the
galaxy are probably more hospitable to life than Earth, thanks to their
balmy subsurface temperatures.

Tectonic plates meet under the Atlantic Ocean
From the stars found by the HARPS (High Accuracy Radial Velocity
Planet Searcher) spectrometer at the European South Observatory in
Chile, geoboffins and astroboffins selected two solar twins of our Sun -
stars roughly the same size, age and overall composition - and measured
the amounts of radioactive elements they contained, a key indicator of
their world-building abilities.
Elements such as thorium and uranium are essential because they help
heat up a planet's interior and power its plate tectonics. It is
believed these are needed to keep water - an ingredient for life - on
the surface of the world.
Seven of the eight twins studied so far possess more thorium than our
Sun, and if the planets orbiting in the habitable zone around those
stars inherited this material, they may have warmer interiors. This
means tectonic activity will have occurred for longer, giving life more
time to arise.
One star, for example, had 2.5 times more thorium than the Sun, and
the boffins now expect its habitable planets to be 25 per cent warmer
inside than Earth. The findings have also encouraged the scientists to
extend the habitable zones around each star, increasing the number of
prospectively life-packed Earth-like worlds.
"At this point, all we can say for sure is that there is some natural
variation in the amount of radioactive elements inside stars like
ours," Ohio State doctoral student Cayman Unterborn said.
"With only nine samples including the Sun, we can't say much about
the full extent of that variation throughout the galaxy. But from what
we know about planet formation, we do know that the planets around those
stars probably exhibit the same variation, which has implications for
the possibility of life."
The relationship between plate tectonics and surface water isn't
fully understood, but boffins do think that the same forces of heat
convection in the mantle that move the Earth's crust regulate the amount
of water in the oceans as well.
Microbial life in particular benefits from subsurface heat, with some
microbes on Earth living directly off that source for energy instead of
relying directly on the Sun.
To confirm its findings,
the team
wants to do a detailed statistical analysis of noise in the HARPS data
to improve the accuracy of their computer model. The boffins will then
ask for telescope time to look for more solar twins. ®