Scientists, at the Goldschmidt Conference in Boston, have shown that exoplanets (planets that orbit other stars) have a substantial amount of water. This will significantly impact the search for life in our galaxy. Exoplanets were discovered in 1992 and and encouraged scientists to understand the compositions of these planets, and to see if they are suitable for development of life.
The evaluation of data obtained from the Kepler Space Telescope and the Gaia mission suggests that many of these known planets might contain as much as 50% water- this compared to Earth’s 0.02% water content is huge. “It was a huge surprise to realize that there must be so many water-worlds”, said lead researcher Dr Li Zeng from Harvard University.
Scientists say that out of these 4000 confirmed or potential exoplanets discovered as of yet can be categorized into two groups: those with the average planetary radius around 1.5 that of Earth, and those with an average radius of around 2.5 times that of Earth. After analyzing the data about the exoplanets with mass measurements and recent radius measurements from the Gaia satellite, an international group of scientists have developed a new model of the internal structure of the exoplanets.
“We have looked at how mass relates to radius, and developed a model which might explain the relationship”, added Li Zeng. The model indicates that those exoplanets which have a radius of around x1.5 Earth radius tend to be rocky planets (of typically x5 the mass of the Earth), while those with a radius of x2.5 Earth radius (with a mass around x10 that of the Earth) are probably water worlds”.
“This is water, but not as commonly found here on Earth”, continued Li Zeng. “Their surface temperature is expected to be in the 200 to 500 degree Celsius range. Their surface may be shrouded in a water-vapor-dominated atmosphere, with a liquid water layer underneath. Moving deeper, one would expect to find this water transforms into high-pressure ices before we reaching the solid rocky core. The beauty of the model is that it explains just how composition relates to the known facts about these planets”.
Li Zeng also added “Our data indicate that about 35% of all known exoplanets which are bigger than Earth should be water-rich. These water worlds likely formed in similar ways to the giant planet cores (Jupiter, Saturn, Uranus, Neptune) which we find in our own solar system. The newly-launched TESS mission will find many more of them, with the help of ground-based spectroscopic follow-up. The next generation space telescope, the James Webb Space Telescope, will hopefully characterize the atmosphere of some of them. This is an exciting time for those interested in these remote worlds”.