Space Telescope Science
Astronomers using the Hubble Space Telescope have gone looking for water vapor in the atmospheres of three planets orbiting stars similar to the Sun – and have come up nearly dry. The planets spectroscopically surveyed have only one-tenth to one one-thousandth the amount of water predicted by standard planet-formation theories. The planets are not habitable because they are gaseous and are as big as Jupiter. They lie so much closer to their host star than Jupiter is to our Sun, so their atmospheres are seething between 1,500 and 4,000 degrees Fahrenheit. Nevertheless, this result suggests that some percentage of Earth-size exoplanets may be more deficient in water than predicted. And, water is a necessary prerequisite for life as we know it. The search for water-bearing terrestrial worlds may be more challenging than thought for future space telescopes. And, scientists may have to revisit their theories of planet formation.