Light transmitted and partially absorbed - CNET News

"Using the Hubble Space Telescope's powerful Wide Field Camera 3, which is capable of peering at exoplanets trillions of miles away, two teams of scientists have found faint signatures of water in the atmospheres of five distant planets.

The strengths of the water signatures varied on the five planets WASP-17b, HD209458b, WASP-12b, WASP-19b, and XO-1b. Each orbit a star, allowing for observation. WASP-17b and HD209458b had the strongest signals, but the readings from the other three planets -- WASP-12b, WASP-19b and XO-1b -- also are consistent with evidence of water."