5 planets most likely to be on Elon Musk's itinerary (pictures)

If Elon Musk and SpaceX are looking to inhabit far away worlds, it might make sense to find the most Earth-like places possible, with virgin air and untouched water. With the recent discovery of water on distant exoplanets, we might be one step closer to that reality.

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.

The presence of atmospheric water was reported previously on a few exoplanets orbiting stars beyond our solar system, but this is the first study to measure conclusively and compare the profiles and intensities of these signatures on multiple worlds.

NASA scientists found faint signals of water in the atmospheres of five distant planets orbiting three different stars. All five planets appear to be hazy. This NASA illustration shows a star's light illuminating the atmosphere of a planet.

NASA says the water signatures were all less pronounced than expected, possibly because a layer of haze or dust in the atmosphere blankets each of the five planets.

This haze can reduce the intensity of all signals from the atmosphere in the same way fog can make colors in a photograph appear muted. At the same time, haze alters the profiles of water signals and other important molecules in a distinctive way.

"To actually detect the atmosphere of an exoplanet is extraordinarily difficult. But we were able to pull out a very clear signal, and it is water," said L. Drake Deming of the University of Maryland in College Park.

Astronomers then spread the star's light into its distinct spectrum of colors to see which wavelengths have been absorbed. The dark absorption bands act as molecular fingerprints, revealing the atmosphere's chemical makeup.

This artist's impression shows a dramatic closeup of the extrasolar planet XO-1b passing in front of a Sun-like star 600 light years from Earth. The Jupiter-sized planet is in a tight, four-day orbit around the star.

HD 209458 b, depicted here in an artist's illustration, is an extrasolar planet that orbits the Solar analog star HD 209458 in the constellation Pegasus, some 150 light years from Earth's solar system.

HD 209458 b itself is notable as it was the first of many categories in exoplanet discovery, including the first transiting extrasolar planet discovered, the extrasolar planet known to have an atmosphere, and the first extrasolar planet found to have an atmosphere containing oxygen and carbon.