text: There at least 200 billion Earth-like planets in our galaxy – and now Nasa officials claim we could be on the verge of finding life on one of them. During a talk in Washington today, the space agency announced that humanity is likely to encounter extra-terrestrials within a decade. 'I believe we are going to have strong indications of life beyond Earth in the next decade and definitive evidence in the next 10 to 20 years,' Ellen Stofan, chief scientist for Nasa, said. Scroll down for video . During a talk today, Nasa announced that humanity will encounter extra-terrestrials within a decade. 'I believe we are going to have strong indications of life beyond Earth in the next decade and definitive evidence in the next 10 to 20 years,' said Ellen Stofan, chief scientist for Nasa, (pictured) at a Washington panel discussion . 'We know where to look, we know how to look, and in most cases we have the technology.' Jeffery Newmark, interim director of heliophysics at the agency, added: 'It's definitely not an if, it's a when.' 'We are not talking about little green men,' Stofan said. 'We are talking about little microbes.' The announcement has been prompted by the recent discovery of water by Nasa in surprising places. Jim Green, director of planetary science at Nasa, noted that a recent study of the Martian atmosphere found 50 per cent of the planet's northern hemisphere once had oceans a mile deep. Scientists using the Hubble recently provided powerful evidence that Jupiter's moon Ganymede (pictured) has a saltwater, sub-surface ocean, likely sandwiched between two layers of ice . The same study found that water had been present on the red planet for up to 1.2 billion year. 'We think that long period of time is necessary for life to get more complex,' Stofan said. Nasa associate administrator John Grunsfeld said he is excited about seeing what form life beyond Earth may take. In their hunt for alien life, astronomers have so far focused on looking for Earth-like planets around smaller, cooler suns. But these exoplanets - despite having a chance of holding water - are believed to be locked in a rotation around their sun which causes only one side of their surface face the star. Now astronomers claim that such exoplanets actually rotate around their stars, and spin at such a speed that they exhibit a day-night cycle similar to Earth – increasing the chance of finding alien life. Planets with potential oceans could have a climate that is much more similar to Earth's than previously expected,' said Jérémy Leconte, a postdoctoral fellow at the Canadian Institute for Theoretical Astrophysics (CITA) at the University of Toronto. 'If we are correct, there is no permanent, cold night side on exoplanets causing water to remain trapped in a gigantic ice sheet,' he said. 'Whether this new understanding of exoplanets' climate increases the ability of these planets to develop life remains an open question.' 'Once we get beyond Mars, which formed from the same stuff as Earth, the likelihood that life is similar to what we find on this planet is very low,' he said. 'I think we're one generation away in our solar system, whether it's on an icy moon or on Mars, and one generation [away] on a planet around a nearby star. Scientists using the Hubble recently provided powerful evidence that Jupiter's moon Ganymede has a saltwater, sub-surface ocean, likely sandwiched between two layers of ice. Jupiter's moon Europa and Saturn's satellite Enceladus are also thought to have an ocean of liquid water beneath their surface in contact with mineral-rich rock. This, according to Nasa, means they may have the three ingredients needed for life as we know it. 'The science community is making enormous progress,' said Green. 'And I've told my team I'm planning to be the director of planetary science when we discover life in the solar system. At the same conference last year, Nasa Administrator Charles Bolden made a more conservative estimate. He claimed that we will find life within the next 20 years - with a high chance it will be outside our solar system. Nasa next Mars rover, scheduled to launch in 2020, will search for signs of past life and bring samples for a possible return to Earth for analysis. New Horizons took this image of the icy moon Europa rising above Jupiter's cloud tops. The space agency is planning a mission to Europa, which may launch as early as 2022, to find out whether the moon is habitable . Nasa also hopes to land astronauts on Mars in the 2030s, which Stofan says is crucial key to the search for Mars life. 'I'm a field geologist; I go out and break open rocks and look for fossils,' Stofan said. 'Those are hard to find. 'So I have a bias that it's eventually going to take humans on the surface of Mars — field geologists, astrobiologists, chemists — actually out there looking for that good evidence of life that we can bring back to Earth for all the scientists to argue about.' The space agency is also planning a mission to Europa, which may launch as early as 2022. It hopes to find out whether the icy moon is habitable. Meanwhile, the agency's James Webb Space Telescope (JWST), will launch in 2018 to scope out the atmospheres of nearby 'super-Earth' alien planets.
target: The comment was made today by Ellen Stofan, chief Nasa scientist .
  'It's definitely not an if, it's a when,' added Nasa's Jeffery Newmark .
  But the likelihood that life is similar to that on Earth is low, they said .
  Signs of water have been found on some of Jupiter and Saturn's moons .