Addressing a panel discussion earlier this week on the space agency's search for habitable worlds and alien life, NASA chief scientist Ellen Stofan said: "I think we are going to have strong indications of life beyond Earth within a decade, and I think we are going to have definitive evidence within 20 to 30 years."
Recent discoveries suggest that the solar system and broader Milky Way galaxy teem with environments that could support life as we know it.
For example, oceans of liquid water slosh beneath the icy shells of the Jupiter moons Europa and Ganymede, as well as that of the Saturn satellite Enceladus.
"Oceans covered much of Mars in the ancient past, and seasonal dark streaks observed on the Red Planet's surface today may be caused by salty flowing water," Stofan added.
NASA's Curiosity rover has found carbon-containing organic molecules and "fixed" nitrogen, basic ingredients necessary for Earth-like life on the Martian surface, Space.com reported.
NASA's Kepler space telescope suggest that nearly every star in the sky hosts planets -- and many of these worlds may be habitable.
"We can see water in the interstellar clouds from which planetary systems and stellar systems form. We can see water in the disks of debris that are going to become planetary systems around other stars," informed Paul Hertz, director of NASA's Astrophysics Division.
NASA's next Mars rover, scheduled for launch in 2020, will search for signs of past life and cache samples for a possible return to Earth for analysis.
NASA also aims to land astronauts on Mars in the 2030s.
It is also planning a mission to Jupiter's moon Europa which may launch as early as 2022.
"I think we are one generation away in our solar system, whether it is on an icy moon or on Mars, and one generation (away) on a planet around a nearby star," noted former astronaut John Grunsfeld, associate administrator for NASA's Science Mission Directorate.