1. Alan Shepard
Alan Shepard sparked a generation of aspiring astronauts with the United States' first manned space flight on May 5, 1961. That same month President John F. Kennedy stoked the space craze, announcing that an American would walk on the moon within the decade. Fifty years on, despite budget stress and competing priorities, it's still clear that the giant leaps continue.
2. International Space Station
Voilà! Earth's first off-planet residence, the International Space Station, will be complete after 10 years of continuous habitation and construction. Our outer-space home base plans to welcome new arrivals until 2020, including a talking robot that will keep astronauts company and tweet updates back home.
3. SpaceX's Dragon
After the space shuttle program ends this summer, privately built craft will soar into the same flight path: NASA has contracted with the firm SpaceX to use its Dragon spacecraft on supply runs to the space station.
4. Virgin Galactic
Spaceport America will open in New Mexico by the end of the year, ushering in the era of recreational space travel. There, Virgin Galactic will continue test flights for its commercial shuttles. Soon passengers can venture on a 2.5-hour journey to the edge of outer space, 62 miles from terra firma. So far, about 410 people have plunked down deposits for the $200,000 ticket.
5. Delta 2
In September, multiple unmanned probes will hitch a ride to the moon on a Delta 2 rocket. One will collect data on the moon's atmosphere and clingy dust — information important for future manned missions there.
In March, NASA's MESSENGER became the first spacecraft to go into orbit around Mercury, where it will continue its up-close study of the planet's origins.
7. Curiosity Rover
This fall, NASA's appropriately named Curiosity rover will launch toward Mars to dig up data on the red planet's deepest mystery: Has Mars ever been habitable?
Spacecraft Juno will begin its five-year cruise toward Jupiter in August. When it arrives, the probe will orbit the planet 32 times, measuring its composition, atmosphere and magnetosphere. The goal? Understanding how our solar system — and its largest planet — formed.
9. STEREO Probes
Here comes the sun! In February, NASA's twin STEREO probes began beaming back images taken from opposite sides of our star, providing the first-ever 360-degree views. Observing the full sun will enable scientists to develop an alert system for events called coronal mass ejections, eruptions that interfere with Earth's satellites and power grids.
The NASA Kepler space telescope's search for planets outside our solar system found 1,235 new candidates. The five most intriguing are similar to Earth in size and temperature — in other words, possibly habitable.
10. Michio Kaku
What's next? Eminent physicist Michio Kaku says the big space news of the coming 50 years will be confirming that we are not alone in the universe. "We'll find planets with oceans, oxygen in the atmosphere, microbial life and maybe even intelligent life," Kaku says. "Perhaps we'll even be able to eavesdrop on their conversations." (Read the full interview.)