NASA's 10 Greatest Science Missions

Clara Moskowitz, Staff Writer, SPACE.com

As missions go, the name Kepler might one day be just as

famous as Hubble or Apollo, which are legendary for

changing the course of history with their scientific

breakthroughs. NASA is set to launch the new planet-

hunting spacecraft tonight. If Kepler succeeds in its

mission to find a truly Earth-sized planet in a habitable

orbit around a distant sun, the discovery could change our

conception of our own place in the cosmos forever.

History will tell if Kepler is really one of the greats. For

now, here's our subjective list of ten NASA missions that

have already earned their spot in the space mission hall

of fame.

And if you don't like our choices, you can weigh in with

your own opinion in NASA's "Mission Madness"

tournament. Starting March 9, NASA will host online voting

matches that narrow down to a final contest deciding

which of 64 historic missions will take home the title

"greatest."

10. Pioneer

Pioneer 10 and Pioneer 11, launched in 1972 and 1973,

respectively, were the first spacecraft to visit the solar

system's most photogenic gas giants, Jupiter and Saturn.

...

9. Voyager

Shortly after the Pioneers made their flybys, the Voyager

1 and Voyager 2 probes followed. ... Voyager went on to

make the first flybys of Uranus, where it discovered 10

new moons, and Neptune, where it found that Neptune

actually weighs less than astronomers thought. ...

8. WMAP

The Wilkinson Microwave Anisotropy Probe (WMAP),

launched in 2001, may not be as well-known, but it

measures with unprecedented accuracy the temperature 

of the radiation left over from the Big Bang. By mapping

out the fluctuations in the so-called cosmic microwave

background radiation, the spacecraft has heralded a leap

forward in cosmological theories about the nature and 

origin of the universe. Among other revelations, the data

from WMAP revealed a much more precise estimate for

the age of the universe — 13.7 billion years — and

confirmed that about 95 percent of it is composed of

poorly understood things called dark matter and dark

energy.

7. Spitzer

Another spacecraft with a profound effect on cosmology

and astrophysics is the Spitzer Space Telescope, which observed the heavens through infrared light. ...

6. Spirit & Opportunity

Intended for just a 90-day mission, these workhorse Mars rovers have far outdone themselves, and are still chugging away on the red planet more than five years after landing. ... 

5. Cassini-Huygens

This joint NASA/ESA spacecraft, launched in 1997, reached its destination, Saturn, in 2004. ... 

4. Chandra

Since 1999, the Chandra X-ray Observatory has been scanning the skies in X-ray light, looking at some of the most distant and bizarre astronomical events. ...

3. Viking

When NASA's Viking 1 probe touched-down on Mars in July 1976, it was the first time a man-made object had soft-landed on the red planet. ...

2. Hubble

The most-loved of all NASA spacecraft, the Hubble Space

Telescope has name recognition around the world. Its

photos have changed the way everyday people figure

themselves into the cosmos. The observatory has also

radically changed science, making breakthroughs on

astronomical issues too numerous to count. By finally

sending up an optical telescope to peer at the sky from

beyond Earth's turbulent atmosphere, NASA developed a

tool that could reveal stars, planets, nebulae and galaxies 

in all their fully-detailed glory.

1. Apollo

NASA's best space science mission? The one humans

got to tag along on, of course! Not only was sending a

man to the moon monumental for human history, but the

Apollo trips were the first to bring celestial stuff back to

Earth and greatly advanced our scientific understanding

of the moon. Before Apollo, many people weren't even

convinced the moon wasn't made out of cheese (well...

non-scientists at least). By studying the moon up close

and personal, and then carting loads of moon rocks home,

the Apollo astronauts gathered data that helped us learn

how old the moon is, what it's made out of, and even how

it might have begun.

New Video - Kepler: Hunting Alien Earths 

Top 10 Most Intriguing Extrasolar Planets 

New Video - How NASA's Kepler Spacecraft Will Launch 

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