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. Pioneer 10 was the first probe to
travel through the solar system's asteroid belt, a field of orbiting rocks
between Mars and Jupiter. Then about a year-and-a-half after its launch, the
spacecraft made the first flyby of the planet Jupiter. It took stunning
up-close photos of the Great Red Spot and the wide swaths of red that band the
planet. About a year later, Pioneer 11 flew by Jupiter, and then moved on to
Saturn, where it discovered a couple of previously unknown small moons around
the planet, and a new ring. Both probes have stopped sending data, and are
continuing out on their one-way
voyages beyond the solar system.
9. Voyager
Shortly after the Pioneers made their flybys, the Voyager
1 and Voyager 2 probes followed. They made many important discoveries about
Jupiter and Saturn, including rings around Jupiter and the presence of
volcanism on Jupiter's moon, Io. 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. Both Voyager crafts have
enough power to keep transmitting radio signals until at least 2025, and are
now exploring the very edge
of the solar system and beginning of interstellar space. Voyager 2 is
currently the farthest man-made object from Earth, at more than a hundred times
the distance from the Earth to the sun, and more than twice as far as Pluto.
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. This light, which has a longer wavelength than visual
light, is mostly blocked by Earth's atmosphere. In addition to taking
gorgeous photos of galaxies, nebulae and stars, the telescope has made
numerous groundbreaking scientific discoveries. In 2005 Spitzer became the
first telescope to detect light from extrasolar planets (most of these distant
worlds are detected only through secondary, gravitational effects on their
suns). In another observation, astronomers think the telescope may have even
captured light from some of the first stars born in the universe.
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. Spirit and Opportunity, the twin
Mars Exploration Rovers, landed on opposite sides of the planet in January
2004. Since then, they have been traveling all over the surface, poking into
craters and roving over unexplored hills. Among their major finds is evidence
that the surface of Mars once had liquid water. (A tip of the hat to Sojourner
rover, which brought full-color close-ups of Mars in 1997, just as the Internet
was becoming wildly popular, thereby earning a special place in the hearts of
millions who enjoyed unprecedented access to NASA mission photos.)
5. Cassini-Huygens
This joint NASA/ESA spacecraft, launched in 1997, reached
its destination, Saturn, in 2004. Since then it has been in orbit
around the ringed world, taking one stunning snapshot after another of the
planets rings, moons and weather. The Hugyens probe separated from Cassini and
made a special trip to the moon Titan, where it descended through the
atmosphere and landed on solid ground in 2005. Though previous spacecraft have
visited Saturn, Cassini is the first to orbit it and study the system in
detail.
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. Because Earth's pesky atmosphere blocks
out most X-rays, astronomers couldn't view the universe in this high-energy,
short-wavelength light until they sent Chandra up to space. The observatory has
such high-resolution mirrors, it can see X-ray sources 100 times fainter than
any previous X-ray telescope. Among other firsts, Chandra showed scientists the
first glimpse of the crushed star left over after a supernova when it observed
the remnant Cassiopeia A.
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. (Though the Soviet Mars 2 and 3 probes did land on the
surface, they failed upon landing). The Viking 1 lander also holds the title of
longest-running Mars surface mission, with a total duration of 6 years and 116
days. The spacecraft also sent the first color pictures back from the Martian
surface, showing us what that mysterious red dot looks like from the ground for
the first time.
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.
advertisement
