The Exploration of Space

NASA has a long legacy of space exploration. In the decades since its founding, the space agency has landed rovers on Mars, sampled the atmosphere of Jupiter, explored Saturn and Mercury – and even landed humans on the moon – to name a few.  Some missions, like the Kepler planet-hunting observatory, are relatively new, and only time will tell if they join the ranks of NASA’s finest flights.

Pioneer

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.

WMAP

NASA/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.

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.

Spirit & Opportunity

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.

Chandra

NASA, ESA, ESO, CXC, and D. Coe (STScI)/J. Merten (Heidelberg/Bologna)

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.

Viking

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.

Apollo

NASA, Charles M. Duke Jr.

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.