After the space shuttle Challenger broke apart moments after launch on January 28, 1986, NASA suffered through its darkest days and was brought to task for a series of missteps that led to the disaster. The tragedy changed the space program forever. But after a nearly three-year moratorium on shuttle flights, NASA returned to orbit and has since moved on to new triumphs and innovations in space exploration.
Launched May 4, 1989, the Magellan spacecraft was sent to Venus to make the first global map of the planet's surface and gravity field. Magellan made it to Venus in 1990 and after orbiting for four years, the spacecraft intentionally flew down toward the planet's surface in order to gather data on its atmosphere.
Hubble Space Telescope
The Hubble Space Telescope was launched April 24, 1990 and is still going strong a quarter-century later. Hubble got off to a rocky start, but after a successful 1993 mission to fix its flawed mirror, it did a lot to popularize astronomy, giving Earthlings an unprecedented glimpse at the cosmos, like the iconic "Pillars of Creation" image of stars forming in the Eagle Nebula, seen here.
More Photos: 25 years of breathtaking Hubble Telescope images
Galileo was launched October, 18, 1989 to study Jupiter and its moons. En route to the giant planet, Galileo made a series of unprecedented discoveries. It visited two asteroids -- Gaspra and Ida; made direct observations of a comet shooting past; and took infrared images of Venus's clouds as it zoomed by. Once it approached Jupiter, Galileo found saltwater beneath the surface of its moon Europa, found volcanoes on the moon Io, as well as a magnetic field generated by the moon Ganymede. The mission came to a close in 2003 when the probe was sent plummeting to Jupiter's surface in order to prevent an impact with Europa.
Ulysses launched October 6, 1990, on what was meant to be a five-year mission to look at the Sun's north and south poles. This mission ended up extending far beyond its initial termination time, as it captured data on various aspects of the sun -- from solar wind to interstellar dust -- before ending in 2009.
Launched August 10, 1992, the Topex/Poseidon was a satellite that spent more than 13 years in orbit around the Earth, gathering data on the planet's ocean circulation and how that affected the overall global climate. The satellite also helped researchers understand the El Niño phenomenon. This marked a collaboration between NASA and France's National Center for Space Studies (CNES).
"The camera that saved Hubble"
Installed in December 1993 by astronauts from the space shuttle Endeavour, the Wide Field and Planetary Camera 2 (WFPC2), is called "the camera that saved Hubble." This camera replaced one with a defective mirror and became the main imaging instrument on the Hubble Space Telescope, producing more than 135,000 images of the universe, until it was replaced in 2009.
Mars Global Surveyor
The Mars Global Surveyor was launched November 7, 1996 and remained in operation for more than nine years, orbiting the Red Planet. Its mission was to study the composition of the planet and its weather patterns, and to map its topography. One big discovery? The surveyor found evidence of liquid water at or near Mars' surface.
Mars Pathfinder/Sojourner Rover
Launched December 4, 1996, the Mars Pathfinder mission marked the first time a wheeled vehicle was used on any other planet in the solar system besides Earth. The Sojourner rover landed on the Martian surface and spent 83 days -- the planned mission was for just seven days -- exploring the terrain and taking unprecedented photos of Mars.
Launched October 15, 1997, the Cassini spacecraft has become one of NASA's most iconic space exploration missions. The spacecraft was sent to orbit Saturn and its moons. Cassini is currently in its second extended mission, which continues through 2017.
More Photos: Cassini captures Saturn and its moons
Deep Space 1
Launched October 24, 1998, Deep Space 1 was designed to test out new technologies like an ion engine to propel spacecrafts. The mission expanded beyond its initial goals, flying by the asteroid 9969 Braille and the comet Borelly, producing some of the best images ever taken of an asteroid or a comet.
Stardust was launched February 7, 1999, and was the first spacecraft to retrieve and return a comet sample and extraterrestrial material from outside the orbit of the moon.
The Active Cavity Irradiance Monitor Satellite, or AcrimSat, mission was launched December 20, 1999. The satellite spent 14 years orbiting Earth, monitoring sun radiation and its effects on the planet.
Shuttle Radar Topography Mission
The Shuttle Radar Topography Mission, launched February 11, 2000, flew aboard NASA's Space Shuttle Endeavour during an 11-day mission. The result? The first near-global topographical map ever made of Earth. The mission gathered information on nearly 80 percent of the planet's land surfaces.
Launched April 1, 2001, the Mars Odyssey spacecraft has spent more time in Martian orbit than any other spacecraft in history and is still going strong.
Genesis was launched August 8, 2001 and was designed to collect solar wind samples. It marked NASA's first material collection beyond the moon. Using this material, scientists determined that Earth possibly was created out of different solar nebula materials than those that formed the sun.
Galaxy Evolution Explorer
The Galaxy Evolution Explorer was launched April 28,2003. The orbiting space telescope was designed to observe the universe in ultraviolet wavelengths in order to measure the history of star formation.
Spitzer Space Telescope
The Spitzer Space Telescope was launched August 25, 2003 and was meant to be something of a cousin to Hubble. Its goal: to study the early universe in infrared light. This was the first telescope to view light from a planet outside our own solar system.
Launched January 12, 2005, Deep Impact's mission was like something out of an action-packed sci-fi movie. Its planned July 4, 2005 impact with comet Tempel 1 generated a bright flash of light that was determined to be ice and dust debris issuing from a deep impact crater. This mission marked the first-ever attempt to look beneath the surface of an actual comet.
New Horizons Pluto Fly-by
The New Horizons probe launched January 19, 2006, on a mission to photograph the distant, icy, dwarf planet Pluto. Over the next nine and a half years, it flew some three billion miles to reach its target, making a dramatic fly-by Pluto in July 2015. The spacecraft sent back astonishing, detailed images of the surface of Pluto and its moons.
More Photos: Astonishing Pluto in sharp focus
Launched August 4, 2007, Phoenix was a lander sent off to Mars' surface to search for evidence of past microbial life on the Red Planet. During its mission, Phoenix discovered evidence of perchlorate, a potential energy source for microbes.
Dawn was launched September 27, 2007 to orbit "protoplanet" Vesta. It is now currently in orbit around dwarf planet Ceres.
Kepler Space Telescope
Launched March 6, 2009, Kepler is a space telescope on a mission to scan a portion of the Milky Way for Earth-size planets. The goal is to find planets that could potentially be hospitable to life.
Herschel Space Observatory
The Herschel Space Observatory, launched May 14, 2009, used infrared light to examine some of the darkest and coldest regions in the universe. This yielded new understandings about galaxies, dark matter, and other "cosmic mysteries," according to NASA.
NASA's NEOWISE program utilizes a space telescope to seek out asteroids and comets, particularly any that could be threatening to Earth, using the Wide-field Infrared Survey Explorer (WISE) spacecraft launched into low Earth orbit on December 14, 2009. During a planned three-year survey -- December 2013 through 2016 -- NEOWISE will identify and characterize near-Earth objects, gathering data on their size and other key measurements.
Launched June 10, 2011, Aquarius gave NASA its first global observations of Earth's sea surface salinity. This gave climatologists a better grasp of the ocean's role in the planet's water cycle, climate variability, and overall weather patterns.
The Juno spacecraft was launched August 5, 2011, and is heading to Jupiter. It is scheduled to arrive July 4, 2016, and will be the first time that NASA can look below the giant planet's dense cloud cover.
Mars Curiosity Rover
Launched November 26, 2011, the Mars Curiosity rover is the most technologically advanced rover ever built. It landed in the Red Planet's Gale Crater August 5, 2012. Curiosity is dedicated to understanding more about the planet, and whether it has ever contained -- or might currently be home to -- microbial life.
Nuclear Spectroscopic Telescope Array
The Nuclear Spectroscopic Telescope Array, or NuSTAR, mission was launched June 13, 2012. The goal is to study the universe in high energy X-rays to better understand the dynamics of black holes, exploding stars and the most extreme active galaxies.
So what's next? On its website, NASA outlines 10 planned missions for the future, and three proposed missions that are still speculative. From placing a lander on Mars that will drill beneath the surface to the proposed Europa mission that will send a spacecraft to explore Jupiter's icy moon, we will have to stay tuned to find out what discoveries NASA makes next.
More Photos: The Challenger disaster