InSight, which stands for Interior Exploration using Seismic Investigations, is the first mission to study Mars' deep interior. After placing the first seismometer on another planet on Dec. 19, 2018 and detecting a number of seismic signals, InSight gathers data on what is likely the first quake ever observed on another planet on April 6, 2019. This first “marsquake” is very faint. But as InSight detects larger marsquakes in the future, scientists can use them to study Mars' deep interior. Understanding the interior structure of Mars can teach us how all rocky bodies in the Solar System are formed, including our home planet Earth and its Moon. When InSight blasted off on a United Launch Alliance Atlas V 401 rocket from Vandenberg Air Force base on May 5, 2018, it was also the first interplanetary mission launched from the West Coast.

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As NASA's InSight spacecraft touches down on the surface of Mars at 11:52:59 a.m. PST (2:52:59 p.m. EST), two briefcase-sized spacecraft are in perfect position to relay InSight's signals back to Earth. The two Mars Cube One (MarCO) CubeSats -- MarCO-A and MarCO-B, nicknamed EVE and Wall-E -- launched on the same rocket as InSight as a technology demonstration. They prove that small satellites can travel to deep space and successfully carry out communications and navigation experiments. After capturing the first image of Earth and the Moon ever taken by a CubeSat on May 9, 2018, MarCO-B (Wall-E) tops that with the first image of Mars ever taken by a CubeSat. During the flight past the Red Planet, and on Nov. 26, it also captures a grander image looking back at Mars that shows the planet’s surface features.

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Installed on the International Space Station in May 2018, NASA’s Cold Atom Laboratory (CAL) is the first experiment to produce a fifth state of matter in Earth orbit. Known as Bose-Einstein condensates, these ultracold clouds of atoms hover just above absolute zero, and exhibit strange and unique properties compared to the other four states of matter -- solids, liquids, gases and plasmas. In the microgravity environment of the International Space Station, Bose-Einstein condensates can reach colder temperatures compared to those produced by ground-based experiments, and scientists can observe freely evolving Bose-Einstein condensates for longer periods of time. CAL is a dedicated fundamental physics facility that allows researchers to use ultracold gasses in microgravity to probe a variety of natural phenomena.

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The Gravity Recovery and Climate Experiment Follow-On mission (GRACE-FO), designed to track how masses of liquid water and ice are changing on Earth, carries a technology demonstration onboard known as the laser ranging interferometer. This instrument -- installed on both of the twin GRACE-FO spacecraft -- precisely tracks changes in the distance between the spacecraft. These data are analyzed to create monthly global maps of changes in mass, such as water, on the planet. While the original GRACE mission used microwaves to track these changes, GRACE-FO is the first to use lasers for this measurement, improving its precision.

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In a fiery end to a 13-year tour of the Saturn system, the Cassini spacecraft hurtles into the atmosphere of the Ringed Planet at about 70,000 mph (113,000 kilometers per hour). Since Cassini is venturing closer to Saturn than any previous spacecraft, the mission keeps eight of its instruments on to take data all the way down and relays these data in near-real-time back to Earth as long as Cassini's antenna can stay pointed at our home planet. The spacecraft holds its own for 91 seconds against Saturn's atmosphere and stops communicating at 4:55 a.m. PDT (7:55 a.m. EDT) via NASA's Deep Space Network antenna complex in Canberra, Australia. Mission controllers send Cassini intentionally into Saturn to ensure that Saturn's moons -- in particular Enceladus, with its subsurface ocean and signs of hydrothermal activity -- remain pristine for future exploration.

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The Cassini spacecraft begins its “grand finale”—the final chapter of its remarkable 20-year-long journey in space—by exploring a unique region no other spacecraft has ever ventured into. The spacecraft dives through an approximately 1,500-mile-wide (2,400-kilometer-wide) gap between Saturn and its rings for the first time on April 26 and loops around to shoot through that gap another 21 times before ending its mission by burning up in the skies of Saturn on Sept. 15, 2017. Data from Cassini's grand finale provide insight into the planet's internal structure, rings, radiation environment and atmosphere (including the first direct measurements).

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Forty light-years away, a system of seven Earth-sized planets encircle an ultra-cool dwarf star called TRAPPIST-1. This is the only known planetary system apart from our own that has three planets in the habitable zone, the area around a star in which a planet could support liquid water on its surface. In collaboration with several ground-based telescopes, including the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, NASA's Spitzer Space Telescope helped reveal the number and nature of these planets, using its infrared vision.

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After traveling 1.7 billion miles (2.7 billion kilometers) and nearly five years, Juno successfully begins orbiting the solar system's largest planet on Independence Day. It is the first solar-powered spacecraft to explore Jupiter and carries instruments that will enable it to peer down through the clouds and into the planet's interior, giving scientists clues about how Jupiter was born and how the entire solar system evolved.

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Two-and-a-half years after it left its first destination, the protoplanet Vesta, NASA's Dawn spacecraft slips into orbit around Ceres, the largest world in the main asteroid belt between Mars and Jupiter. The spacecraft is approximately 38,000 miles (61,000 kilometers) from Ceres when it is captured by Ceres' gravity. Dawn shows Ceres to be a heavily cratered world that was geologically active in the recent past, with many intriguing features such as a tall isolated mountain and numerous patches of bright material.

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Astronomers using the NuSTAR high-energy space telescope detect a pulsating, dead star beaming with the energy of about 10 million Suns. This is the brightest pulsar -- a dense stellar remnant left over from a supernova explosion -- ever recorded. The pulsar, which is named M82 X-2, is 12 million light-years away from Earth, in a galaxy called Messier 82.

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The Orbiting Carbon Observatory-2 (OCO-2) is NASA's first spacecraft dedicated to studying atmospheric carbon dioxide, which is the leading human-produced greenhouse gas responsible for warming our world. OCO-2 collects its first measurements on Aug. 6, as it flies over central Papua New Guinea and goes on to return almost a million measurements each day. These data are analyzed by scientists around the world to identify the sources emitting carbon dioxide into the atmosphere and the natural processes at Earth’s surface that are currently absorbing almost half of the carbon dioxide emitted by human activities. This information is crucial for understanding how rapidly the concentration of this gas will increase in the future as the global carbon cycle responds to climate change.

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NASA's Curiosity rover bores into a flat, veiny, sedimentary rock on Mars to collect a sample from its interior. An analysis of this rock sample in Gale Crater shows that ancient Mars could have supported living microbes. Rock powder collected by the drill was delivered into onboard laboratory instruments, which detected the key chemical ingredients for life, as well as the kind of energy gradient many microbes on Earth exploit to live. This site was once the bed of an ancient, freshwater lake.

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The Gravity Recovery and Interior Laboratory (GRAIL) mission uses twin NASA probes orbiting Earth's Moon to generate the most detailed gravity field map of any celestial body. The data reveal an abundance of features never before seen in detail, including tectonic structures, volcanic landforms, basin rings, crater central peaks and numerous simple, bowl-shaped craters. They also show that changes in the Moon's gravity field sync up with surface topography features. Using techniques similar to the GRACE mission circling Earth, GRAIL's twin spacecraft fly in formation, allowing scientists to use the changing distances between them as a way to discern areas of greater and lesser gravity on the Moon.

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A chance burst of material from the Sun, which makes the environment around Voyager 1 vibrate, allows the spacecraft to sense that it is in interstellar space, or the space between stars. The pitch of these vibrations -- which Voyager 1 "hears" in April 2013 -- helps scientists extrapolate back to when the spacecraft first crossed over into interstellar space, a denser environment than the one inside the bubble our sun blows around itself. Voyager scientists say the spacecraft left our solar bubble on Aug. 25, 2012, when it was 11.3 billion miles (18.3 billion kilometers) away from the Sun.

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As rovers get bigger and bigger, landing them gets tougher. That becomes the challenge for the engineers designing the Curiosity rover, the largest and most technologically advanced Mars rover ever built. Too big to land using the airbags that were successful on previous Mars rover missions, Curiosity calls for something new. So engineers come up with a novel system called the Sky Crane to lower the car-size rover to the Martian surface. While gasp-inducing with its system of rockets and a bungee-like umbilical cord, the Sky Crane precisely delivers Curiosity to the surface of the Red Planet before flying off to crash safely in the distance. The elegant touchdown, which allows for zero margin of error, is a seminal moment for the rover mission designed to investigate whether Mars has ever offered an environment favorable for microbial life.

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With the Nuclear Spectroscopic Telescope Array (NuSTAR), astronomers gain the ability to see sharp images of the high energy X-ray sky. NuSTAR's eyes can see through gas and dust to reveal black holes lurking in our Milky Way galaxy, as well as those hidden in the hearts of faraway galaxies. Among the first images from NuSTAR is a picture of Cygnus X-1, a black hole in our Milky Way that is siphoning gas off a giant-star companion. Finding these most elusive and energetic black holes helps scientists understand the structure of the universe.

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The twin spacecraft of NASA's GRAIL (Gravity Recovery and Interior Laboratory) mission go into orbit around the Moon on Dec. 31, 2011 and Jan. 1, 2012. 2011. GRAIL's mission is to study the internal structure and composition of the Moon in unprecedented detail by measuring and mapping variations in the Moon's gravitational field. The two spacecraft -- GRAIL A (Ebb) and GRAIL B (Flow) -- fly one behind the other, with the distance between them changing slightly as they fly over areas of greater and lesser gravity. They are built upon the successful GRACE mission at Earth, which used two satellites to map Earth's gravitational field. Eventually, GRAIL generates the highest-resolution gravity field map of any celestial body and reveals an abundance of features never before seen in detail (including tectonic structures, volcanic landforms and basin rings).

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The first Earth-size planets orbiting a sun-like star outside our solar system are discovered by Kepler, a spacecraft developed by JPL and later managed by NASA's Ames Research Center designed to study exoplanets. The planets announced in this discovery, called Kepler-20e and Kepler-20f, are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet's surface, but they are the smallest exoplanets ever confirmed around a star like our Sun. Scientists view the discovery as an important milestone in the ultimate search for planets like Earth.

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Astronomers studying observations taken by the Wide-field Infrared Survey Explorer, or WISE, mission discover the first known "Trojan" asteroid orbiting the Sun along with Earth. Trojans are asteroids that share an orbit with a planet near stable points in front of or behind the planet. Because they constantly lead or follow in the same orbit as the planet, they never can collide with it. In our solar system, Trojans also share orbits with Neptune, Mars and Jupiter. Two of Saturn's moons share orbits with Trojans. Scientists had predicted Earth should have Trojans, but they have been difficult to find because they are relatively small and appear near the Sun from Earth's point of view.

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Getting in and out of orbit around a planet takes a lot of energy. But the job is easier when you're talking about a smaller object, such as a protoplanet. Taking advantage of ion propulsion, the Dawn spacecraft slips into orbit around the giant asteroid Vesta as the first of two objects it will orbit in the main asteroid belt. After spending more than a year at Vesta, Dawn will continue on to orbit the dwarf planet Ceres.

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When the Cassini spacecraft trains its radar instrument on the north polar region on Saturn's largest moon Titan, scientists see dark, smooth-looking patches that provide the first definitive evidence of bodies of liquid on a world other than Earth. More than 75 of these seas and lakes appear in the images of Titan, ranging from 1.8 to 43 miles (3 to 70 kilometers) across. These lakes and seas are not filled with water, but liquid hydrocarbons such as methane and ethane.

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NASA's CloudSat satellite begins revealing never-before-seen 3-D details about clouds as it sends back its first pictures from orbit. Among those first images are a top-to-bottom slice of a warm storm front over the North Sea and clouds over Alaska. CloudSat data allow scientists to peer into the clouds and see their layered complexity, their ice and water composition, and production of rain and snowfall. These measurements improve our understanding of the role clouds play in Earth's complicated climate system. CloudSat provides profiles of clouds during hurricanes and thunderstorms so scientists can learn more about the origin and development of extreme weather events.

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A landing on a Utah desert marks the delivery to Earth of a sample of cometary material, the prime objective of the Stardust mission. The material is collected in 2004, when the spacecraft makes a close flyby of comet Wild-2 gathering cometary and interstellar dust in a substance called aerogel. Scientists say the samples indicate that some comets may contain materials ejected from the early Sun and may have formed very differently than previously thought.

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If you want to see inside a comet, what about blasting a hole in it? That is the premise of Deep Impact, which spends 172 days and 268 million miles traveling to comet Tempel 1, where it releases an impactor that hits the comet nucleus. The collision generates a brilliant flash of light even brighter than expected, as ice and dust debris is ejected from the fresh impact crater. After flying by Earth in 2006, Deep Impact goes on to study extrasolar planets and, in 2010, conducts a flyby of comet Hartley.

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Finding and studying planets orbiting other stars has been a gradual process, advancing incrementally as observational tools have progressed. In a major advance, the infrared Spitzer Space Telescope for the first time captures the light from two known planets orbiting stars other than our Sun. Previously, all confirmed extrasolar planets had been discovered indirectly, by detecting how exoplanets cause their parent stars to wobble slightly or by measuring changes in the star's brightness as planets move in front of it. In new studies, Spitzer directly observes the warm infrared glows of two previously detected "hot Jupiter" planets, designated HD 209458b and TrES-1. The achievement caps a nearly 10-year search by astronomers since exoplanets were first discovered.

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The magnetometer aboard NASA's robotic Cassini spacecraft discovers something—perhaps an atmosphere—is distorting Saturn's magnetic field around Enceladus, a small, icy moon of Saturn barely 300 miles (500 kilometers) in diameter. Follow-up investigation with Cassini reveals an unexpectedly active south pole—towering jets of icy spray and, under the moon's icy crust, a global liquid water ocean with salts, simple organic molecules, and likely hydrothermal vents. Enceladus turns out to be one of the most promising places in our solar system to search for present-day life beyond Earth.

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The interstellar stuff that provided the building blocks for the solar system billions of years ago was relatively homogenous – a simple cloud of interstellar gas, dust and ice. Yet the most striking feature of our solar system today is the great diversity among its planets, moons, asteroids and comets. How did that come to be? Answering that question becomes the goal of the Genesis mission, which sends a spacecraft to collect samples of the solar wind – particles that continuously stream outward from the Sun – and bring them to Earth for analysis. The sample return capsule's landing in Utah turns out harder than planned when its parachute doesn't open, yet many sample collectors are successfully recovered. Researchers spend years analyzing the samples, and in 2011 announce that they show the Sun and inner planets formed out of different basic materials.

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With a 96-minute burn of its main engines, Cassini becomes the first spacecraft to orbit the ringed planet Saturn, going on to execute numerous flybys of Saturn's scientifically rich moons. Cassini's observations at Saturn's moon Enceladus, for example, reveal an icy plume shooting from the moon's surface and inspire further investigations into the possibility that life could exist there. In 2005, Cassini delivers its European-built Huygens probe equipped with six instruments to the surface of Titan to study the giant haze-enshrouded moon. The Huygens investigations along with Cassini's flybys uncover methane lakes, hydrocarbon sand dunes and an internal liquid water-ammonia ocean on Titan.

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Launched on June 10, 2003, Spirit and Opportunity, two rovers capable of traveling farther than any before them, arrive at Mars three weeks apart in January 2004, beginning their planned 90-day investigations of Mars' climate and water history. Exploring on opposite sides of the planet, the robotic geologists equipped with cameras, a microscopic imager and other tools far outlast their life expectancy, journeying more than 25 miles (43 kilometers) combined, and discover signs of a once wet Mars. Opportunity, still roving today, also finds strong evidence that conditions on the Red Planet could have been suitable for sustaining microbial life.

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Launched in 2001, NASA's Mars Odyssey orbiter detects copious hydrogen just beneath much of the Martian surface, which scientists interpret as enough frozen water to fill Lake Michigan twice. The hydrogen abundance is mapped with Odyssey's Gamma Ray Spectrometer suite of instruments. This finding leads to a follow-up mission, NASA's Phoenix Mars Lander, which in 2008 confirms and analyzes frozen water scooped from beneath a few inches of soil. Odyssey goes on to set longevity records: In December 2010, it becomes the longest-active Mars mission and continues to set a new record every day since.

The twin satellites of the Gravity Recovery and Climate Experiment (GRACE) mission, precisely measure the effects of shifting water on Earth’s gravity field, and map the transfer of water within and among land masses, oceans and ice sheets. A partnership between NASA and the German Aerospace Center, GRACE measures Earth’s gravity field by tracking the separation between the two satellites with an accuracy of less than a few tenths of the width of a human hair. The mission improves scientists’ understanding of how oceans circulate, how water is stored on land and how glaciers change. Grace also lays the groundwork for NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission, which maps the moon’s gravitational field.

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During an 11-day journey aboard the space shuttle Endeavour, the Shuttle Radar Topography Mission sweeps Earth's surface with a specialized radar to capture the first detailed topographic maps of the planet from space. The digital images are later refined and combined to create the first-ever digital elevation map of Earth. Diverse industries benefit from the data, which offer a much more accurate and standardized view of Earth than anything before it.

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Deep Space 1 is launched as a technology demonstration under NASA's New Millennium program designed to flight-test new technologies. It is the first interplanetary spacecraft to use ion propulsion, gently thrusting as it flies toward its flyby target, the asteroid 9969 Braille. In an extended mission, Deep Space 1 flies by the comet Borrelly.

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Mars Pathfinder lands on the surface of Mars, carrying the first rover to another planet. The Mars Pathfinder mission, designed to demonstrate a low-cost method for delivering a set of science instruments to the Red Planet, is the first wheeled vehicle to be used on any other planet in the solar system and serves as the foundation for the Mars rovers of today. The mission is also notable as the first to use airbags to land on another planet. The lander, formally named the Carl Sagan Memorial Station, and the rover, named Sojourner, both outlive their design lives -- the lander by nearly three times and the rover by 12 times.

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After a five-year voyage, the Galileo spacecraft arrives at Jupiter.

Galileo is the first spacecraft to directly measure Jupiter's atmosphere with a descent probe, and conducts long-term observations of the Jovian system. After discoveries including evidence for the existence of a saltwater ocean beneath the Jovian moon Europa's icy surface, extensive volcanic processes on the moon Io and a magnetic field generated by the moon Ganymede, Galileo plunges into Jupiter's atmosphere on September 21, 2003 to prevent an unwanted impact with Europa.

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Magellan, a spacecraft with a sophisticated imaging radar that eventually makes the most highly detailed maps of Venus ever captured, is the first spacecraft to test a new maneuvering technique that uses the planet's atmosphere to slow or steer a spacecraft. This technique, known as aerobraking, makes the orbit around Venus more circular so Magellan can collect better gravity data. Flight controllers first attempt the maneuver on May 25, 1993 (after the mission's fourth mapping cycle of Venus) and dip Magellan into Venus's atmosphere on each orbit until Aug. 3, 1993. On Oct. 12, 1994, Magellan also becomes the first spacecraft intentionally crashed into a planet. Flight controllers chose this trajectory so that Magellan could gather valuable data on Venus's atmosphere.

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While its ultimate destination is Jupiter and its mysterious moons, the Galileo mission also becomes notable for discoveries during its journey to the gas giant. It is the first spacecraft to visit an asteroid, called Gaspra. Galileo also provides the only close observations of a comet colliding with a planet when it witnesses fragments of comet Shoemaker-Levy 9 impact Jupiter. And its flight past Venus in 1990 yields fascinating infrared images of the planet's clouds. Two years later, Galileo encounters a second asteroid, Ida, and discovers a miniature moonlet orbiting the rocky object, later given the name Dactyl.

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Ulysses is the first mission to survey the space environment above and below the poles of our Sun. A collaboration between NASA and the European Space Agency, Having used Jupiter’s gravity to reach its unique high inclination orbit, Ulysses studies the previously unexplored regions of the Sun's poles. Ulysses eventually completes three full orbits around the Sun and reveals for the first time the 3D character of galactic cosmic radiation, monitors solar wind variation from the poles between solar maximum and minimum, and discovers interstellar dust in the solar system.

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Twelve years after leaving Earth, Voyager 2 makes its closest approach to any planet since starting its journey, flying about 3,000 miles (4,950 kilometers) above the north pole of the planet Neptune. Voyager discovers that Neptune – the eighth and outermost planet from the Sun – has the strongest winds of any planet encountered, even though it receives the least solar energy. The spacecraft's flyby of Neptune sets it on a course below the elliptic plane that will eventually take it beyond the edge of the solar system.

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After flying by the planets Jupiter and Saturn, Voyager 2 makes history as it executes the first-ever encounter of Uranus, the seventh planet from the Sun. A gas giant, Uranus orbits the Sun 20 times the distance of Earth’s orbit. Resembling a pale blue billiard ball, Uranus is distinctive because its axis of rotation is tilted sideways. Uranus has a retinue of 27 moons, including 10 discovered during the Voyager flyby, as well as a complex system of dark rings.

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A joint mission with the Netherlands and the United Kingdom, the Infrared Astronomical Satellite, or IRAS, provides the first infrared look at the sky from space following its launch from California's Vandenberg Air Force Base. Over just 10 months, the space telescope detects about 500,000 infrared sources, doubling the number of cataloged astronomical sources with discoveries of new asteroids and comets, and thousands of variable stars and starburst galaxies, as well as the core of our galaxy, which has never been detected. It also images disks of dust around stars that may be planetary systems in early stages of formation. IRAS paves the way for later space-based infrared observatories such as the Spitzer Space Telescope.

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As the Voyager 1 spacecraft flies by the giant planet Jupiter, it captures a picture of an active volcanic eruption on Jupiter’s moon Io. This discovery is the most surprising finding from Voyager's flyby; volcanism on Io had never been detected from ground-based telescopes or by NASA's Pioneer 10 and 11 spacecraft that previously flew by Jupiter. The volcano throws solid material upward at speeds of about 1,200 miles per hour, reaching an altitude of 100 miles.

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Taking a leap beyond the weather satellites of the 1960s and 1970s, Seasat becomes the first satellite carrying sophisticated instruments dedicated to studying Earth's oceans. Seasat carries a suite of sensors to make measurements of sea surface height, temperature, vector wind, atmospheric water vapor content, as well as the roughness of the sea surface. These sensors lay the foundation for more optimized measurements developed in ensuing decades. The payload includes the first civilian imaging radar, an instrument used later to study Earth and other planets with great success.

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JPL's Viking 1 Orbiter launches carrying a NASA lander that will become the first lander to return scientific data. Viking 1 and its sister mission, Viking 2, are designed to investigate the Red Planet and search for signs of life. The Viking 1 and 2 orbiters take comprehensive high-resolution images of the planet during their missions.

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Mariner 10 is the first spacecraft to pass close to Mercury, a feat that will not be repeated for more than 30 years. Flying just 437 miles (703 kilometers) above the planet, Mariner 10 goes on to perform two more encounters of Mercury that enable it to map half the globe. It also reveals a surprising magnetic field and a metallic core comprising about 80 percent of Mercury's mass. Mariner 10 was also the first interplanetary spacecraft to use a "gravity assist" maneuver in February 1974 where it used the gravity of Venus to bend its flight path toward Mercury.

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Mariner 10 becomes the first spacecraft to conduct multiple planet flybys as it executes encounters of Venus (2/5/74) and three passes by Mercury (3/29/74, 9/21/74 and 3/16/75). This is the first demonstration of the technique of “gravity assist,” using the gravitational pull of the target planet to bend and shape the spacecraft's flight path. At Venus, Mariner 10 produces the first clear pictures of the Venusian chevron clouds and performs other atmospheric studies.

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Mariner 9's arrival at Mars makes it the first spacecraft to orbit another planet, narrowly beating the Soviet Union's Mars 2, which reaches the Red Planet two weeks later. Mariner 9 is also the first spacecraft to make close observations of Mars' two moons, Phobos and Deimos. While in orbit, Mariner 9 maps 85 percent of the Martian surface, and collects valuable information about Mars' surface and atmosphere. Of the more than 7,000 images it transmits, some of the most significant are the first detailed views of the solar system's largest volcano and a canyon system that dwarfs the Grand Canyon.

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The first of the Surveyor missions designed to make soft landings on the Moon, Surveyor 1 provides information about Earth's natural satellite that will be critical for the Apollo crewed missions. Surveyor 1 sends home 11,240 high-resolution television pictures, as well as data on the Moon's bearing strength, temperatures and radar reflectivity. The soft landing is achieved using a retrorocket and a bank of three thrusters that slow the lander's speed from almost 6,000 miles per hour to just 3 miles per hour.

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After an eight-month voyage, Mariner 4 performs the first flyby of Mars, becoming the first spacecraft to take close-up photographs of another planet. The images show lunar-type impact craters, some of them touched with frost in the chill Martian evening – a disappointment to many who had hoped for a more habitable-looking environment on the Red Planet. A television camera takes 22 pictures, and radio science data provides key information about how to safely deliver future missions to the Martian surface. After passing Mars, Mariner 4 lasted about three years in solar orbit, continuing long-term studies of the solar wind and making coordinated measurements with the Mariner 5 spacecraft.

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The Ranger 7 lunar probe is the first unqualified success in the United States' early quest to explore the Moon, and heralds a new era of exploration that sees dramatically more mission successes than failures. Designed chiefly to take high-resolution photographs of the Moon as it descends to make an intentional crash-landing, Ranger 7 approaches the Moon precisely on target and captures more than 4,300 images as it drops toward a region later named Mare Cognitum. Ranger 7 returns images of the Moon from distances as close as 2,110 km – vastly closer than pictures from any previous Soviet or U.S. spacecraft.

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To receive signals from and plot the orbit of Explorer 1, JPL had, under contract with the U.S. Army, deployed portable tracking stations to Nigeria, Singapore and California. After JPL is transferred to NASA, the agency recognizes the need for a more extensive communications network rather than having each flight project acquire and operate its own equipment. JPL's Deep Space Information Facility is renamed the Deep Space Network on December 24, 1963, to reflect the expanded role, becoming the "phone company" for nearly every spacecraft that has gone to the Moon or beyond.

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One hundred nine days after launch, Mariner 2 flies by Venus, becoming the first spacecraft to execute a successful encounter of another planet. It passes about 21,600 miles (34,773 kilometers) above the surface and scans the planet with infrared and microwave radiometers, revealing that Venus has an extremely hot surface. This supports a theory put forward by some scientists that Venus is the victim of a runaway "greenhouse effect"; carbon dioxide in its atmosphere acts like a blanket, trapping heat from the Sun. The finding puts to rest longstanding speculation that the cloud-shrouded Venus might be a swampy world harboring life.

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Pioneer 4 is the second of two early attempts by the United States to send a spacecraft to the Moon. The spacecraft achieves its primary objective -- to put itself on a trajectory from the Earth to the Moon -- and is the first American mission to escape Earth orbit. While it flies farther away from the Moon than expected and does not take the images of the Moon its designers intended, Pioneer 4 does provide extensive and valuable data on Earth’s radiation belt and the tracking of space objects. After 82 hours of transmissions from Pioneer 4's tiny radio and 655,000 miles (1.05 million kilometers) of travel -- the farthest tracking distance for a human-made object at the time -- contact is lost on March 6, 1959. Pioneer 4 is still in orbit around the Sun.

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Two months after the National Aeronautics and Space Administration is created by Congress, JPL is transferred from U.S. Army jurisdiction to that of the new civilian space agency. It brings the new agency experience in building and flying spacecraft, an extensive background in solid and liquid rocket propulsion systems, guidance, control, systems integration, broad testing capability and expertise in telecommunications. JPL takes on the responsibility of planning and executing lunar and planetary missions, and developing the rocket and upper stages needed to launch spacecraft to the Moon and the planets.

With the launch of Sputnik, the first satellite to orbit Earth, on October 4, 1957, by the Soviet Union, Cold War America is eager to send its own satellite into orbit. JPL's work for the U.S. Army makes it possible to develop the flight, ground systems and hardware necessary to fly the first successful U.S. space mission, Explorer 1, a few months later. Even this first spacecraft makes an important scientific discovery: radiation belts around Earth held in place by the planet's magnetic field. These belts are named after James Van Allen, the scientist who designed the main instrument on Explorer 1. This project marks JPL's shift in emphasis from rockets to what sits on top of them.

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JPL embarks on a project with the U.S. Army Ballistic Missile Agency to see if warheads on the top of missiles can be returned safely from space. The ABMA/JPL team conducts three successful suborbital flights. Equipment developed in this program serves as the basis for Explorer 1, the United States' first orbiting satellite, in January 1958. It also lays the groundwork for heatshields to return astronauts to Earth and to help rovers land on Mars.

In mid-1944, JPL embarks on a program called "Corporal," to develop a guided ballistic missile. The first rocket in the program is known as the "WAC Corporal." It is a 16-foot-long (5-meter-long) missile designed for upper atmosphere research and later evolves into the Aerobee sounding rocket, which is used frequently in the 1950s for this scientific purpose. While the WAC Corporal is a rapid success, the full-scale Corporal proves to be more difficult. The second Corporal test flight becomes known as the "rabbit killer" for an unexpected horizontal flight. Several battalions of Corporal missiles are deployed to Europe in the 1950s under the military designation MGM-5.

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Building on their "jet-assisted take-off" rockets for the U.S. Army, the Caltech group develops an 8-foot-long (2-meter-long), fin-stabilized rocket called the Private A. On its first test flight on Dec. 1, 1944, it achieves a range of 11 miles and proves the feasibility of this kind of ballistic missile. They experiment with radio telemetry from missiles, and begin planning for ground radar and radio sets to monitor performance.

Theodore von Kármán and his Caltech research team propose to the U.S. Army Air Corps a research project to understand, duplicate and reach beyond the German rocket program. In the proposal, the team refers to their organization for the first time as "the Jet Propulsion Laboratory."

With World War II looming, the U.S. Army Air Corps sees value in the rocket experiments conducted by Caltech's Guggenheim Aeronautical Laboratory and becomes the lab's first patron. The first project commissioned is to develop "jet-assisted take-off" rockets, which help heavy bombers take off from short runways.

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Theodore von Kármán, the head of the Guggenheim Aeronautical Laboratory at Caltech, is overseeing pioneering work on rocket propulsion when a pair of young rocket enthusiasts, John W. Parsons and Edward S. Forman, come to him looking for help. Von Kármán connects them to some grad students, and on Halloween, a group goes out to the Arroyo Seco, a dry canyon wash at the foot of the San Gabriel Mountains on the northwest edge of Pasadena. The seven men -- Frank Malina, A.O. Smith, William Bollay, Carlos Wood, William Rockefeller, Parsons and Forman -- try four times to ignite a small rocket motor to gather thrust data, with only the last attempt succeeding (and setting fire to the outside of the motor, too).

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