Since the launch of Sputnik 1 in 1957, humans have been putting more and more elaborate and technically sophisticated probes and satellites into space. The last thirty years has seen tremendous developments in terms of the technology used in space exploration—solid fuels, solar panels, and radioactive power sources are just some of the remarkable innovations that have allowed space agencies across the planet to tackle evermore ambitious missions that would once have never been thought possible. So now that we’ve explored most of our solar system with fearless, pioneering space robots, it’s time to pick out which ones are our favorites.
10. Deep Impact
Like Rosetta-Philae, Deep Impact was another spacecraft sent to gather information about speeding comets. However, rather than attempting to land on one, Deep Impact’s mission was to smash an “impactor” into the comet Tempel 1. Why, you might ask? Well, scientists pretty much just wanted to see what would happen. Prior to this mission they had never had a firm grasp on what the physical composition of a comet was like. Deep Impact was the first experiment to probe beneath the surface of a comet. The instruments onboard the spacecraft, along with ground-based telescopes and space-based observatories, recorded the impact and examined the resulting debris and interior material. The mission has greatly advanced our understanding of comets and provided a wealth of data that will take years to fully interpret.
Sent on a mission to study Jupiter and its surrounding objects, Galileo is an orbiter/probe combo that was launched in 1989 aboard the space shuttle Atlantis. After gaining speed though a gravitational assist flyby of Venus and Earth, Galileo arrived at Jupiter in 1995 and became the first spacecraft to orbit the gas giant. The wealth of data gathered since then has given us information about Jupiter’s immense gravitational field, its cloudy ammonia-rich atmosphere, and hinted at evidence of liquid water beneath the icy crust of its moons Europa, Ganymede, and Callisto. But Galileo’s achievements don’t stop there; it was also the first spacecraft to do an asteroid flyby and the first to discover an asteroid moon.
8. New Horizons
Scientists have been trying to send a probe to Pluto for years, but due to underwhelming support from NASA and increasing costs, many projects were scrapped before they could ever get off the ground. Luckily, all hope was not lost. In 2006, NASA launched New Horizons on a mission to explore Pluto, its moons, and the Kuiper belt. A good portion of New Horizons’ lengthy voyage was spent in hibernation in order to conserve power, however, it was periodically awakened to check its systems and scientific capabilities. When the probe finally arrived at Pluto in July 2015, it began mapping the planet and gathering data on its moon. As it continues its study in the years to come, New Horizons will look for signs that indicate the presence of an atmosphere, planetary rings, and much more.
Named after the astronomers Giovanni Cassini and and Christiaan Huygens, this two-part spacecraft was launched in 1997 on a mission to study the planet Saturn. Cassini is an orbiter designed to zoom around Saturn and take pictures of its rings and moons, while Huygens—the probe component—was sent down to the surface of the planet’s moon, Titan. Since the spacecraft arrived at Saturn in 2004, both missions have been hugely successful with Cassini sending back stunning images, and Huygens plunging through Titan’s cloudy atmosphere to reveal an ultra-cold environment rich with liquid methane and solidified rocks made from water.
6. Viking 1
Launched in 1975, NASA’s two-part Viking program was the first to land on Mars and successfully carry out its mission by capturing surface images of the red planet. In fact, Viking 1 held the record for longest Mars surface mission (2307 days) all the way up until 2010, when the record was broken by the Opportunity Rover. Although some might argue that the Soviet-built Mars 3 was the first to land on Mars, since that mission was ill-fated—resulting in the lander becoming inoperative only seconds after touchdown—Viking 1 gets the glory.
MErcury Surface, Space ENvironment, GEochemistry, and Ranging is the backronym commonly used to describe the MESSENGER probe. It was launched in 2004 aboard a Delta II rocket and, after arriving at Mercury in 2011, orbited the planet for four years, gathering data about magnetic field patterns, chemical composition, and geology. Some of the images and sensor data collected from MESSENGER suggested that Mercury contains an abundance of water trapped within its shadow-covered polar craters. This archaic ice, covered in a thick layer of dust and organic compounds, adds weight to a theory that some astronomers think points to the mechanism by which the inner solar system attained its water. The water on Mercury supports a hypothesis proposing that the inner planets were bombarded with icy asteroids and comets in the early stages of the solar system’s formation. Furthermore, these types of icy bodies might very well contain the types of organic compounds that make up the building blocks of life as we know it on Earth.
4. Mars Reconnaissance Orbiter (MRO)
In order to pave the way for other surface missions to Mars, it helps to have detailed information about things like landforms and planetary weather patterns. That’s why NASA launched the Mars Reconnaissance Orbiter (MRO) in 2005. The multipurpose spacecraft was equipped with a range of scientific instruments such as cameras, spectrometers, radar, and an elaborate telecommunications system that it uses to locate potential landing sights and send the information back to Earth. The MRO has been such a success that its mission has already been extended well past its original end date of 2010, and is predicted to transfer more data back to Earth than all previous interplanetary missions combined.
MESSENGER might have been the first probe to show us that comets can bring water to inner planets, but it was Rosetta-Philae that gave us our first close-up look at the surface of a comet. In 2004, the spacecraft was launched on a mission to rendezvous with Comet 67P/Churyumov–Gerasimenko, so that it might tell us more about these frozen rocks that periodically plunge into our solar system and whip around our sun in startling elliptical orbits. After a 10 year journey that included many gravity assists from Earth and Mars, the space probe finally reached the target comet in late 2014 and performed the first successful landing on a comet’s surface. Philae immediately began analyzing the surface composition as the comet began to melt and erupt superheated gas as it grew closer to the sun. The plumes of heated gasses created by melting are transformed into the comet’s tail as it speeds through space. The images and analysis conducted by Rosetta have shown that water molecules break up slightly differently on the comet than they do on Earth.
The Mars rovers have shown to be some of the best space explorers ever created, and none more so than Curiosity. It was launched on November 26, 2011, from Cape Canaveral and, after deploying a technically mind-blowing parachute/sky crane landing procedure, it touched down on the red planet on August 6, 2012. Curiosity has been tasked with accomplishing a number of goals aimed to extend our knowledge of nature; some of them include investigating the Martian climate and geology, assessing whether the planet has ever maintained environmental conditions favorable for microbial life, and performing habitability studies in preparation for future human expeditions to the planet. Even though it has only travelled as far as the surface of Mars, the sheer volume of data that Curiosity has gathered and sent back to Earth is staggering and it’s currently our best chance at finding other traces of life in our solar system.
1. Voyager 1
Voyager 1 made a return to the center stage of space exploration in 2012, when it became the first spacecraft to leave our solar system and journey out into deep space. The probe has been operational for nearly 40 years and, after completing its primary mission surveying the planets Jupiter and Saturn, picked up enough speed to go beyond the safe envelope of our sun’s protective magnetic heliopause. Scientists had always hoped the Voyager probes would accomplish this and, in preparation, loaded each of the spacecraft with a golden record containing various sounds and messages from Earth. Although the technology seems horribly outdated by today’s media standards, these famous gold records are our cosmic “message in a bottle” and could one day give an alien civilization a tiny glimmer of our existence.