Milena Niemczyk — 1st Nicolaus Copernicus Secondary School, Bielsko-Biata, Poland
Introduction
Our eyes have always been directed towards the night sky. The inventions of the telescope and then spacecraft have since augmented our pursuit of celestial knowledge. Beginning with the success of the Mariner 2 mission to Venus, the American probe that was the first to visit a planet other than Earth, it became feasible to directly visit celestial bodies rather than just study them with telescopes located on our planet. Then, ground-based observations of the night sky ceased to be the end of our research, but the beginning of active research into the Solar System. So, what were the most interesting missions of exploration within the Solar System? You will find out in this article, so I invite you to a journey with the best guides in the universe – space probes.
Parker Solar Probe
We will start our tour with the object that absolutely dominates our region of space – the Sun. In 2018, one of the most difficult and ambitious missions in the entire history of space exploration was launched in its direction. This is the Parker Solar Probe, which is often referred to as the ship that “touched the Sun” because during some flybys of our star, the spacecraft came within 6.1 million kilometers of our star’s surface, causing it to pass directly through the Sun’s corona — the outermost part of the Sun’s atmosphere. For comparison, if the distance between the Sun and the Earth were to be one meter, then the probe would be only 4 cm (1.6 in) from our day star. This was made possible by seven gravity assists near Venus[1]. The ship also reaches enormous speeds, reaching up to 680,000 km/h! This makes it the fastest object ever built by humans. All of these successes were preceded by decades of developing complex technology. Temperatures so close to the Sun can be as high as 1,400 degrees Celsius, so how does the probe cope with this? On the front of the ship’s hull there is a special heat shield, covered with white paint that reflects sunlight. All four scientific instruments are therefore “hidden” behind the shield and can operate at a pleasant temperature of about 30 degrees Celsius.
The probe’s mission will end this year, but it has already discovered magnetic switchbacks, which are disturbances in the movement of the solar wind, and discovered twenty comets. The Parker Solar Probe continues to study the Sun, focusing on the solar corona and solar wind, but in addition to this, one of the key aspects of the mission is also to better understand the environment between the Earth and the Sun. This environment is dominated by the solar wind which buffets the Earth daily. Particles from the solar wind were collected by another NASA probe – Genesis – and then delivered to Earth in 2004, although they were only partially recovered by the failure of the capsule’s parachutes. By contrast, the Parker Solar Probe can study solar wind particles very close to their source.
Parker Solar Probe
(By NASA/Johns Hopkins APL/Steve Gribben)
Mars 2020
We move away from the Sun and move to the red planet – Mars. An object of interest for many space agencies, and the future goal of establishing a human base on its surface. To do this, orbiters, rovers and even a helicopter have been sent to the planet over several decades for research. The last mission sent there is the American Mars 2020. This mission included the Perseverance rover, as well as the small helicopter Ingenuity. The spacecraft landed on the planet’s surface in February 2021 in the Jezero crater, where a body of water was located several billion years ago. The rover resembles its predecessor, the Curiosity rover – the fourth NASA vehicle to drive on the surface of this planet. The ongoing Perseverance mission is intended to bring us closer to future human exploration on this planet – for this purpose, the rover has already collected several samples of Martian soil, which are to be delivered to Earth as part of the Mars Sample Return mission. The rover also performed the MOXIE experiment, which involved producing a few grams of oxygen from carbon dioxide in the Martian atmosphere. In the future, such oxygen could be used as a component of rocket fuel or as a breathing gas for astronauts. In addition to the seven main scientific instruments, the rover includes chips with the names of 10 million people from around the world and a tribute to health care workers. Besides studying the planet’s geology, the rover discovered the presence of organic compounds.
The Mars 2020 mission also had another interesting element – the first powered flying spacecraft. For the first time, engineers attempted to fly a machine in a controlled way in the atmosphere of another planet[2]. This was achieved by the Ingenuity miniature helicopter in April 2021, when it rose 3 meters above the surface and flew for 40 seconds in the thin Martian atmosphere. The engineers planned a maximum of several flights; one was already a huge success and finally… the helicopter made as many as 72 of them! Altogether, it flew a total of about 17 kilometers over about 128 minutes. Interestingly, the helicopter carries part of the wing of the Wright brothers’ plane – the first airplane to fly in the Earth’s atmosphere. The astronauts of the Apollo 11 mission had a similar piece with them during the first human landing on the Moon. The Ingenuity mission has opened the gate for more missions of autonomous flight on alien worlds. In the future, a larger helicopter will be sent to Mars, and even later a Dragonfly helicopter will be deployed on Saturn’s largest moon – Titan.
Ingenuity during first flight in the Mars atmosphere (By NASA/JPL-Caltech)
Comets and Asteroids
The Solar System consists not only of planets, but also thousands of smaller celestial bodies. Let’s start with comets. They have been observed since antiquity, and it was then that the eerie appearance of a comet in the night sky heralded misfortune. Today, we know quite a lot about them from telescopic studies and robotic flybys. We even managed to land on the rocky and icy surface of one comet’s nucleus in 2014! Specifically, we are talking about the European Rosetta/Philae mission, which targeted comet 69P/Churyumov-Gerasimenko.
After a 10-year journey to the comet, the Rosetta orbiter observed the comet for over two years and made many surprising discoveries. It turned out that the structure of comets resembles a sponge inside, and when gases from its surface interact with the solar wind – a phenomenon similar to the auroras that we see on Earth is created! A significant difference in the composition of water (in the form of ice) on the comet was discovered in relation to water from Earth’s oceans, which prompts further research on the origin of this precious chemical compound here on Earth. As on Mars, many organic compounds have been found. The orbiter also carried the Philae lander which landed on the surface of the comet – although not without problems. Philae bounced twice and landed the third time. The lander settled in a disadvantageous position, which hindered communication, but it did most of the planned work and activated all ten scientific instruments. It is worth mentioning that before the Rosetta probe, samples of material from comet Wild 2 had been delivered to Earth by the Stardust probe in 2006, and even the impactor of the Deep Impact mission was driven into the nucleus of comet Tempel 1 a year earlier.
When it comes to asteroids, we often think of them as objects that are the cause of a great catastrophe, as was the case with the extinction of the dinosaurs 65 million years ago. To avoid the fate of these reptiles, a planetary defense program was launched. As part of it, in 2022, the American DART probe deliberately hit the surface of the asteroid Dimorphos to change its trajectory around the larger asteroid Didymos, which was successful. Four years after the impact, the European Hera probe will go for detailed observations there. Despite the general fear associated with these celestial bodies, it is possible to make use of them – we are talking about space mining, which would involve obtaining valuable raw materials that are found on Earth in very small quantities (or none at all) from asteroids. The American company AstroForge is the first to plan such operations – unfortunately, none of their test missions so far have been successful. The best candidates for obtaining raw materials are metallic asteroids, i.e. those that consist of iron or nickel. The largest of its kind is the asteroid (16) Psyche, which NASA’s probe of the same name is heading to – it is scheduled to reach the asteroid four years from now.
Despite the still distant vision of space mining, we have witnessed the delivery of samples of material from asteroids to our planet by three separate space probes. In 2005, the Japanese Hayabusa probe landed on the surface of the asteroid Itokawa, which five years later delivered the collected samples to Earth. Its success was repeated by the Hayabusa 2 mission, which visited the asteroid Ryugu, re-collected the necessary material and explored the surface of the asteroid with two small rovers. Also, the American OSIRIS-REx mission in 2020 collected about 100 g of samples from the asteroid Bennu and delivered them to Earth. In January 2025, the discovery of many organic compounds in samples from this asteroid was announced – we are talking about many amino acids, the building blocks of proteins, as well as nucleobases, the building blocks of DNA and RNA.
We have also sometimes confused asteroids with… space probes. During one of Rosetta’s flybys of Earth, astronomers identified the spacecraft as a 20-metre asteroid – which was quickly cancelled and clarified. A similar situation occurred earlier this year, when the Tesla Roadster, the test payload of the first flight of the Falcon Heavy rocket, was recognized as a potentially dangerous object for our planet, which was again quickly denied.
Jupiter and Saturn
It’s time to move to the vicinity of the two largest planets in the Solar System. We will start with the king of the planets, i.e. Jupiter. The first probe to orbit this planet was the Galileo probe. The mission, named after the Italian astronomer Galileo, who discovered the planet’s four largest moons, launched aboard the space shuttle Atlantis in 1989. On its way to Jupiter, the spacecraft became the first spacecraft in history to visit the asteroid Gaspra. Once near the planet, it observed the impact of comet Shoemaker-Levy 9 into Jupiter’s atmosphere. Galileo orbited Jupiter more than 34 times and explored all the largest moons (Ganymede, Callisto, Io, Europa) that can be observed from Earth even with binoculars as points around the planet. The probe discovered that under the surface of one of these moons – Europa – there is an ocean of liquid water (this is the direction towards which the new probe, the Europa Clipper is currently heading, which will study this moon). We also learned that Ganymede has its own magnetic field. Galileo’s study of the volcanoes on Io outpaced the collective studies of them from Earth. The conditions currently prevailing on this celestial body may resemble our planet during its formation billions of years ago. In addition to studying the moons, a probe was released into Jupiter’s atmosphere, transmitting data for almost an hour and flying about 200 km in the planet’s dense clouds. Galileo, after more than three extensions of the mission, burned up in the planet’s atmosphere in 2003, freeing up space for other probes – Juno, which is still studying the planet and flew over its poles, JUICE – which will aim to explore three of the four largest moons, and the aforementioned Europa Clipper mission. These new probes should bring us closer to answering the question: Is there, or has there ever been, life on Europa?
Flying farther from the Sun, we will encounter another planet – Saturn. Known primarily for its majestic rings, the planet welcomed its first orbiter only in 2004 with the Cassini-Huygens mission, a joint project of NASA and ESA[3]. Over nearly 300 orbits around the planet, the orbiter studied the structure of the planet, flew through the planet’s rings, and studied natural satellites. The probe discovered that one of the moons, Enceladus, has ice geysers, proving that there is an ocean of liquid water beneath its surface. Besides the Cassini orbiter’s extensive study of the Saturnian system, the landing of Huygens on the surface of Titan has led to many exciting discoveries. Interestingly, very little was known about the conditions on the surface of the moon during the planning of the spacecraft, so engineers designed the vehicle so that it could land on any surface – solid or liquid. In the end, the ground resembled wet sand. We now know that on the second largest moon in the Solar System, there are rivers or seas filled with liquid methane and ethane, and deeper below the surface there is an ocean filled with water. Its atmosphere is composed mainly of nitrogen, making the moon another potential place (along with Enceladus) to look for life beyond our planet in the Saturn system. After a twice-extended mission, Cassini, like Galileo, burned up in the planet’s atmosphere during the final phase of the mission, dubbed the Grand Finale in 2017. Why are space probes simply not left in the orbits of planets? That is to avoid the collision of the spacecraft with interesting moons of the planets in the future, thus leaving them in their natural state without terrestrial contamination.
Pioneers and Voyagers
Approaching the end of our interplanetary journey, it is impossible to ignore the probes that have left our planetary system forever. These are the Pioneer 10 and 11 probes, launched in 1972 and 1973 respectively, and the more famous Voyager 1 and Voyager 2 probes, of which the second probe was launched a month earlier than the second. The first mission, Pioneer 10, was a huge success – it was the first to fly (unscathed!) through the asteroid belt and was the first mission to visit Jupiter. The twin spacecraft Pioneer 11 flew over the poles of the largest planet for the first time and visited Saturn for the first time. It discovered a new moon and another ring around the planet. Both spacecraft, after investigating their targets, began to leave the Solar System. Pioneer 10 is heading towards the star Aldebaran in the constellation of Taurus, while Pioneer 11 will pass the star Lambda Aquilae in the constellation of the Eagle in about four million years – both ships are currently moving at a speed of about 12 km/s. On board the probes, plates with the image of a woman and a man and with information about the origin of the ship were placed.
Four years after the launch of the Pioneer 11 probe, two probes of the Voyager program went into space. Voyager 1 provided a lot of information about Jupiter and Saturn and was the first to officially leave the Solar System in 2012 and to this day remains the most distant man-made object (at the time of writing, it is about 25 billion kilometers from Earth). It was this probe that in 1990 took a photo of the Earth called “Pale Blue Dot” from a distance of about 6.4 billion kilometers from our planet, which shows that we are only a blue grain amidst the darkness of space, illuminated by the Sun. Voyager 2, on the other hand, visited all the gas giants, including Uranus and Neptune for the first time. The next favorable alignment of the outer planets will not take place until more than a hundred years later! The probe discovered 11 new moons of Uranus and six new moons of Neptune. In addition, it observed for the first time a ring system on the last planet of the Solar System. On board both probes, there are Golden Plates (Voyager Golden Records), which are carriers of data about us – the inhabitants of planet Earth, our culture, languages, and the nature around us. The fifth mission to leave the Solar System is the New Horizons spacecraft, which has studied Pluto and the Kuiper belt object Arrokoth (it resembles a snowman in shape), which is the most distant celestial body ever visited by a space probe.
Voyager Golden Record (By NASA/JPL)
Notes
[1] Gravity assist is a maneuver that allows a spacecraft to change its direction of flight or speed (by braking or accelerating) through a planet’s gravitational field. The first mission to use this maneuver is the American Mariner 10 probe – the first spacecraft to visit Mercury.
[2] The Ingenuity flight is the first controlled flight, the Vega 1 and Vega 2 research balloon flights in the atmosphere of Venus in 1985 were uncontrolled flights.
[3] ESA – European Space Agency
Much of this report is based on:
https://en.wikipedia.org/wiki/List_of_Solar_System_probes#,
NASA and ESA online pages, and the Polish book Beyond Earth…The History of Interplanetary Flight by Krzysztof Ziołkowski
Milena Niemczyk wrote this report as a freshman student at the 1st Nicolaus Copernicus Secondary School in Bielsko-Biala, Poland. She cited her physical education teacher, Rafal Widuch as her reference.