October 4 marks the 67th anniversary since the launch of the Earth’s first artificial satellite. This date is considered to be the beginning of the space era worldwide.
When we talk of artificial satellites, we tend to refer to those specifically orbiting Earth, which is only fair, considering that they comprise over 99% of all spacecraft. That said, artificial satellites designed for orbiting other bodies of the Solar system do, in fact, exist. In commemoration of the 67th anniversary since the launch of the first satellite, let’s dive into their history in more detail.
Why There Are So Few Interplanetary Satellites
The short answer to the question of why there are so few interplanetary satellites is also a simple one. Their design and manufacturing are not only complex, but also exceptionally costly.
One of the main reasons for this complexity is the speed. In order to reach low earth orbit, objects have to accelerate to the first cosmic velocity of 8 km/s or roughly 5 miles per second. But interplanetary objects will have to do better than that and reach the second space velocity — 11.2 km/s or approximately 7 miles per second — also knows as the escape velocity. This, in turn, requires the use of more powerful rockets.
But accelerating a spacecraft wouldn’t be enough. Both its speed and trajectory need to be precisely calculated so that, at a specific point, the craft could use the planet’s gravity to enter the circular orbit. If the speed is too high, the spacecraft will simply escape the orbit and fly into space. If the speed is too low, it won’t be able to reach its destination at all.
Satellites orbiting other planets also require more powerful communications systems compared to what Earth satellites use for data transmissions.
Additionally, each planet presents its own set of challenges that need to be taken into consideration during the spacecraft design stage. For instance, satellites of inner planets require advanced shielding from solar radiation, while Jupiter-bound satellites must be equipped with additional armor to protect their control systems from cosmic rays. As for the outer Solar System, the problem flips on its head: those distant corners don’t get enough sunlight, and satellites can’t rely on standard solar panels. So the only way around it is to power the spacecraft with radioisotope thermoelectric generators.
While all these complications are perfectly solvable, they also shoot the cost of interplanetary missions through the roof. Hence why the majority of the programs that build and launch artificial satellites to other planets are the prerogative of government agencies. So far, private spacecraft haven’t ventured beyond the Moon.
Artificial Planetary Satellites
Aside from Earth, we have launched artificial satellites to five other planets in the Solar System: Mercury, Venus, Mars, Jupiter, and Saturn.
But this covers all of our space exploration history. As of 2024, only two planets still have man-made satellites. The first is, of course, Mars, with seven such spacecraft circling its orbit. Three of those belong to NASA (MRO, Mars Odyssey, MAVEN), two are from ESA (Mars Express and TGO), one is Chinese (Tianwen-1) and one from the UAE (Al-Amal).
This impressive fleet has reaped a truly bountiful harvest of data from the red planet’s atmosphere and surface. Their findings indicate that Mars once had a more sustainable climate and liquid water on its surface. Artificial Martian satellites play another important part — that of communication. They act as relay stations, transmitting data collected by Mars rovers to Earth.
The second planet is Jupiter, currently housing only one man-made satellite — Juno — that entered the gas giant’s orbit in 2016. The spacecraft’s main goal is to study Jupiter’s internal structure and atmosphere. In recent years, Juno also completed a series of flyby’s of Jupiter’s largest natural satellites, collecting troves of new data.
The number of artificial satellites, including spacecraft designed for inner planets, will increase in the upcoming years. In November 2026, the joint European-Japanese mission BepiColombo is scheduled to launch for Mercury’s orbit. Venus will also gain new companions — several programs are currently in development, with the plan to launch by the end of this decade.
Mars will also continue to receive new guests, starting with the two EscaPADE spacecraft in 2025 and followed by the Japanese mission MMX in 2026. The latter will focus on collecting samples from Phobos. China is planning their Tianwen-3 mission for 2028-2030, which will obtain Martian soil samples.
The next decade will kick off with the launch of two new Jupiter satellites — ESA’s JUICE probe and NASA’s Europe Clipper. The pair will focus on Jupiter’s natural satellites, studying the enormous oceans hidden beneath their icy surfaces.
Artificial Lunar Satellites
Countries with emerging space programs tend to focus their first missions on the Moon due to our satellite’s proximity. It comes as no surprise that, apart from Earth, the Moon is not only the most studied body in our Solar System, but also boasts the largest number of man-made satellites.
Currently, the Moon’s orbit is host to a number of spacecraft, from the experimental CubeSat CAPSTONE to such respected veterans as LRO. At the time of its launch, it carried the most powerful lunar satellite camera in history. This allowed LRO to map the Moon’s surface in incredible detail and capture all the Apollo landings as well as those of autonomous stations.
Then there’s the Indian Chandrayaan-2 launched in 2019 and South Korean Danuri that set sail in 2022, both now studying the lunar surface. And of course, Chinese relay satellites remain crucial for maintaining communication links with the missions located on the other side of the Moon or the lunar South Pole.
Not to be outdone by planets, the Moon will soon acquire its own slew of new man-made guests. Both the US and China will send additional satellites to collect data for upcoming lunar programs, though countries with newly developed space programs will be sending their own missions as well. Moreover, the Moon’s orbit will become a home to Gateway, the first ever station to orbit another celestial body.
Artificial Satellites of Comets and Asteroids
Planets are not the only ones to be graced with man-made satellites. Small celestial bodies have had their fair share over the years, namely the dwarf planet Ceres, asteroids Eros, Vesta, Bennu, Ryugu and Itokawa, as well as comet Churyumov-Gerasimenko.
It should be noted, however, that the smallest asteroids out there lack the necessary gravitational pull to hold onto satellites. So to say that satellites orbit them would be inaccurate. Rather, the spacecraft matches the asteroid’s heliocentric orbit, and then it’s up to the engineers to take the wheel and guide them.
Either way, as of 2024, small Solar System bodies have no artificial satellites. But this is soon to change. In December 2026, ESA’s Hera spacecraft will visit the binary asteroid system Dimorphos-Didymos. Two years prior, NASA crashed its DART probe into Dimorphos to see if they could alter its orbit. Now it’s Hera’s turn to snoop. Its mission is to examine the effects of the impact on the system’s orbit and find the crater itself.
In 2026, one of Earth’s quasi-satellites, Kamoʻoalewa, will get its own artificial companion with the upcoming Tianwen-2 from China. The spacecraft will study it from orbit, then collect soil samples and send them back to Earth.
One of the most intriguing objects in the Main Asteroid Belt, Psyche, will also be receiving a visitor. Psyche’s surface is brimming with various metals, and it’s believed that the asteroid could be a leftover fragment of a late protoplanet. At least, this is what mission Psyche will attempt to find out upon its scheduled arrival in the asteroid’s orbit in summer 2029.
Of course, we have to mention Apophis. In 2029, this asteroid is predicted to fly by Earth at a distance of only 32,000 km — roughly 20,000 miles. Such a rare event has astronomers buzzing with excitement: ESA is planning to launch its spacecraft Ramses, while NASA has already sent its probe OSIRIS-APEX. Previously named OSIRIS-REx, the probe spent two years studying asteroid Brennu and collecting the asteroid’s soil samples. Now, it will become a satellite of another small Solar System body.