The Most Distant Planetary Probes to leave Earth

Humans have pushed the frontiers of exploration in space by sending probes to the edge of our Solar System and beyond. Just how far have we traveled, and what have we seen along the way? How do we keep in touch with the most distant objects, and what is left to learn from these probes? 

In the June 2025 episode of the Translunar Podcast, I discuss the very old Pioneer and Voyager missions past Jupiter, Saturn, Uranus and Neptune, as well as the New Horizons mission past Pluto and into the Kuiper Belt.

Translunar Podcast, courtesy of the Volkssternwarte München, available anywhere you get your podcasts. 

Image courtesy of NASA. 

Planetary Exploration

Viking Lander on Mars 1976

We humans have come a long way, evolving into a technologically advanced species. Over the past 60 years we have mastered the ability to send robotic spacecraft throughout the Solar System, getting a close up look at all of the worlds, even landing on some of them. As a young person in Los Angeles in the 1970s, I would regularly ride my bicycle to the Jet Propulsion Laboratory (JPL) and pick up the latest pictures from the Solar System, from the first landing on Mars in 1976, throughout the entire Voyager missions and fly-bys in the late 70s through the end of the 80s. I am personally moved to watch and learn as we (NASA, ESA, other space agencies) push the frontier and travel farther and wider in our own home solar system. 

I recently recorded a podcast for the Translunar series talking about Planetary Exploration. You can listen here. And for those of you in and around Munich, Germany, I will be delivering talks in English and in German at the Volkssternwarte München on the same topic in November 2024. 

NASA and the Planetary Society have amazing stories, reports and photos from these missions. If you like learning about our Solar System, you will be happy to find endless resources on their websites. 

Image courtesy of NASA. 

Saturn has no rings!

If you could get a good telescopic view of Saturn today, you would find that it has no rings. At least that would appear to be the case for several days as another rare phenomenon takes place in the Solar System. Of all of the beautiful objects in the sky, Saturn is one of those wonderful heavenly targets that can be seen from cities and country, from spacecraft and flying telescopes, and always impresses the viewer. The second largest planet in the Solar System, Saturn has the largest and most distinctive ring system (Jupiter, Uranus and Neptune also have ring systems). The detailed photographs sent back to Earth from the Voyager and Cassini spacecraft and the Hubble Space Telescope have given us stunning perspectives into the depth and intricacies of the Saturnian ring system.

Saturn's ring system is very thin (less than 50 feet thick), and when viewed 'edge-on' from Earth it is virtually invisible. Saturn, like Earth, has a tilt in its rotation such that it has seasons as it moves around the Sun in its 30-year orbit. Consequently, every 15 years we see the ring system from the side and for a short while it disappears from view altogether. Although the ring system is very thin, it is extremely wide -- about 170,000 miles across, making the system even bigger than Jupiter!

Saturn is currently moving its way westward across the constellation Leo the Lion and is not visible due to its proximity to the Sun in the morning sky. It will gradually emerge from the glare of the dawn and be visible before sunrise. By the end of the year it will be rising in the east just before midnight and by next spring will be a gorgeous evening object with its ring system back in view. Until then, enjoy Jupiter and its fascinating moon system -- except when they aren't there!