Robotic 'emissaries' sent by humanity to our solar system neighbors, carrying curiosity to explore deep space, becoming our eyes and hands, reviewing milestone missions.

A Brief History of Solar System Probes

Humanity's Eyes and Hands in Deep Space

Humanity's gaze has never ceased to turn to the stars. Over the past half-century, we have sent a series of brave robotic "emissaries" to our solar system neighbors. Carrying human curiosity, they venture to places we cannot yet reach ourselves, becoming our eyes and hands in deep space.

This note is not an exhaustive list, but a look back at some of these milestone missions.

Journey to the Inner Solar System (Mercury, Venus, Mars)

• Mariner program: A series of NASA missions in the 1960s and 70s that conducted the first close-up flybys and observations of Mercury, Venus, and Mars, sending back the first precious close-up images.
• Viking program: In 1976, Viking 1 and 2 successfully landed on Mars and conducted experiments to detect life in the Martian soil. Although the results are still debated today, they represent humanity's first long-term, complex scientific investigations on the Red Planet.
• Curiosity Rover: Landing on Mars in 2012, it is a mobile chemistry lab whose primary mission is to analyze the climate and geology of Mars to determine if the planet could have ever supported life.

The Grand Tour of the Outer Planets (Jupiter, Saturn, Uranus, Neptune)

• Pioneer 10 & 11: Launched in the early 1970s, they were the first to traverse the asteroid belt and conduct pioneering exploration of Jupiter and Saturn. They carry the "Pioneer Plaque," a gold-anodized aluminum plaque engraved with information about humanity and Earth, as a "calling card" to any unknown cosmic civilizations.
• Voyager 1 & 2: Launched in 1977, they are arguably one of the greatest missions in the history of space exploration. Using gravity assists, they efficiently visited all four gas giants and are still flying towards interstellar space. They carry the "Voyager Golden Record," which contains sounds and images of Earth.
• Cassini–Huygens: Entered orbit around Saturn in 2004 for a detailed 13-year study. It also released the Huygens probe, which successfully landed on Saturn's moon Titan.

Touching Comets and Asteroids

• Rosetta: An European Space Agency probe that successfully entered orbit around Comet 67P in 2014 and released the Philae lander for an unprecedented close-up study of a comet.
• Hayabusa: A Japanese probe that successfully landed on the asteroid Itokawa in 2005, collected samples, and returned them to Earth in 2010.

Recommended Reading

• Popular Science:
  • (Book) Aerospace Engineering: A Very Short Introduction by David W. Southwood.
  • (Book) The Interstellar Age: Inside the Forty-Year Voyager Mission by Jim Bell.
• Textbooks:
  • (Book) Spacecraft Systems Engineering edited by Peter Fortescue, Graham Swinerd, and John Stark.