NASA's Voyager 1 and 2 are still exploring the outer solar system and continue to communicate with us on Earth daily.

The identical spacecrafts launched a couple of weeks apart from one another. Voyager 2 left Earth on August 20, and even though it launched first, it got its name because it was expected to reach Jupiter and Saturn after Voyager 1.

According to NASA, few missions can match the many achievements of the Voyager spacecrafts during their 40-year journey. Voyager 1 became the first spacecraft and only human-made object to have entered interstellar space. Voyager 2 is the only spacecraft to have flown by Jupiter, Saturn, Uranus and Neptune.

Even though the Voyagers will not come near a star until 40,000 years from now, together, they have improved our understanding of the characteristics of the atmosphere of Jupiter. They also discovered the first active volcanoes beyond Earth at Jupiter's moon Io; hints of a subsurface ocean on Jupiter's moon Europa; encountered Saturn's largest moon Titan, where data showed a thick Earth-like atmosphere; found the icy moon Miranda at Uranus and spotted icy-cold geysers on Neptune's moon Triton.

Though they are incredibly far from Earth -- Voyager 1 is almost 13 billion miles away and Voyager 2 almost 11 billion miles -- they continue to communicate with NASA daily, sending back observations on our solar system. The significance of the Voyager is the vast amount of new knowledge of outer space it has provided and the interest in further exploration it's generated. That interest has resulted in the Galileo mission to Jupiter and the Cassini mission to Saturn, as well as the discovery of three new moons around Saturn using Earth-based instruments.

Today, this mission's legacy has made an impact in our culture, and has reached the film, art and music industries. Each spacecraft contains a "Golden Record," a 12-inch phonographic gold-plated copper capsule containing Earth sounds, pictures, and messages designed to give any possible alien who encounters the spacecraft an idea of what life on Earth is like. They are expected to last billions of years and could one day be the only traces of human civilization.

As for the future, it is expected that in the year 40,272 AD, Voyager 1 will come within 1.7 light years of an obscure star in the constellation Ursa Minor (the Little Bear or Little Dipper) and in about 40,000 years, Voyager 2 will come within about 1.7 light years of a star called Ross 248, a small star in the constellation of Andromeda.

Read this article:

Voyager probes fulfill 40 years of space exploration - CNN International