NASA spacecraft New Horizons crossed Neptune's orbit on its way to a terrestrial landing on Pluto. New Horizons reached this milestone on the 25th anniversary of NASA's Voyager 2 achieving the same accomplishment on Aug. 25, 1989.

 "It's a cosmic coincidence that connects one of NASA's iconic past outer solar system explorers, with our next outer solar system explorer," said Jim Green, director of NASA's Planetary Science Division of NASA Headquarters in the nation's capital.

Voyager 2 provided our first up-close look at Neptune which revealed unknown facts such as the planet's Great Dark Spot, a huge storm similar to Jupiter's Great Red Spot. A lot of information can be ascertained by observing objects from Earth but closing the distance undoubtedly provides greater clarity. Astronomers are hoping that New Horizons will be able to reveal answers about Pluto's mysteries, and also provide new information previously unknown.

"The feeling 25 years ago was that this was really cool, because we're going to see Neptune and Triton up-close for the first time," said Ralph McNutt, leader of the New Horizons energetic-particle investigation and member of the Voyager plasma analysis team. "The same is happening for New Horizons. Even this summer, when we're still a year out and our cameras can only spot Pluto and its largest moon as dots, we know we're in for something incredible ahead."

For example, scientists learned that the surface of Triton, Neptune's largest moon, is covered with frozen nitrogen, water ice, and dry ice. Additional details became known about Triton as a result of Voyager's journey, such as the composition of the moon's atmosphere, and the presence of a large core that makes up two-thirds of its mass. 

New Horizons launched on Jan. 19, 2006 from Cape Canaveral, Florida, and reached Neptune's orbit, about 2.75 billion miles from Earth, in a record eight years, eight months and six days. The spacecraft is projected to reach the dwarf planet Pluto on July 14, 2015.