When it comes to exploring the Solar System, we haven’t exactly treated all planets equally. We definitely favour Mars—we’ve been roving the planet consistently for a little over a decade now—and don’t favour the outer ice giants Uranus and Neptune.
Those ice giants are far away and hard to get to, requiring long transit times and multiple gravity assists. That means only one spacecraft has visited those distant worlds: Voyager 2 flew past both in the 1980s. But lucky for us, scientists are still able to put that data to good use.
That includes Paul Schenk of the Lunar and Planetary Institute in Houston, who restored Voyager 2 images to give us the best look at Neptune’s moon Triton we’ve ever seen. (Here's the direct link to the full-res image, which is huge.)
Voyager 2 was the first of the pair to launch, leaving the Earth on August 20, 1977. It flew by Jupiter and Saturn on its primary mission before scientists redirected its trajectory to pass by Uranus and Neptune.
Where Neptune is concerned, it was a fortuitous move. Voyager 2’s revised trajectory took it closer to Neptune than it passed by any other planet on its tour; it flew within 3,000 miles of the planet’s north pole on August 25, 1989.
That close pass by Neptune also allowed Voyager 2 to get a look at the planet’s largest moon, Triton. And now, 25 years later, Schenk has restored the spacecraft’s images of the moon to piece together the cleanest and largest map we’ve ever seen. He’s even turned the images into an animation showing what the flyby might have looked like to a passenger on board the spacecraft.
The full map shows 1,970 feet of the moon in each pixel, bringing some of the Triton's mysteries to light. And it really is a pretty interesting little body. Triton’s surface “may be younger than a few million years and may be geologically active today,” Schenk wrote in a recent blog post about the new map, calling the moon one of the most fascinating bodies in the Solar System.
“Its maximum surface temperature is only 35 degrees above absolute zero, and yet volcanoes and geysers have remade its surface, possibly within the lifetime of the human species," he wrote.
The Voyager spacecrafts surprised scientists at every turn, revealing things like the volcanic activity on Jupiter’s moon Io for the first time in human history. But still, the apparent activity on Triton was a real shock. Schenk recalls legendary astrogeologist Larry Soderblom exclaiming during the press briefing when the first Triton images were revealed, “What a way to leave the Solar System!”
Whether or not this beautiful new map of one of the farthest moons will be enough to reignite interest in the distant ice bodies has yet to be seen. Not only are they quite different than the gas giants Jupiter and Saturn, that Voyager 2 was the only spacecraft to visit means we’ve only studied them with 1970s-era technology.
Imagine what we could learn—and the views we could see—with a Cassini-type spacecraft launched to and tailored for the most distant planets. It would be a long-term commitment to visit Neptune’s system with a dedicated mission, but worth it.