Even though spacecraft have visited Mercury in the past, the same hemisphere was always in sunlight for every encounter. One side was photographed, and the other side was a complete and total mystery. There could be a big smiley face there, and we’d never know it. Well, the mystery’s over. MESSENGER flew past Mercury on January 14th, 2008, and revealed the planet’s hidden side… mostly.
Mariner 10 was the first spacecraft to zip past the planet Mercury, making three flybys in 1974 and 1975. Because the same hemisphere was in sunlight, the spacecraft was only able to image half the planet.
On January 14th, 2008, NASA’s MESSENGER spacecraft captured this image of Mercury when it was about 27,000 km (17,000 miles) away from the planet. During this flyby, it filled in about half of the hemisphere missed by Mariner 10. So that means that there are still some parts hidden – waiting to be revealed in future flybys.
And so, did it see a smiley face? Nope. The hidden hemisphere was pretty much like the rest of Mercury revealed so far: craters, ridges, bright and dark regions. At the upper right is the giant Caloris basin; its western regions haven’t been seen by spacecraft before.
If you’re hoping for more photos, don’t worry. This is just a quick black-and-white image captured by MESSENGER. NASA is planning to release more detailed images, including colour photographs over the next few days, so stay tuned.
We’ll keep posting them as they’re released.
Original Source: MESSENGER News Release