It may seem like we always know what's on the moon's mind.
After all, clouds permitting, we see the same face almost every night — sometimes winking, sometimes frowning and sometimes waxing downright ominous.
But there's another side to our nearest celestial neighbor that we rarely glimpse: the far side of the moon, also known as its "dark" side.
We did get a spectacular view of it last February, thanks to the Chinese micro-satellite Longjiang-2.
And, occasionally, as the moon teeters on its axis, we might glimpse as much as 18 percent of that side from here on Earth. But satellite and Earth-based views leave a little something to be desired in terms of intimacy.
So when China's Chang'e 4 lander and Yutu 2 rover touched down on the far side of the moon last year, we eagerly awaited the postcards. Chang'e 4 didn't leave us waiting long, sending home a stunning image of its landing site almost immediately.
Planetary scientist Briony Horgan described that side as "actually much more primitive" than the smooth serene side we see from Earth. It features a "really ancient crust that dates back to the very, very early solar system," she noted in an interview with NPR last January.
"There are rocks all over the far side that are over 4 billion years old. We're really excited to see what those look like, up close."
But we had to wait a year for the China National Space Administration (CNSA) to deliver the ultimate postcard payload.
As you can see, it was worth the wait. In fact, the just-released CSNA batch comprises an entire year's worth of images. That's because the lander and rover could only gather images during the 12 lunar days. Each "day" is the two-week stretch when the sun beats steadily down on the lunar surface before disappearing entirely for another two weeks.
During the dark stretch, the lander and rover power down to save energy. And when the sun beams again, Chang'e 4 and Yutu 2 hum to life, charging solar cells and snapping image after image. Lander and rover make a good team, with the former handling panoramic images and the latter imaging the terrain. Together, they sent 12,512 data files including radar and infrared spectrometry data.
Along the way, the lander and rover tandem are wending their way along the dark side — a place where no rover had tread before — collecting and analyzing soil samples. They brought our old friend flowers. Well, at least the seeds of a flowering plant, in the hope that flowers may one day bloom there.
That would certainly add another breathtaking element to future postcards from the moon. Not that these images don't provide enough gobsmackery; the far side of the moon manages to be strike a somber yet spectacular pose all on its own.
Keep in mind, despite the moon's seeming intimacy with our planet, it's 328,000 miles — or 30 Earths — away from us. But thanks to Chang'e 4 and Yutu 2, we've never had a clearer picture of our most stalwart celestial companion. And soon, we may even know its secrets.