Science is an inherently visual activity. Yes, we can know about all sorts of things in the abstract and try to envision them in our minds. But it's one thing to hear a description of the developing brain, and another thing entirely to see one as it's developing. In some cases, images tell us things that it was simply impossible to know otherwise.

2015's science came with its own host of images, some of them taken by the scientists and engineers involved, others we managed to take ourselves. So, we put together a gallery of some of our favorites from this past year; what follows is a little bit on why we liked them.

New worlds: Pluto is too small to have much heat left over from its formation, so the expectations were that we'd see little more than a crater-ridden landscape. Pluto is anything but, and the images have left scientists scrambling to explain a landscape with complex geology. Similar things are true about another dwarf planet, the largest object in the asteroid belt, Ceres. Here, the surface was a crater-scarred landscape, but it contained enigmatic bright spots that continued to grab everyone's attention as the Dawn probe moved closer.

Finally, while its rendezvous with a comet happened prior to 2015, Rosetta continued to send back images as the two of them swung by on their closest approach to the Sun.

Oh yes, and Mars has liquid water on its surface. Not just in the distant past, but now.

New ways of getting there: Blue Origin, Jeff Bezos' space company, has kept things very quiet while working on a rocket. But that changed after their New Shepard did a suborbital launch and then returned safely. Not to be outdone, Elon Musk's SpaceX nailed its landing, too, after successfully delivering a second stage on an orbital trajectory.

Of course, space is still a challenging location, as demonstrated when one of SpaceX's craft failed dramatically on its way to orbit this year. We have no great pictures of that, but this year saw the release of some apocalyptic images from last year's failure of an Orbital Sciences launch.

A different view of life: Most of the skeletons we have from near the time of the origin of our own genus, Homo, are fragmentary—a few pieces of just one part of the body. But the Rising Star expedition, broadcast online as it was happening, turned up nearly complete skeletons and parts of dozens of individuals, all from a previously unknown species that may be one of the earliest branches of the Homo tree.

Separately, we've always loved Nikon's annual microscope contest, because it often provides amazing views of things that are all around us, but not obvious. This year's plant and tadpole images fit that bill nicely.

Getting at the fundamentals: What's the Universe made of? That's the central motivating question of particle physics, which reached previously unprecedented energies at the upgraded LHC. We were lucky enough to visit during the renovation and took pictures while it was taken apart. We also managed to visit SLAC this year, where a particle accelerator has been used to build a high-energy X-ray source.

Listing image by Dr. Helen Rankin, University of California, Berkeley.