Epically detailed photos of Mercury

Mercury is the smallest and fastest planet in the solar system, racing through space at 105,000 miles per hour, circling the sun every 88 days.

But besides small size and swift speed, little was known about this mysterious planet until NASA's MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft became the first man-made instrument to orbit Mercury in 2011.

On Thursday April 30, NASA will crash land the spacecraft into the planet, leaving a 50-foot-wide crater. But before meeting its violent end, the spacecraft and its seven scientific instruments have uncovered many of the alluring planet's secrets —some, however, continue to defy understanding.

Here's a collection of some of the most incredible photos the spacecraft took that helped scientists better understand this small world. Some of these images have false coloring to highlight different minerals and features on the surface.

Mercury has a thin atmosphere that does little to protect it from asteroid impacts, which slam into its surface on a regular basis. Some craters on Mercury are billions of years old, but you can spot the more recent impact sites in light blue and white in this false-color image.

Here's a remarkable close-up of Mena crater. The white rays tracing across the surface are debris that an asteroid kicked up when it hit. Notice how the rays overlay some of the older impact sites. That's how scientists know that this 15.5-mile-wide crater was made relatively recently.

On the other side of Mercury is one of its most famous features: the giant Caloris basin, outlined here in tan in the upper right. The basin is 960 miles wide and relatively smooth. In fact, the tan regions in this false-color image mark some of the smoothest places on the planet where past lava flows have glossed the surface.