Marek Rosa's dev blog discusses the latest patch for Space Engineers, which adds planets to the space game, "because you wanted them." He explains "Space Engineers now has the largest, fully destructible, volumetric and persistent planets in the universe," pointing the way to this forum post with patch notes for the new version 01.108 and this trailer showing off the new version in action. There are even more videos in the blog post, and here's a bit on what to expect:

Planets are fully destructible, volumetric and persistent. You can drill a hole from one pole to the other, but you will have to put a lot hours into it. Planets have up to 120 km in diameter, which is a surface of 45 238,93421 km2! Even with planets this huge we had to apply smart visual tricks so they appear nice and round from afar. That’s why mountain ranges goes flat once you hit a critical distance from the planet.

Every object on a planet surface is affected by its gravity, which is why we added a new option for station grids - the Station voxel. By enabling this option a station will be static only when touching the voxel (one block build “inside of it”). When you cut some parts of the station away it will become a dynamic object and could break apart. And since you will be building stations on a spherical surface from now on, buildings can't be axis-aligned, but you can orientate the block so that it’s aligned with the landscape surface.