Snowmen from Outer Space!

So these are pretty cool, huh? They'll called Snow Rollers and they're pretty rare. They show up on the northern plains of the US in the winter when conditions (snow, wind, temperature, moisture) are just right. Basically, the process is pretty straightforward: under strong winds, with sticky, fluffy snow, the wind rolls up the snow. Apparently gravity can make em too - the snow rolls down a hill and makes a snow roller. These were seen in Spokane, WA last year. They're about 2 feet high.

Of course, those folks who believe that crop circles were created by aliens (as opposed to stoned college kids with rope and 2x4s) believe that snow rollers are the work of aliens as well. Not sure what the purpose would be, exactly.

You'd need to ask them.