Astronomy Picture of the Day . ... 90482 Orcus was first discovered in 2004 and is slightly smaller than Pluto, although still one of the largest Kuiper belt objects known. ... Both Opportunity and its sister rover Spirit are in their sixth year on Mars, exploring the red planet for years longer than original expectations. ... To others it may look like a grazing seahorse, but the dark object toward the image right is actually an inanimate pillar of smoky dust about 20 light years long. ...