Astronomy Picture of the Day . ... That event was remarkable because it was the first time an asteroid was detected in space before crashing into planet Earth's atmosphere. ... Orcus of the Outer Solar System . ... 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. ...