This picture shows Meridiani Planum, which is where Opportunity landed. The yellow oval, which is 81.5 km (50 miles) long, shows the area that Opportunity landed within. Click on image for full size (73K JPEG) Image courtesy NASA/JPL.

Two Mars Exploration Rover (MER) vehicles landed on Mars in January 2004. The second, named "Opportunity", landed at a place called Meridiani Planum. Meridiani Planum is a flat plain ("planum" means "plain"); a safe place to land! Opportunity actually ended up inside a small, shallow crater that is about 20 meters (66 feet) across.

Scientists think a mineral named gray hematite might be found at Meridiani Planum. On Earth, gray hematite usually forms in wet places. Scientists want to know whether some places on Mars used to be wet. Opportunity is looking for rocks that may have formed in wet places. That is why Opportunity landed at Meridiani Planum.

Meridiani Planum is near the equator on Mars. It is also near the Prime Meridian on Mars; that's where the name "Meridiani" comes from. The Prime Meridian is the place on a planet where the longitude is equal to zero. The Prime Meridian on Earth passes through Greenwich, England.

Opportunity is on the opposite side of the Red Planet from its twin rover, Spirit. Spirit landed at a place called Gusev Crater.