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Mars Exploration Rover - Opportunity

Mars Exploration Rover - Opportunity mission graphic

Phase: Operating

Launch Date: July 07, 2003

Mission Project Home Page -

Program(s):Mars Exploration

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This image from the microscopic imager on NASA's Mars Exploration Rover Opportunity shows spherules up to about 5 millimeters in diameter. Opportunity discovered spherules like these, nicknamed "blueberries," at its landing site in "Eagle Crater," and investigations determined them to be iron-rich concretions that formed inside deposits soaked with groundwater.

Researchers hypothesize that some layer beneath the surface in Victoria Crater's vicinity was once soaked with water long enough to form the concretions, that the crater-forming impact dispersed some material from that layer. Opportunity might encounter that layer in place if the rover drives down into the crater.

Image Credit: NASA/JPL-Caltech/Cornell/U.S. Geological Survey

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The Mars Exploration Rover (MER) Opportunity landed on Mars on January 25, 2004. The rover was originally designed for a 90 Sol mission (a Sol, one Martian day, is slightly longer than an Earth day at 24 hours and 37 minutes). Its mission has been extended several times as it continues to make new and profound discoveries about the red planet.

Opportunity is equipped with a powerful set of tools to study a diverse collection of rocks and soils that may hold clues to past water activity on Mars. These tools include multiple cameras: a panoramic camera (Pancam), as well as a navigational camera (Navcam), and a microscopic imager (MI) which obtains close-up, high-resolution images of rocks and soils. There are also several instruments for analyzing composition and mineralogy: a miniature thermal emission spectrometer (Mini-TES), a Mossbauer spectrometer (MIMOS II) which provides unique information about iron-bearing minerals, and an alpha particle x-ray spectrometer (APXS) which tells us the chemical makeup of individual rocks and soils. Finally, the rovers are equipped with a “rock abrasion tool” (RAT) which exposes fresh material beneath the dust and weathered rinds that typically coat martian rocks.

Opportunity landed on the opposite side of Mars from its twin, Spirit, on a flat plain known as Meridiani Planum. This region had been chosen because the Mars Global Surveyor mission had identified concentrations of the mineral hematite there and on Earth the presence of hematite is often associated with water. Opportunity’s landing is often referred to as a “hole-in-one” because the spacecraft unexpectedly came to a rest inside a small crater. Opportunity did indeed find hematite here, in the form of small concretions nicknamed “blueberries.” After thoroughly investigating its landing site, Eagle Crater, Opportunity traveled to several other craters, the slightly larger Endurance Crater, the shallow crater Erebus, and finally, after a long journey, to the much larger Victoria Crater, located roughly 7 km from the landing site. The layers of sedimentary rock exposed in the walls of these craters contain minerals, such as sulfites and jarosite, and chemicals, such as chlorine and bromine that require considerable interaction with water to produce. The evidence suggests that Opportunity’s landing site was once the shoreline of a salty sea.

Despite a few problems—Opportunity got stuck in a sand dune for over a month—the rover has exceeded expectations and continues to return exceptional data.

Opportunity on Mars - Eight Years and Counting - January 24, 2012 Animation
This narrated podcast, by John Callas, depicts key events of Mars Exploration Rover (MER) Opportunity.

8th Anniversary for Mars Exploration Rover Animation