Exploring the Planets

Mars Rovers: Opportunity

The Journey of Opportunity
Opportunity was sent to Meridiani Planum, a smooth area near the Martian equator. Based on infrared measurements made from orbit, scientists thought the surface had an abundance of hematite, an iron-rich mineral that often forms where water is present. The area also had outcrops of light-colored rocks that might have formed from sediments, rather than lava.

From its landing site in Eagle Crater, Opportunity traveled to Victoria Crater, about 10 kilometers (6 miles) away.
NASA/JPL/University of Arizona image, NASA/JPL/MSSS inset

Eagle Crater, Victoria Crater

This image mosaic taken by Opportunity's panoramic camera shows the informal names given to rocks on the outcrop along the inner edge of Eagle crater, where the rover landed.
Mars Exploration Rover Opportunity
NASA/JPL/Cornell Image


Vista from the rim of Victoria Crater.
Mars Exploration Rover Opportunity
NASA/JPL/Cornell images

Eagle Crater, Mars

After landing in a small crater, Opportunity found many tiny sphere-shaped nodules, dubbed "blueberries," that were rich in hematite and were probably formed by water below the surface. The blueberries average about 0.3 centimeters (1/8 inch) in diameter.
Mars Exploration Rover Opportunity, Microscopic Imager
NASA/JPL/Cornell image

Blueberries on Mars

Rocks Shaped by Wind, Water, and Acid
Opportunity discovered that the area's light-colored rocks have wavy layers that cut across each other in sets, a feature geologists call cross-bedding. On Earth these ripples in rock form when shallow flowing water deposits fine sediments that are then covered by wind-blown sediments during dry periods. So the rocks found by Opportunity result from repeated deposition by wind and water. Scientists studying the chemistry of the rocks in Eagle Crater also found evidence that this water was highly acidic.

This close-up view shows a rippled rock structure known as cross-bedding (marked with black and blue lines).
Mars Exploration Rover Opportunity, Microscopic Imager
NASA/JPL/Cornell/USGS image

Cross-Bedding on Mars

Comparing Mars and Earth
Scientists often look for similarities between features on Mars and Earth to understand how the same processes have changed the landscape of both worlds.

The white area is a playa lake located in the desert of Namibia in southwest Africa. The dune in the background is over 200 meters (650 feet) tall, among the highest in the world. The playa surface consists of dried chemical salts left behind after rare storms flood the lake. Similar processes likely formed the light-colored deposits Opportunity found in Meridiani Plains. Although that area was probably not wet all the time, it may have been able to support life. Conditions on ancient Mars were much more Earth-like than they are now.
Photo courtesy of J. Grotzinger, CalTech



The Spirit rover took this self-portrait using its panoramic camera. The camera can look down to image the rover, but the mast on which it is mounted is not in the camera's field of view. The rover appeared relatively free of Martian dust in December 2004 when the image was taken. Mars Exploration Rover Opportunity
NASA/JPL/Cornell image

Spirit Rover


Mars Exploration Rover Mission (MER) Principal Investigator Steve Squyres summarized the characteristics of the Spirit and Opportunity sites:

"The two destinations that we've been to are dramatically different from one another. The picture that we've put together of what Gusev Crater, where Spirit is, long ago, what that place was like, it was a violent world.

"This was a place that was dominated by meteoritic impacts, effectively creating huge explosions that would throw materials into the air. Volcanic explosions were going on. There was water, but it was mostly water beneath the ground. These impact craters and these volcanic vents would create explosions of steam. I mean it was a very violent place. In some respects, it had the characteristics that would have been favorable for life. There were probably hot springs, for example. But it wouldn't have been a very nice place to be.

"Meridiani Planum, on the other hand, where Opportunity is, the geologic record that we see there preserved in the rocks is more quiescent. It's a place that was pretty dry most of the time.

"There was a lot of water beneath the ground. And when I say water, what I really mean is sulfuric acid. You wouldn't want to drink this stuff. But there was this acidic water beneath the ground. It saturated the ground, and it would occasionally come to the surface and form pools and ponds and perhaps little streams, evaporate away, and when it evaporated away, it would leave salt deposits behind.

"And then these salt deposits would blow in the wind, and they would form dunes, and we see the record of those salty dunes preserved in the walls of Victoria Crater. So it was not exactly an evolutionary paradise either. There was acid. It was dry much of the time, but it's the kind of environment that would have been definitely suitable for some simple forms of life."