On January 15, 2004, NASA’s Opportunity rover landed on Mars (in Meridiani Planum), three weeks after its twin, Spirit, touched down on the other side of the red planet on January 4.

January 25 story of what happened this day in Science, Technology, Astronomy, and Space Exploration history.

Opportunity rover

Opportunity rover, also known as MER-B (Mars Exploration Rover – B) or MER-1, was launched on July 7, 2003, 28 days after its twin, Spirit (MER-A), which launched on June 10, 2003, as part of NASA’s Mars Exploration Rover program.

The Spirit and Opportunity rovers were named through a student essay competition. The winning entry was by Sofi Collis, a third-grade Russian-American student from Arizona.

On January 25, 2004, Opportunity landed in Meridiani Planum, a plain located 2 degrees south of Mars’s equator, three weeks after Spirit touched down on the other side of the red planet.

Both Mars Exploration rovers (MERs) had a planned 90-sol (Martian day) duration of activity (slightly more than 90 earth days). Spirit functioned until getting stuck in 2009 and ceased communications in 2010, while Opportunity stayed operational for 5,353 sols after landing.

Opportunity rover first images (sol 1)
This image shows one of the Mars Exploration Rover Opportunity’s first breathtaking views of the martian landscape after its successful landing at Meridiani Planum on Mars. On the left, the rover’s mast can be seen in a stowed position. The image was taken by the rover’s Navigation Camera on Sol 1 (January 25, 2004).

Mission objectives

The twin missions’ main scientific objective was to search for a range of rocks and soil types and then look for clues for past water activity on Mars.

Each rover was about the size of a golf cart, standing 1.5 meters (5 feet) high, 2.3 meters (7+1⁄2 feet) wide, and 1.6 meters (5 feet) long and weighing 185 kilograms (408 pounds).

The scientific objectives of the Mars Exploration Rover mission are to:

  • Search for and characterize a variety of rocks and soils that hold clues to past water activity.
  • Determine the distribution and composition of minerals, rocks, and soils surrounding the landing sites.
  • Determine what geologic processes have shaped the local terrain and influenced the chemistry. Such processes could include water or wind erosion, sedimentation, hydrothermal mechanisms, volcanism, and cratering.
  • Perform “ground truth” (calibration and validation) of surface observations made by Mars orbiter instruments. This would help determine the accuracy and effectiveness of various instruments that survey Martian geology from orbit.
  • Search for iron-containing minerals, and identify and quantify relative amounts of specific mineral types that contain water or were formed in water, such as iron-bearing carbonates.
  • Characterize the mineralogy and textures of rocks and soils and determine the processes that created them.
  • Search for geological clues to the environmental conditions that existed when liquid water was present on the Martian surface. Assess whether those environments were conducive to life.
Opportunity first Mars panorama, January 25, 2004
This is the first Mars panorama by the Opportunity rover. The image was taken by the rover’s Panoramic Camera on Sol 1 (January 25, 2004).

Scientific instruments carried by Opportunity and Spirit

NASA’s Mars Exploration Rovers Opportunity and Spirit carried the following instruments:

  • Panoramic Camera (Pancam): Consisted of two electronic stereo cameras that worked in combination to take detailed, multi-wavelength, 3-D panoramic pictures of the Martian landscape surrounding the Opportunity and Spirit rovers.
  • Navigation Camera (Navcam): A monochrome camera with a higher field of view but lower resolution, for navigation and driving purposes.
  • Hazcams: Two Black&White cameras with a 120-degree field of view, that provide additional data about the rover’s surroundings.
  • Miniature Thermal Emission Spectrometer (Mini-TES): Measures the different spectrums of infrared light, or heat, emitted from different minerals in rocks and soils. Mini-TES is specially tuned to look for minerals formed in water.
  • Mössbauer Spectrometer (MB): It determines the makeup and quantities of iron-bearing minerals in geological samples studied by the rover. MB can be placed right up to rock and soil samples for close-up study, and it also examines magnetic dust samples collected by the Magnetic Array on the rover’s deck.
  • Alpha Particle X-Ray Spectrometer (APXS): It reveals the elemental chemistry of rocks and soils by measuring the distinctive way different materials respond to two kinds of radiation: X-rays and alpha particles.
  • Rock Abrasion Tool (RAT): Its rotating, grinding teeth gnaw into the surface of Martian rock to reveal fresh mineral surfaces for analysis by the rover’s scientific tools.
  • Magnet Array: a scientific experiment that collects dust on the Mars Exploration Rovers, Spirit, and Opportunity. Magnetic grains in Martian dust are tiny pieces of the Red Planet’s past. The Magnetic Array collects the dust for analysis by scientific tools that identify the composition and present clues on the history of the dust particles.
  • Microscopic Imager (MI): The Microscopic Imager on the Spirit and Opportunity Rovers was a high-resolution camera that gives magnifying glass views of Martian rocks and soils. It scouts promising targets for detailed study and analysis by other instruments on the rover.
Opportunity Mars rover - artist conception
This artist’s conception portrays Opportunity on the surface of Mars. Opportunity traveled a distance of 45.16 kilometers (28.06 miles) and exceeded its operating plan by 14 years, 295 days (in Earth Time), and 55 times its designed lifespan. Image source: NASA

Top scientific results of Opportunity and Spirit missions

Opportunity and Spirit rovers find enormous evidence of Mars was awash in water billions of years ago, with good conditions for supporting microbial life.

Here are some of the rovers’ most significant discoveries about the red planet:

  • Salty waters on the Martian surface a long time ago: Opportunity found the mineral hematite, which typically forms in water. Water is key to life as we know it. Yet, acidic water soaked this area in Mars’ ancient past, making conditions harder for life to thrive.
  • Steamy Times in Ancient Hot Springs: While dragging a wheel, Spirit churned up soil and found 90 percent pure silica at “Home Plate.” On Earth, this kind of silica usually exists in hot springs or hot steam vents, where life as we know it often finds a hot, happy home. Perhaps ancient microbes on Mars did as well. Hydrothermal vents have been hypothesized to have been a significant factor in starting abiogenesis and the survival of primitive life.
  • Signs of volcanic activity: Spirit discovered that an ancient volcano erupted at “Home Plate,” the rover’s final resting place. Together, powerful steam eruptions from heated underground water produced some explosive volcanism. While violent, these extreme conditions can support microbial life on Earth. Once upon a time, maybe they did on Mars too.
  • Evidence of flowing water on Mars: Near the rim of Endeavor Crater, Opportunity found bright-colored veins of gypsum in the rocks. These rocks likely formed when water flowed through underground fractures in the rocks, leaving calcium behind. This proves Mars was more hospitable to life billions of years ago than it is today.
  • Discovery of clay minerals: Another evidence that Mars once had liquid water on its surface. Clay minerals formed in neutral-pH water. Of all the places studied by Opportunity, this environment at Endeavor Crater once had the friendliest conditions for ancient microbial life.
  • Martian craters: Opportunity has visited and studied the geology of over 100 impact craters of all sizes during its 14 years of mission on Mars. It has learned about the lives of craters: how they form and erode through time.
  • Long-Term Study of the Martian Environment: Opportunity has been continually monitoring Mars for more than 14 years. So, the rover has collected a wealth of scientific riches on the Martian environment by studying Mars’ clouds and dust, the opacity (tau) of its atmosphere, and how it affects solar panels (solar energy). This type of information will help inform future Mars missions.

Opportunity’s firsts

  • Opportunity is the first rover to exceed the marathon distance of travel on another world.
  • It holds the record for the steepest slope driven by any rover on Mars. On March 10, 2016, while trying to reach a target on the slope of Marathon Valley in Cape Tribulation, the Opportunity rover attained a slope of 32 degrees, the highest angle yet for any Mars rover as of 2023.

The end of the Opportunity mission – “my battery is low and it’s getting dark”

Opportunity Parting Mars Panorama
This image is a cropped version of the last 360-degree panorama taken by the Opportunity rover’s Panoramic Camera (Pancam) from May 13 through June 10, 2018. The view is presented in false color to make some differences between materials easier to see. Incomplete image frames appear in black and white. Color images taken with the rover’s Pancam are taken one color at a time requiring three images of the same subject to create full color. The rover did not have the time to photograph those locations using the green and blue filters before a severe Mars-wide dust storm swept in on June 2018. Image Credit: NASA/JPL-Caltech/Cornell/ASU. This is a resized version. You can download the full-size image from the NASA Mars website.

By June 10, 2018, when it last contacted NASA and sent its last photo to Earth, which shows the intensity of the dust storm, Opportunity had traveled a distance of 45.16 kilometers (28.06 miles). It exceeded its operating plan by 14 years, 295 days (in Earth Time), and 55 times its designed lifespan.

On June 12, 2018, it entered hibernation due to a huge dust storm. Mars has the largest dust storms in the entire solar system. These massive events can last for weeks and can even cover the entire planet. That just happened in Opportunity’s case, within a few days, the rover’s solar panels were not generating enough power to maintain communications.

Science reporter Jacob Margolis tweeted that the last message NASA got from Opportunity basically translated to, “My battery is low and it’s getting dark.”

NASA engineers hoped to re-establish contact with the rover, citing a recurring windy period which was forecast for November 2018 to January 2019, that could potentially clean off its solar panels. But, it never happened, and the rover never responded to any of the signals sent.

On February 13, 2019, after the spacecraft had failed to respond to over 1,000 signals sent since August 2018, NASA officials declared that the Opportunity mission was complete.


M. Özgür Nevres

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