Mars rovers didn't just reach for the stars: They dug into the Red Planet dirt

Mike James

The Mars Opportunity rover's 15-year mission: To boldly go into Martian craters everywhere. But now that it's over, where does it rank in the grand scheme of unmanned space exploration?

From the “golden records” put on the Voyager spacecrafts - which offer alien listeners a taste of Chuck Berry, Bach and Mozart - to the Hubble’s telescope's ability to see hundreds of Earth-like planets, the Mars rover project has tough competition, both in terms of notoriety and scientific achievement.

But Spirit and Opportunity, the twin Mars exploration rovers, have a notable legacy: They are among the most hands-on probes that man ever launched into the cosmos, scouring all over the red planet, popping into craters, and roaming the dusty plains of an alien landscape. Among their major finds is evidence that the surface of Mars once had liquid water.

The rover Opportunity, lost to the complications from a Martian dust storm, was finally declared dead by NASA on Wednesday, five thousand, three hundred, and fifty-two days after landing. Its sister craft Spirit met its end in 2010.

"Robotic space exploration has become the heavy lifter for serious space science," Phys.org once wrote in a primer on the subject of unmanned exploration. "While shuttle launches and the International Space Station get all the media coverage, these small, relatively inexpensive unmanned missions are doing important science in the background."
 

NASA has overseen more than 1,000 unmanned space missions since 1958. Here's a look at other historic unmanned space missions and their accomplishments:

The Hubble Space Telescope: A View of the Infinite

The $2 billion Hubble launched in April 1990, becoming the first major optical telescope placed in space. Over the past 28-plus years, Hubble has streamed back key data on subjects such as dark matter and how planets form. Its images are considered to be some of the most important that man has ever received into the history of the universe. 

Voyagers Grand Tour: An Invitation for Extraterrestrials

The two voyager probes were part of what Space.com called NASA's "Grand Tour" of the outer solar system. Launched in 1977 on a 12-year flight to the gas giants Jupiter, Saturn, Uranus, Neptune and their moons, the spacecraft "returned stunning images and data of the outer planets and carried golden records bearing the images, greetings and sounds of Earth to the stars in case alien life forms should find them," Space.com reported. 

The Voyager message is carried by a phonograph record, a 12-inch gold-plated copper disk containing sounds and images selected to portray the diversity of life and culture on Earth. Both probes carry the records for any alien civilization that may intercept the spacecrafts, as they will likely survive for billions of years traveling through interstellar space.

Cassini-Huygens: A Glimpse of Saturn

The Titan probe, Huygens, entered and landed on Titan in 2005. Cassini was the fourth space probe to visit Saturn and the first to enter orbit.

Sixteen European countries and the United States made up the team responsible for designing, building, flying and collecting data from the Cassini orbiter and Huygens probe. The mission was managed by NASA's Jet Propulsion Laboratory in the United States, where the orbiter was assembled. Huygens was developed by the European Space Research and Technology Centre.

After several mission extensions, Cassini was deliberately plunged into Saturn's atmosphere on September 15, 2017, to prevent contamination of habitable moons.

MESSENGER: Space photographer of Mercury

MESSENGER (an acronym of MErcury Surface, Space ENvironment, GEochemistry, and Ranging) was a robotic spacecraft that orbited the planet Mercury, the first spacecraft ever to do so. The spacecraft was launched aboard a Delta II rocket in August 2004 to study Mercury's chemical composition, geology, and magnetic field.

It crashed into Mercury on April 30, 2015, after running out of fuel.

Galileo: Jupiter's first Earth visitor

Galileo was an unmanned spacecraft sent by NASA to study the planet Jupiter and its moons. It was launched on October 18, 1989, by the Space Shuttle Atlantis on the STS-34 mission. It arrived at Jupiter on December 7, 1995, via gravitational assist flybys of Venus and Earth.

Despite antenna problems, Galileo conducted the first asteroid flyby, discovered the first asteroid moon, was the first spacecraft to orbit Jupiter, and launched the first probe into Jupiter's atmosphere. Galileo's prime mission was a two-year study of the Jovian system.

This article originally appeared on USA TODAY: Mars rovers didn't just reach for the stars: They dug into the Red Planet dirt