Proponents insist Mars science is vital for the U.S. More visits to our neighbor could answer lingering questions about Earth's history, reinforce U.S. prestige and get more children interested in science.

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LOS ANGELES — Saturn has its famous rings and Jupiter is the granddaddy of the solar system, but no planet has entranced earthlings quite like Mars.

Humans have launched 40 spacecraft to the Red Planet, lured by the prospect that life once might have existed in what is now dry rocks and sand. The latest machine to make the journey is NASA’s Mars Science Laboratory, a hulking, souped-up lab-on-wheels that will plunge toward the Martian surface late Sunday.

As the excitement builds, some wonder: Is Mars exploration a good investment?

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It doesn’t come cheap. It’s hard to calculate a total price tag, but over the 48 years NASA has been launching missions to Mars, Americans have spent a significant sum. The Viking missions alone cost nearly $1 billion in 1970s dollars. The twin rovers Spirit and Opportunity cost a total of about $1 billion to build and operate.

Curiosity, as the Mars Science Laboratory rover is known, is over budget at $2.5 billion.

Some in the federal government have suggested it’s time to roll back the spending. President Obama’s fiscal plan for 2013 would cut NASA’s funds for Mars exploration from $587 million to $360 million.

Proponents insist Mars science is vital for the U.S. More visits to our neighbor could answer lingering questions about Earth’s history, reinforce U.S. prestige and get more children interested in science.

It also could bring humanity closer to answering the ultimate question: Are we alone in the universe?

“It’s the search for the meaning of life,” said Alden Munson, a senior fellow at the Potomac Institute for Policy Studies, a science and technology think tank based in Arlington, Va.

Tickling the imagination

America’s love affair with Mars can be traced to astronomer Percival Lowell, who turned his telescope to the Red Planet in the 1890s and thought he saw an intricate system of canals that must have been built by intelligent beings. While never found, Martians became a science-fiction mainstay.

Earthlings got their first up-close view of Mars’ rocky surface in 1965, when Mariner 4 flew by and photographed a landscape that appeared as dead as the moon’s, lacking water or active geology, two prerequisites for life.

But later missions, from 1971’s Mariner 9 orbiter to the 2004 landings of rovers Spirit and Opportunity, helped establish Mars as a useful comparative laboratory for studying climate and geophysics on Earth. They demonstrated the planet was once warmer and wetter than it is now. Long ago, it may have been a hospitable cradle for life.

When planetary scientists assembled recently at the behest of the National Academies to set research priorities for the next decade, the search for conditions that would allow life to emerge on Mars topped the list.

“If there’s life or past life on Mars, it means the chances that life exists somewhere else are much higher,” said David Paige, who studies the moon and terrestrial planets at UCLA. If Mars is barren, “it might make Earth more unique than we thought.”

Some experts question the wisdom of focusing so intently on a single planet. Jupiter’s moon Europa, which is covered with an ice-encrusted ocean, could have the potential to harbor life; Saturn’s moon Titan, rich in organic chemistry, also might.

“It’s like the person who loses their keys and only looks for them below the streetlight,” said David Jewitt, a planetary scientist at UCLA who studies comets.

But money for planetary science is limited, and even those who favor a broader search admit Mars remains the most practical site to explore.

A mission to Europa, for example, would take about six years to reach its destination. Curiosity’s trip to Mars took about eight months.

Europa has other drawbacks: Particles flung into space by Jupiter’s magnetic field would likely fry a spacecraft’s electronics in weeks, said the University of Arizona’s Richard Greenberg, who studies the frozen moon.

“Personally, I love Europa,” he said. “But objectively, both it and Mars are great places to look for life.”

High-risk mission

Curiosity’s descent and landing late Sunday — after a voyage that began Nov. 25 and covered 354 million miles — will be complex and hair-raising. The destination is a deep crater with a 3-mile-tall mountain that NASA could only dream about using as a landing site until very recently.

It’s the most high-stakes mission ever to another planet. It was also described last week by the agency’s top scientist, former astronaut John Grunsfeld, as “the most important NASA mission of the decade.”

“There is no doubt that this is a risky mission, and that is coming from a human-spacecraft guy,” he added. “It’s hard to get something this big and complex to the surface of Mars, and then to get it to start roving. Thousands of people around the world working on it will be feeling their lives are riding on the mission landing successfully. We’ll all know soon if the risk was worth it.”

The mission’s goal is not to find Martian life per se, but rather to ferret out carbon-based organic compounds that are building blocks of life and then to determine whether the Gale Crater landing site was ever suitable for living creatures.

Curiosity, on which Boeing was a major contractor, has numerous ovens to bake soil and rocks up to 1,800 degrees and analyze what comes out; it has a laser zapper to free up potentially important targets in rocks; it has cameras with unprecedented capabilities, including one scheduled to take video of the last several minutes of the high-drama landing, dubbed “seven minutes of terror” by NASA.

The Curiosity mission is scheduled to last for two years, but it could continue if funding becomes available. The rover’s power source is a nuclear battery that, if all goes according to plan, could move the rover and keep it warm for years longer.

The prestige factor

Space exploration is the ultimate status symbol. China and India have signaled their technological aspirations by establishing space programs. So have Iran, Pakistan, Venezuela, Israel, Mexico and dozens of other countries.

“I’m afraid if we step back, it will be decades before we get back to Mars,” said Rep. Adam Schiff, D-Calif., whose district includes NASA’s Jet Propulsion Laboratory in La Cañada Flintridge, where Mars missions are based. “We have the expertise now. No other countries have been able to do this.”

NASA has outperformed other space agencies by a wide margin, completing 13 successful missions (against five failures) since 1964. The Russians have had particularly bad luck, with 15 failed missions and four partial successes.

The amount of money Americans devote to Mars is tiny compared with annual expenditures on other NASA projects, said Munson, who noted that in 2011 alone, the agency spent more than $4 billion on the international space station and the fleet of space shuttles.

The James Webb Space Telescope, successor to the Hubble Space Telescope that is designed to help scientists study the very early universe, is costing NASA $8.8 billion.

Even that price tag is dwarfed by the more than $600 billion the Defense Department will spend in 2012.

UCLA’s Jewitt put it like this: Americans spend more than $7 billion a year on potato chips.

“We’re talking about a small amount of money in the grand scheme of things,” Paige said.

Even those who’ve caught the Mars bug and are excited about Curiosity worry that with the new rover, NASA has “put all the eggs in one basket,” said Robert Zubrin, an aerospace engineer and founder of the Mars Society, which advocates for manned missions to the planet.

When NASA’s Mars Climate Orbiter and Mars Polar Lander both failed in 1999, work already was under way on several other missions that turned out to be successful, Zubrin said. But there’s not much that’s waiting in the wings this time around.

After Curiosity, NASA’s planetary scientists have only one major mission lined up: an orbiter, MAVEN, which will explore the Martian atmosphere and climate. It is scheduled for launch in 2013.

Material from The Washington Post is included in this report.

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