Three Probes Hold Promise of Insights into Mars, the Red Planet

Dec. 21–Its desertlike terrain looks as if it were scooped from the American Southwest or the African Sahara. It is a mystery waiting to be solved.

When Mars swung close to the Earth this summer, as close as it has been in 60,000 years, thousands of curious stargazers searched out the planet’s uniquely reddish glow and pondered what it might be like to visit.

For those thousands, the next few weeks will be a Mars bonanza.

Three unmanned spacecraft, two from the United States and one from Europe, representing the efforts of 18 nations, are barreling toward the Red Planet, where they will attempt to land and overcome punishing odds.

If the solar-powered probes are successful, they will spend several months examining the soil, rocks and air for evidence that Mars was once, and possibly still is, suitable for microbial life.

The results could pave the way for more ambitious missions, including human exploration.

“It’s the logical destination for humans in the next decades,” said Wesley Huntress, director of the Carnegie Institution of Washington’s geophysical laboratory, at a U.S. House Science Committee hearing in October on the nation’s space exploration options.

“It’s the most Earth-like of all the planets in the solar system. It may have had life early in its history. It might possibly harbor microbial life below its surface today. One day in the future, it may become a new home for humankind,” Huntress said.

The camera and instrument-laden probes fast approaching Mars include NASA’s two six-wheeled robotic geologists, Spirit and Opportunity, at $410 million each, and Great Britain’s Beagle 2.

Named for the sailing ship of the 19th-century naturalist Charles Darwin, Beagle 2 is hurtling toward the planet in the embrace of the European Space Agency’s $350 million Mars Express, an orbital spacecraft. Beagle 2 is designed to separate from its mother ship and descend to the surface late Wednesday.

Spirit is on course to land on Jan. 3 and Opportunity on Jan. 24.

Historically, the odds point to success for only one of the three missions.

Over a 43-year period, nine of the 31 spacecraft launched to Mars by the United States, the former Soviet Union or its Russian successors and Japan have scored a success. The latest failure includes Japan’s Nozomi orbital spacecraft.

Launched in 1998, Nozomi was unable to overcome problems with propulsion and electronic equipment. The Japanese gave up on the Mars orbital mission that was to study the sun’s influence on the planet’s atmosphere earlier this month.

The casualty list includes nine of a dozen attempts to land on Mars. The computer-controlled transition from interplanetary cruise to a high-velocity plunge through the Martian atmosphere is a high-risk maneuver.

“One moment you are traveling 12,000 miles per hour, and six minutes later you are on the ground,” said Firouz Naderi, who manages NASA’s Mars exploration program at the Jet Propulsion Laboratory in Pasadena, Calif. “So a lot of things need to happen just right.”

More than 100 million miles from Earth when they reach their destinations, Martian probes are well out of the reach of ground control teams. Signals indicating a critical problem require 10 minutes to reach Earth. An instantaneous corrective response from the ground would take an equal amount of time to reach an ailing craft.

“You get one shot at it,” Naderi said. “As Earth people we have not been too successful with Mars. Our batting average is one out of three. That’s good if you are a baseball player, but not so good with a space mission.”

Mars Express, with its Beagle 2, marks Europe’s first attempts to reach Mars. Spirit and Opportunity represent NASA’s first bids to land there since a failed 1999 mission, the Mars Polar Lander, crashed because of a computer software error.

Nonetheless, U.S. spacecraft have done the most to unmask the Martian mystery. NASA’s 1997 Pathfinder and 1976 Viking I and II missions account for all of the past successful Mars landings. Their findings, combined with the efforts of NASA’s Mars Odyssey and Mars Global Surveyor, which have been orbiting since 2001 and 1997 respectively, suggest the landscape was sculpted in part by vast torrents of water that flowed billions of years ago when the planet must have been much warmer.

If their interpretations are correct, Mars underwent a puzzling change in climate.

The observations of Odyssey and Global Surveyor also suggest that Mars may retain the water but that the liquid seeped into the subsoil and froze.

Some of Global Survey’s most intriguing images are of steep gullies on the walls of the many meteor craters and cliff faces. The gullies hint at recent eruptions of underground water, possibly responding to some unseen heat source.

If the theory is accurate, water would evaporate rapidly once it emerged into the thin atmosphere, but the combination of subterranean heat and moisture offers the prospect of underground habitats for biological activity.

“We have evidence today that Mars may harbor habitats, places where life could exist today, not yesterday, not billions of years ago,” said Jim Garvin, NASA’s chief Martian scientist. “We are not saying life is there today. But habitats may exist,” he told a meeting of the American Astronautical Society in Houston last month.

Encased in a clamshell structure, the 73-pound Beagle 2 is equipped with a small chemistry lab, mechanical arm, a drilling tool and other lightweight instruments. Once on the surface, the stationary lab will extend the 3-foot arm, collect crumbs of soil and rocks and deposit them in the lab. Sensitive instruments will look for chemical signatures of past and present life.

Without success, NASA’s better-funded Viking I and II missions made similar attempts a quarter-century ago.

The golf cart-size NASA Spirit and Opportunity rovers are designed to roam for short distances, evaluating the rocks and soil for telltale signs of how they were deposited, possibly by water, during an earlier era.

Another bid by NASA to look for life on Mars is probably at least a decade away, when the agency hopes to launch a more complicated and expensive robotic mission to retrieve soil and rock samples and fly them back to Earth for analysis.

Since their launch on June 2, June 10 and July 7, Mars Express-Beagle 2, Spirit and Opportunity have successfully weathered a few difficulties, including waves of high-intensity radiation from solar storms.

The English spacecraft was designed for six months of operations after landing. Spirit and Opportunity were designed for three months of operations.

NASA ROVERS

Spirit details:

— Launch: June 10, 2003

— Location: Cape Canaveral, Fla.

— Launch vehicle: Delta II 7925

— Scheduled Mars arrival January 4, 2004

— Landing site: Gusev Crater 2°S, 355°E

— Nominal mission end: April 6, 2004

Opportunity details:

— Launch: July 7, 2003

— Location: Cape Canaveral, Fla.

— Launch vehicle: Delta II 7925H

— Scheduled Mars arrival January 25, 2004

— Landing site: Terra Meridiani 15°S, 176°E

— Nominal mission end: April 27, 2004

BEAGLE 2

Mission details:

— Launch: June 2, 2003

— Location: Baikonur, Kazakhstan

— Launch Vehicle: Russian Soyuz/Fregat

— Planned Mars arrival: December 26, 2003

— Nominal mission end: November 12, 2005 (one Mars year after arrival)

Spacecraft details:

Mass

— Total: 1108 kg

— Instruments: 113 kg (7 instruments)

— Lander: 60 kg

— Body: 507 kg

— Fuel: 428 kg

Spacecraft size

— Body: approximately 1.2 m by 1.8 m by 1.4 m

— Solar panels: extended, about 12 m tip-to-tip

— High gain antenna: 1.8 m diameter

— MARSIS antenna: 40 m long

Mars orbit:

— Highly elliptical, nearly polar

— Altitude: 259 to 11,560 km

— Period: 7.5 hours

— Mission cost:

— Orbiter: roughly 150 million

— Lander: roughly 42 million

MARS IN BRIEF

— Heritage: Named for the Roman god of war, the planet Mars is easily identified in the Earth’s night sky as a small but bright reddish point of light. The color comes from the fine highly oxidized orange-brown soil that blankets the terrain.

— Location, location, location: Fourth planet from the sun, Mars lies just beyond the Earth in the nine planets of the solar system. In August, the neighboring planets made their closest approach in 79 years. The distance between the Earth and Mars ranges from 35 million to 233 million miles as they circle the sun.

Once every 26 months, the two planets align favorably so that a spacecraft launched from the Earth on low cost rocket can reach Mars in six to seven months.

One Martian year equals 687 Earth days. The rotation period equals 24 hours, 39 minutes, slightly more than the Earth’s.

The planet’s axis is tilted 25 degrees, slightly more than the Earth’s, giving the Mars spring, summer, fall and winter seasons.

— No garden spot: Because Mars is smaller and less massive than the Earth, the gravitation force is just one third as strong. A 240-pound linebacker would weigh just 80 pounds.

The temperature averages minus 64 degrees Fahrenheit, with extremes that range from minus 200 degrees to plus 80 degrees.

The atmosphere of carbon dioxide is so thin, moisture quickly evaporates. Winds that gust to 80 miles per hour can kick up global dust storms. Without a protective ozone layer, deadly ultraviolet radiation from the sun streams to the surface.

— Martian wonders: Major geographical features include the volcano Olympus Mons, which towers 16 miles high and 370 miles across. Valles Marineris, the largest known canyon in the solar system, spans 2,500 miles and ranges from three to six miles deep. Like the Earth, Mars has icy caps at its north and south poles.

Two small moons, Phobos and Deimos, named for the horses that pulled the chariot of the Roman god of war, circle the planet.

— Mystery for the ages: The rugged, sharply-etched surface of Mars suggest the planet’s terrain was shaped long ago by flowing water, a sign the climate was possibly once wet and warm enough to sustain some form of life.

So, where is the water now?. Has it seeped below ground and or accumulated in dust-covered glaciers? Did microbial life take refuge as well, perhaps below the surface or deep in the interior of rocks.

Centuries of speculation about life on Mars have made it a popular topic of science fiction. H. G. Wells’ 1898 novel “The War of the Worlds,” a fictional account of a Martian invasion, was brought to life so vividly in a 1937 radio broadcast by actor Orson Welles that many believed the Earth was actually under siege.

Sources: NASA, Encarta Encyclopedia, Destination Mars In Art, Myth, and Science

ROVER MISSION LIKE ‘HOMEWORK’ FOR FUTURE

If experts hope to prove that Mars harbors some form of life, or once did, they will probably have to retrieve pieces of soil and rock and return them to Earth for analysis.

That task will likely fall to a robotic spacecraft sometime in the next decade.

Though part of a long-term effort by NASA to solve that mystery, neither the Spirit nor Opportunity missions is equipped to make that determination. Instead, the robotic rovers will look for evidence in the rocks and soil of Mars that the arid planet was once wet and warm.

Though Great Britain’s Beagle 2 will look for traces of organic chemicals on Mars that form some of the building blocks for life on Earth, the spacecraft is not equipped to isolate and take images of microbes.

NASA’s Viking I and II missions became the first spacecraft to reach the Martian surface in 1976. Though highly successful in their efforts to photograph the Martian geology and characterize the weather, the Viking missions failed in the first-ever attempt to find evidence of organic chemicals on Mars.

Just last year, the National Research Council, a U.S. government-chartered think tank that advises Congress and federal agencies on major technical and scientific issues, concluded the only credible way to settle the question of life on Mars was to launch a “sample return” mission.

Estimated at $1 billion to $2 billion, the complex mission would require an advanced robotic spacecraft that could reach a landing site, gather samples and return them to Earth. Then, skilled scientists in laboratories with scanning electron microscopes and other state-of-the-art equipment could make the determination.

Less rigorous experiments on Mars with robotic equipment are likely to be too restrictive in their design or fail to make clear-cut distinctions between chemical activities associated with life processes and those that are not, the research council concluded in its report entitled, “New Frontiers in the Solar System: An Integrated Exploration Strategy.”

Even a favorable outcome would raise the spectre that Earthly microbes somehow survived the journey to provide the positive result, according to the report.

The technology for a sample return mission will probably not be available until a 2014 launch opportunity.

Until then, NASA plans to launch increasingly more sophisticated orbital reconnaissance and lander spacecraft to Mars to help scientists find the most promising target for a sample return mission.

“The bottom line is that because this will be a very very expensive mission and very, very scientifically important, we better do our homework as well as we can first,” Ed Weiler, NASA’s associate administrator for space science, said recently at the Johnson Space Center.

“There is no question we have to go forward with a sample return mission,” said Weiler. “It’s just when we do it, and it’s got to be to the right place.”

— By Mark Carreau

MARS EVIDENCE ON EARTH

Of the more than 7,500 known meteorites found on Earth, only 12 are certain to have come from Mars.

— The Martian meteorites are basalts and related rocks, with a total mass of only 80 kg.

— Martian water is recorded in the meteorites by alteration minerals, deposited from the water or formed by chemical reactions with the water.The most abundant of the alterations are veinlets of clays, hydrous iron oxides, and salt minerals.

— The oldest Martian meteorite, ALH84001, is devoid of water-bearing alteration minerals but does contain minerals.

GOLF CART-SIZE ROVERS BORROW A PAGE FROM PATHFINDER

Rob Manning’s spirits soared as never before on July 4, 1997, when NASA’s ground-breaking Pathfinder spacecraft bounded onto the surface of Mars, successfully delivering a small robotic rover called Sojourner.

“There was an incredible rush,” recalled Manning, who served as chief engineer for the $265 million mission developed by NASA’s Jet Propulsion Laboratory. “There’s all these different emotions you go through. It’s not just the success — that it’s working. It’s also this wonderful feeling of discovery, of feeling like, ‘Oh my gosh. I’m on Mars, now.’ “

Manning serves in an equally vital position now: manager of the entry, descent and landing preparations for NASA’s two Mars Exploration Rovers, Spirit and Opportunity.

Closely patterned after Sojourner but much larger and more scientifically capable, Spirit and Opportunity are to land late on Jan. 3 and Jan. 24.

As large as golf carts, Spirit and Opportunity are solar-power, six-wheeled robotic geologists equipped with cameras and a mechanical arm with drilling tools and instruments to examine the mineral make-up of the rocks and soil.

The robotic rovers were designed for at least three months of operation and can travel up to 44 yards a day.

Pathfinder was only the third spacecraft to successfully reach the Martian terrain. NASA’s Viking I and II landers became the first and second in 1976.

Great Britain’s Beagle 2, part of the European Space Agency’s Mars Express mission, aims to become the fourth late on Dec. 24.

Like Pathfinder, Spirit and Opportunity will attempt to land, using first parachutes to slow their descents and then small braking rockets and a cushion of airbags to absorb the final impact.

The task is so challenging that NASA will consider the $820 million effort a success even if one spacecraft is lost.

“We built two rovers because of the science opportunity, but a side benefit of flying a pair of the spacecraft, hopefully, is that it increases the opportunity for mission success,” said Ed Weiler, NASA’s associate administrator for space science. “Minimal success will be safely landing and operating one of the rovers.”

NASA turned to Pathfinder’s landing strategy after the Dec. 3, 1999 loss of the Mars Polar Lander. Designed to land using a parachute and a descent rocket, Polar Lander was never heard from again after the probe began its plunge into the Martian atmosphere.

Eventually, investigators found a software error that went undetected before the mission was launched. The error likely triggered the descent rocket to shut off early.

“Sure enough, when it didn’t work, those emotions were wildly different,” said Manning, who was at the time assigned to another Mars project. “There’s feelings of almost nausea, frustration. It’s a whole other set of feelings.”

Spirit and Opportunity will aim for widely separated landing sites on Mars. The sites were selected from among 155 for their scientific merit as well as for not being too rugged.

The landings of Spirit and Opportunity will require more precision than Pathfinder. The landing target for the 1997 mission was an elongated circle that stretched 120 miles long and 20 miles wide. Spirit and Opportunity will aim for ellipses less than half as long.

The risky landing has been simulated thousands of times by computer and rehearsed by NASA control teams, but danger lurks.

The probes spend nearly seven months getting there and then plunge into the Martian atmosphere at more than 12,000 miles per hour.

After parachutes and cushioning airbags deploy, seconds before impact, the two probes will still strike the ground with enough force to bounce as high as 50 feet, said Peter Theisinger, NASA’s Mars Exploration Rover project manager.

Surrounded by the airbags, the spacecraft could continue to bounce and roll for four minutes, covering up to two miles before halting.

Fabricated from a tough synthetic fabric similar to the material used in bullet-proof vests, the airbags inflate eight seconds before impact. They are larger than those that successfully protected Pathfinder.

In addition, an internal airtight bladder has been added in case the outer layer is punctured by what has been calculated to be the biggest threat, sharp-edged boulders that measure less than two-feet wide.

The landing system has been fortified with three small steering rockets to counteract strong wind shears that could cause the spacecraft to sway beneath their parachutes.

With the two missions timed to plunge to the surface just three weeks apart, the space agency faces a new challenge: rescuing the second rover if the first fails.

“Lots of what my team is doing now, in addition to testing to make sure everything works, is to figure out what happened afterwards from the data we get back,” said Manning. “If we don’t get any signals back after (Spirit) lands, how do we use the information we do have to improve the chances for the (Opportunity) landing that is just three weeks away?”

Spirit and Opportunity are equipped to communicate with control teams on the Earth in two ways. One is through direct radio transmissions back to Earth.

The second is through NASA’s Mars Global Surveyor and Mars Odyssey, reconnaissance craft that have been circling the planet since 1997 and 2001 respectively. When they are in range of the landers, the two orbiters can relay signals from Spirit and Opportunity to Earth.

In Spirit’s case, Global Surveyor will be in range and listening for the rover as it descends. Within 15 minutes of Spirit’s landing, the Earth will drop below the Martian horizon and be unable to receive direct signals from the probe.

Since the Earth will not rise again on Mars for another 12 hours, Spirit must respond to pre-programmed commands to retract the deflated airbags, open a protective shell, unfold power-generating solar arrays and snap the first images of its surroundings.

If ground control teams are fortunate, a signal and perhaps the first photographs transmitted could reach Earth within the first hours.

Even with flawless descents, Spirit and Opportunity could spend nine days on the surface and perhaps longer preparing to make their first trek, said NASA’s Jennifer Harris Trospher, the Spirit mission manager.

The time will be spent remotely deploying a dish-shaped communications antenna and a short mast with a two-eyed camera, unfurling the three pairs of wheels and raising the spacecraft from the crouched stance required for its journey.

But it’s also possible that the spacecraft could land off kilter, slowing deployment of the communications antenna.

“The expectation we have is that there are enough things that could go wrong in that time frame, that we won’t be worried in any way if we not hear from it for (two days),” said Trospher. “Your level of concern does raise each day. Probably by the beginning of the third day, if we have not heard anything through any of the links, we would be concerned. (But) we certainly would not give up.”

— By Mark Carreau

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