In a study posted online May 9, Nathan Bridges and colleagues analyzed data from an eye-in-the-sky called Mars Reconnaissance Orbiter. Using a high-resolution telescope, the researchers measured the movement of sand dunes over a 105-day span.

The fine-grained images showed that the dunes are indisputably on the move, says Bridges, a senior scientist at the Applied Physics Laboratory at Johns Hopkins University. “Even though Mars has a very thin atmosphere and high-speed winds are rare, the dunes are moving.”

The research group saw movement both in entire dunes, and in the ripples on their surface. Across one meter of dune front, they calculated an annual sand movement totaling about 2.3 cubic meters. “If you had a children’s sandbox, that would fill it with sand in a year,” Bridges says.

On Mars, as on Earth

And that, he adds, is within the range of movement seen in some Earthly dune fields. “We are not making the case that Mars has the fastest dunes, but they do move like some on Earth. Mars is an active planet, maybe not as active as Earth, but we are seeing significant movement.”

How much wind is needed to move sand when the atmosphere is less than one percent as dense as Earth’s? The grains would start moving in a wind of about 20 to 30 meters per second (40 to 50 miles per hour, measured at a height of 1 meter), Bridges says. “That is about 10 times what you need on Earth, due to the atmospheric density difference.”

Such winds do blow — rarely — on Mars, but once the sand starts moving, it’s easier to keep it rolling, he says. “Recent research by my colleagues has found … a lower-speed wind can sustain the movement.” Under the reduced gravity of Mars, a grain stays aloft longer, giving the wind more time to accelerate it. When the high-speed grain hits the sand bed, a high-energy collision impels more sand grains into motion.

Mars: A moving planet

At any rate, the discovery proves that wind needs no help from water in moving dunes, Bridges says. “We have seen dunes in images since the 1970s, but there was a question, were they currently active, moving? Mars has a very thin atmosphere and it would need high-speed winds to move sand, and those are very rare. So it’s been an open question, how much sand is moving now, and was more moving in the past?”

On Earth, water is highly erosive, but Mars has no liquid water, “so one agent of erosion on Earth is lacking,” says Bridges. “There is a lot of evidence for erosion — craters that appear to be filled in with dirt, and the primary mechanism is wind.”

And lasting sandblasting

Wind does not just move sand — it also creates sand, Bridges says. His group calculated that the natural Martian sandblaster sand would erode 1 to 50 microns off rock per year, about the same rate as in Victoria Valley.

That sandblasting would provide a source of the sand that litters so much of the red planet, Bridges says. “Erosion is occurring today, so wherever you have sand, and moderate winds, you are likely to get significant amount of erosion from rocks.” That could then create silt or more sand.

When we see all these eroded terrains, “you don’t have to evoke any past climate to explain this,” he says. “It’s a current process, and it was likely occurring for billions of years.”

UPDATE 27 APRIL 2012: The retired space shuttle Enterprise will fly over New York City today, aboard a jumbo jet, as part of the move to its final resting place at the Intrepid Sea, Air and Space Museum on the Hudson River. END UPDATE

For advocates of space travel, the news is grim. In July, 2011, the last U.S. space shuttle was parked, as planned. Over 30 years, the shuttles helped build the International Space, but two explosions killed 14 astronauts, and each flight cost nearly half a billion dollars.

On August 24, 2011, a clogged pipe caused the crash of a Russian Soyuz rocket. Soyuz is a reliable space-truck whose ancestor launched Sputnik, the first artificial satellite, in 1957.

With the shuttles in the old-age home, any delay of a Soyuz launch to resupply the space station, planned for Nov. 14, 2012, could force the station’s evacuation.

Abandoning the space station after a decade of continuous occupation might have limited scientific impact, as the station is not proving to be a scientific bonanza as promised. (However, on Sept. 21, NASA reported that a Japanese astronaut did perform “bubbling experiments” on green tea before staging a “traditional Japanese tea ceremony.”)

The growing problem of getting into space got more attention on Aug. 24, when a sub-orbital space taxi built by Blue Origin, a company funded by Amazon founder Jeff Bezos, crashed in West Texas, setting back the nascent space-tourism industry.

People have been going into space for 40 years, but the process is neither cheap nor routine. For comparison, 40 years after the first automobiles, millions of cars were changing the U.S. economy and landscape. And 40 years after Kitty Hawk (1903), airplanes had circled the globe and become a dominant force in World War II.

So, 40 years after Yuri Gargarin became the first space-farer, why is it so hard to get people into space?

It’s the gravity, stupid!

The first clue to the difficulty of reaching orbit is evident in the controlled explosion needed to launch anything: reaching orbit requires a speed of almost 18,000 miles per hour and overcoming gravity.

And gravity is a stern customer.

Although gravity is fixed, a changing political backdrop has deprived the space program of its historic justification, says Howard McCurdy, a professor of public administration and policy at American University, and student of the space program. “The key problem, as a political scientist, was the end of the Cold War. Now the rationale for a lot of human space program is jobs, but in the absence of Cold War competition, we get these anomalies,” like thumbing a ride to space from your former enemy.

Faced with the prospect of being stuck on Earth, on Sept. 14, NASA administrator Charles Bolden announced the Space Launch System (SLS), a heavy-lift rocket and space capsule designed to reach earth orbit and beyond. “American leadership in space will continue for at least next half century,” Bolden said. “We have laid the foundation for success.”

Better than nothing?

The reaction to SLS was a bit ho-hum. The proposal “has been controversial because some say it’s just the same old technology, a combination of Apollo, Saturn V, and the shuttle, and we really should be advancing the technology, doing something new that will get us to deep space more quickly,” says astrophysicist Jack Burns, who has served on the NASA Advisory Council science committee, and is vice-president emeritus for academic affairs and research at the University of Colorado System.

But what else is there? Burns asks. “I look at SLS as a practical vehicle that will get a lot of mass into orbit, and then to the moon, the asteroids. Having a heavy lift vehicle, for the first time since the mid ’70s, when we did away with Saturn V, should be an important part of U.S. space architecture.”

The shuttle, whose demise has forced the current concern over space launching, was hatched in 1972, by Pres. Richard Nixon, who proposed a reusable, flying bus to reach low orbit and “take the astronomical costs out of astronautics.”

Getting to orbit didn’t turn out to be cheap: NASA chalks up the average price tag on 135 shuttle launches at $450 million.

Consternation over Constellation

In 2005, faced with mission failures and an aging shuttle fleet, Pres. George W Bush called for the shuttle program to end after the space station was constructed. As a replacement, Bush proposed Constellation, a new rocket, and Ares, a new spaceship, which would visit the moon and then Mars.

However much the Mars mission was beloved by space-travel enthusiasts, it carries certain health hazards…

Cost estimates for Constellation and Ares rose faster than a rocket and by 2010, the projects had black-holed $9 billion, and the guesstimated price of launching a single Ares-1 had reached $1 billion. So Pres. Obama trash-binned the twin projects and directed NASA to come up with something cheaper and faster – which turned out to be the poetically-branded “Space Launch System.”

The proposal has, as we’ve said, met grudging acceptance at best. “This is a turning point for all kinds of reasons,” says Michael G. Smith, a space historian at Purdue University. “The shuttle program is finished after 30 years — it was too expensive, too old — and the Bush program to take us to the moon is finished.”

Although NASA has another job — the SLS — the manned space program needs goals with more focus, Smith says. Because Obama has failed to set a clear challenge before NASA, “they have nothing to prove, no short-term mission.”

In a sense, Smith adds, the Obama plan conforms to American desires. “There’s a paradox. A Gallup poll says the American public wants a space program, and is proud of it, but does not want to pay for it, and that’s the Obama Administration approach: ‘We want something, we have announced something, without a clear-cut commitment to what it is.’”

Take the money and … design?

In an era that is short of cash and jobs, however, NASA has an immense constituency in its legion of employees, contractors and their employees, Smith says. “Lawmakers with NASA investment in their districts are challenging the administration’s lack of clarity.”

But viewing a space program as a jobs program is unlikely to maximize either cost savings or scientific breakthroughs. “NASA has half-lost the ability to innovate,” says McCurdy. “People are hunkering down like turtles, protecting what they have, playing defense to hang onto the field stations [such as Marshall Space Flight Center in Alabama], and Congress is pushing them in ways that are inefficient for cost reduction. Most members want to know if contracts are still going to their districts.”

Space is inherently expensive, and McCurdy questions whether the current NASA budget will accomplish much space travel, or mainly rocket design and construction. “A big issue for NASA is whether the budget for exploration is going to be sufficient to actually develop, build and test the rocketry,” he says. “It looks like it will be sufficient to provide aerospace jobs, but they need a little bit more money to bend metal.”

Confronting costs

It’s odd, McCurdy says, that developing a new rocket and space vehicle are expected to cost $100 billion, considering that Saturn V, which launched Skylab and the moon shots, cost about $10 billion in 1960 dollars. “Multiply that by five to get today’s price — $50 billion — and that included the production line, a test vehicle and the actual rocket.”

Much engineering has been done for Constellation and previous rockets, and McCurdy, who acknowledges that the engineering and manufacturing expertise and the Saturn assembly line have long disappeared, wonders why NASA cannot produce a heavy-lift rocket for $50-billion.

Cutting the budget to the bone can be penny wise and pound foolish, McCurdy adds. “Once they got the assembly line going for Saturn V, it was very efficient, but if they build only one rocket every two years, it becomes more of a craft rocket.”

What are the other options for launching people into space?

Government rocket, private rocket

International rockets such as Ariane have gotten into the satellite-launch business, but most of them are not powerful enough to take people into orbit, or to leave earth orbit and reach the moon.

China, with one satellite orbiting the moon, and an imminent launch of an 8.5 ton component for its first space station, definitely has the lift capacity, but we’ve not heard about any discussions about launching U.S. space equipment.

Government is not the only game in town, however, and many hope that the genius of private enterprise will fill the gap, even if some of the efforts are watered with buckets of federal funds. If you place a challenge before rocket manufacturers, “both the startups and old horses, somebody may come up with a breakthrough,” says McCurdy. Even so, he adds, NASA must still “pick a winner before knowing whether it is a working design, and they are no better at that than I am at picking stocks.”

So how is the private sector faring in the human space travel biz?

the private role

Corporations are contending for two roles in space. Many are interested in space tourism, a business that began in 2001 with a seven-day visit to the International Space Station but today is focused on sub-orbital flights – spending a few minutes in micro-gravity beyond the edge of the atmosphere:

Photo: Jim Campbell/Aero-News Network

SpaceShipOne, built by Scaled Composites, slung beneath White Knight, the mother ship that lifts it toward the edge of space.

Blue Origin, a secretive operation funded by Jeff Bezos, the Amazon.com billionaire, is working on “New Shepard,” a sub-orbital vehicle. According to the website, “We’re working, patiently and step-by-step, to lower the cost of spaceflight so that many people can afford to go and so that we humans can better continue exploring the solar system. Accomplishing this mission will take a long time, and … we do not kid ourselves into thinking this will get easier as we go along.” Blue Origin has a NASA contract to develop a taxi for hauling astronauts to orbit, but recently lost a spaceship at 45,000 feet.

Scaled Composites, an advanced aircraft maker, won the $10-million X-prize in 2004 for attaining 328,000 feet twice within 10 days. The firm is working with Virgin Galactic to enhance its a sub-orbital spaceship-mother-ship combination. Virgin says 430 private-nauts are already put down a deposit for flights that will cost $200,000.

Xcor Aerospace is also selling seats on an unfinished spaceship, for a suborbital flight priced at $95,000, starting with a spare-change deposit of $20,000. Buy now, and your seat-mate could be a Victoria’s Secret model… Honest!

Let’s really go to space!

Above the sub-orbital realm, however, comes the real high-technology interest: resupplying the space station, or reaching the moon or an asteroid. In this realm, one company has grabbed most of the headlines: SpaceX, founded by PayPal founder Elon Musk.

SpaceX is developing two types of “Falcon” rockets, and has a $1.6 billion NASA contract to launch 12 loads of cargo to the space station (the first flight is scheduled for Nov. 30), in NASA’s Commercial Orbital Transportation Services program. (Orbital Science Corp. is the other contractor in the program.)

In December, 2010, SpaceX became the first private company to launch and recover a spaceship. “The technology has advanced,” says Burns, “but so far SpaceX only has a couple of launches of the Falcon 9. It’s a long way from that all the way to orbit, with real live astronauts. It’s a risky venture.”

SpaceX says it emphasizes reliability, and the business end of Falcon 9 houses nine individual rocket engines. The rocket is supposed to reach space even if one engine goes kaplooey.

A human role remains

When President Ronald Reagan proposed and promoted what is now called the International Space Station, a howl went up among scientists who called it a diversion of resources from the more productive unmanned spacecraft. Carting people around raises the price and the stakes at every stage of design, production and operation, and these scientists accurately forecast a fruitful program of robotic exploration — everything from the Hubble Space Telescope, to the Opportunity and Sojourner rovers on Mars to the Galileo spaceship that explored Jupiter.

Those robots were awesome and inspiring, says Burns. “Opportunity is U.S. technology, it’s something we all should be proud of it, it has well exceeded its lifetime, the engineers were very clever in the design and operation. That good old-fashioned American ingenuity ought to get kids excited about going into science, engineering, math, whether that gets directed to space or something else.”

The manned vs. robot argument had merit in its time, given that the space station alone has cost NASA north of $50 billion (with other countries contributing about the same amount), and NASA never has enough money for all the scientists who write grants, which leads some critics to question whether the money is well spent, or would have been more productive if spent on funding conventional science.

But the manned vs. robot dichotomy may be fading, says Steven Collicott, a professor of aeronautics and astronautics at Purdue University, who placed an experiment about the fluid flow in micro-gravity on the space station. “There is a great benefit to doing both. The astronauts who have operated space station experiments I have been involved in have been incredibly creative thinkers, problem solvers.”

The flow experiment cannot be performed on Earth, Collicott says. “We do everything we can to test on earth, or on short-duration, low-gravity [aircraft] flights, but there are times when … the camera position needs to be changed, or a liquid gets trapped. An astronaut can unbolt and shake the experiment … or act on their observations to explore a new phenomenon immediately, without reprogramming, relaunching or rebuilding, which involves years and millions of dollars.”

Human hands, eyes and brains are irreplaceable, Collicott says. “If people were not needed for research of this type, why would we be spending money to send people to Antarctica each year?”

human vs. robot — the dichotomy wanes

“I never felt comfortable with the manned versus unmanned argument,” says Purdue’s Smith. “We have always pursued both [approaches]. Satellite, probes and telescopes… There is no ICBM [inter-continental ballistic missile] system without satellites, there is no exploration of the moon or Mars without the [robotic] probes we have sent there.”

More on the manned vs. robot issue…

Yet despite the phenomenal allure of space-telescope photos, manned exploration plays a critical motivational role, Smith adds. “Without an orbital station, and the public interest and international cooperation that revolve around it, NASA can’t do anything. Satellites and probes just don’t drive that public interest.”

What Smith calls “fierce debates” between astronomers, who favor robotic exploration, and engineers who favor manned exploration are “not about policy or philosophy, they center on funding; those seem to me very parochial questions.”

Burns offers one suggestion for merging people and robots: sending astronauts to a low-gravity point above the far side of the moon (which never faces Earth), where they could control a moon rover. “Astronauts who are familiar with geological exploration could operate the rover in real time, there’s much less delay [in the radio signals]. They could visit the oldest [known] impact basin in the solar system, and it would not require a human lander, would be cheap, and would give you the kind of experience that is going to be needed” for further exploration of the solar system.

The quest to populate the solar system would entail a search for signs of life – and for water and useful minerals, Burns says. “This is going to require knowledge of geology, chemistry, astronomy and mechanical engineering; it will be very different than the first few flights to the moon that were just trying to get there. I argue that the difference between manned and unmanned travel is going to start to fade.”

Historic moment

Tele-operation, as remote-control is currently called, is being used every day by earthbound “pilots” in Nevada to fly drones in the Middle East, highlighting the firm link between space engineering and the military.

Rockets and satellites have military roots, and the space race was an early and intense focus of Cold-War competition, as the United States and Soviet Union both relied on German rocketeers who had helped the Third Reich try to conquer Europe. Now the United States and Russia, World-War II allies, then Cold-War enemies, have become allies once again, at least in terms of space cooperation.

Dating back to the late 1950s, Smith says, “Space policy has always been as much about perception as reality. It goes all the way back to the first ballistic missiles, the space race, the missile gap.”

John F. Kennedy warned about a “missile gap” while running for president, and even though it proved illusory, the fear of Soviet supremacy — Sputnik was in orbit while American rockets were exploding in front of TV cameras — supported the development of missiles that could be used for global nuclear war or putting men on the moon.

The result was lavish budgets for rockets and space.

But the easy goals have been reached, and visiting the moon is so last-century. Visiting an asteroid will answer important scientific questions, but will never have the sex appeal of visiting the man on the moon. As Smith says, today, “We are in another gap; an ambition gap.”

David J. Tenenbaum