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Archive for the ‘Space sciences’ Category

Plate tectonics key to life on Earth?

Tectonic plates. Courtesy US Geological Survey

Tectonic plates. Courtesy US Geological Survey

Is our vital blue planet the last of its kind?  Or has it always been one of a kind?  From the perspective of post-modern geologists, planet Earth is like no other solar body yet discovered.

“I think when you live on the Earth, you take it for granted,” says Katie Cooper, who thoughtfully considers such esoteric questions for a living. As one of a relatively new group of geologists who use computer simulations to study the thermal and tectonic evolution of our planet, her viewpoint is decidedly celestial.

Cooper, assistant professor in the School of Earth and Environmental Sciences, studies the broad area of geodynamics—particularly the evolution of Earth as a planetary system. Specifically, she models how the three main layers of our planet—core, mantle, and crust (lithosphere)—interact and change over time.

“I look at the Earth as a giant heat engine which drives all of the geologic activity we see at the surface,” she says. “In the past, the core was hotter than it is today. The planet is slowly cooling and that affects everything on the lithosphere.”

That cooling takes place in large part through thermal convection. Like boiling water or the slow movement of oil blobs in a lava lamp, hot plastic rock from the Earth’s mantle is constantly rising toward the surface, where heat and energy are released in hot springs, earthquakes, or volcanic eruptions. At the same time, cooler rock is sinking toward the interior core.

This steady interplay leads to the phenomenon of plate tectonics where vast puzzle-like sections of Earth’s crust “float” on top of hot rock in the mantle—and imperceptibly migrate across the globe.

Earth stands alone

Although plate tectonics is often taken for granted as standard planetary modus operandi, it turns out that Earth is a world apart from other planets.

“Plate tectonics is unique to Earth as far as we know right now,” says Cooper. “The big question is if this is unique to our solar system? Our galaxy?  The universe?”

Not only unique, but possibly essential to life itself. Through its part in cooling the planet’s interior, plate tectonics allows Earth to maintain a magnetic field that shields our world from dangerous solar radiation and, in effect, creates a safe haven for life to flourish. Which presents Cooper with another question—did plate tectonics create optimal conditions for the initial occurrence of life?  No one knows for sure.

Plate tectonics—the next generation

For the first half of the twentieth century, geologists suspected that Earth’s continents had once formed a single land mass before breaking up and drifting aimlessly apart. The continental drift hypothesis was backed up by fossil evidence but no one could explain the actual physical processes driving it.

That changed in 1963, however, when Princeton professor, Harry Hess, used WWII submarine-hunting technology to discover unusual magnetic polarity in the ocean floor. It was concluded that hot rock from the mantle was rising up through the lithosphere and pushing the sea floor—and the continents on either side—apart.

This finding provided the mechanism to explain the purposeful movement of Earth’s plates and led to the development of the first theory of plate tectonics.

Today Cooper is among a new generation of geologists who study what could be called “post” plate tectonics. Taking the field up a notch, she investigates similar processes on other planets and asks why Earth has plate tectonics in the first place.

“Is it the preferred mode of operation?” she asks. “Does it help the planet lose heat most efficiently? Is it a coincidence?”

Using a computer cluster of 600 processors working together as a single unit, Cooper attempts to unlock these mysteries by crunching enormous calculations that often run days or weeks to generate results.

Doing these “paper and pencil calculations” as she refers to them, Cooper builds computer models of planets and applies basic laws of physics to see if the theories are applicable.

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Next Stop, Neptune, If the Brakes Work

Next time you’re in a pub with a dart board, pick up a dart, stand at the regulation distance, and toss a bull’s eye. Piece of cake, right? Now, stand in that same pub but throw the dart so that it goes into a nice, near orbit around Neptune. Not so easy this time, eh?

But we’re not done. To make things a little trickier, figure on using Neptune’s atmosphere to brake your dart’s velocity. While you’re at it, calculate the path your dart took to get from the pub to Neptune. Write that path out in a series of differential equations. Write a 500-word abstract. Do all this is 48 hours under the auspices of your faculty mentor. You’re almost done! Last step: enter the paper you’ve just written in the University Physics Competition.

With slight variations on the process above (like, they didn’t actually throw a dart), that’s what three WSU physics majors did. Julian Smith, Kyle Welch and Ken Dorrance spent a recent weekend bravely battling the complexities of Lagrangian mechanics to calculate just what it would take to get a rocket from Earth to Neptune. Their efforts won them a bronze award in the competition.

Left to right: WSU Physics and Astronomy majors Kenneth Dorrance, Kyle Welch and Julian Smith/photo and montage by Brian Charles Clark

A couple centuries ago, mathematician Joseph-Louis Lagrange made significant contributions to celestial mechanics, the area of math that deals with the movements of planets, moons and various other objects in space – including rockets. “Newton’s second law–force equals mass times acceleration–beautifully describes many simple physical systems when forces are known,” says Dorrance, a junior majoring in physics with the nanotechnology option. “Lagrangian mechanics lets you solve some less-than-simple systems without knowing the forces.”

All three of the young physicists agreed that the mechanics involved in aerobraking a probe in the atmosphere of Neptune is a complex business. “Julian and I spent a lot of time staring at the white board, looking for analytical solutions, while Ken worked on coding methods for finding numerical solutions,” says Welch, a senior from Olympia majoring in physics and neuroscience.

“Being someone who focuses on theory, I often like to believe that there will be a clean analytical solution for everything,” says Welch. “However, the complexity introduced by the drag of aerobraking showed me that sometimes you have to give up on finding an exact solution.”

Not only was the problem complex, but the three-person team had only 48 hours in which to formulate their solution. This involved investigating the composition of the upper reaches of Neptune’s atmosphere where the probe would experience frictional resistance and be slowed enough from its interplanetary velocity to go into orbit around the gas giant. Between the three of them, they hammered out a solution that satisfied them.

The University Physics Competition annually offers teams a choice between two problems.

“We chose the problem we thought would be the most interesting, and opted out of the one we thought would be easier to solve,” says Smith a senior in physics from Vashon Island. “The aerobraking problem was exciting for all of us but we really had to think outside the box. This contest taught us to be creative and to think quick.”

Michael Allen, the students’ mentor and competition advisor, says the competition problems are unlike what they would find in a textbook.

“The problems do not have a single approach, and do not have a single correct answer,” he says. “Also, the students are allowed Internet access whilst solving the problem, hence they have a lot of information available to them and must pick that tiny, relevant bit of it to use. In other words, there is scope for being creative, but there is also a need for discipline.”

Science in the Sky: The WSU Planetarium

Note: This is the first in our new series, “Scene Around Campus: A Glimpse into WSU’s Corners and Curiosities.” Join us as we explore the many nooks and crannies of campus that residents and visitors might otherwise miss.

Welcome to “The Whoa Moment.”

You’re ushered into a room down a musty hallway. You take a seat, the lights go out, and — after a moment of darkness — the night sky flickers above you, a canopy of fuzzy white dots representing the universe as seen from Pullman. You forget about the world outside as you’re lost in space.

The Washington State University Planetarium is a 1960s star projector tucked away in Sloan Hall. WSU astronomers Michael Allen, Guy Worthey and Ana Dodgen lovingly keep it clean and in working order.

The planetarium is dated and clunky, but the astronomers’ faces light up when they talk about the roughly 2,000 fifth- and sixth-graders who visit every year on field trips.

“The little kids get so excited about what we’re telling them,” Dodgen says. “It’s a way to spark their curiosity in astronomy and science.”

Set up in 1962, the planetarium is likely older than these kids’ parents and possibly their grandparents. Working with the WSU Foundation, the astronomers are trying to collect donations to update the facility with a digital projector. Mostly, they’re hoping for a big donor, someone star-happy enough to hand over $50,000 or $70,000.

“Everyone loves the planetarium, but in terms of loving it enough to empty your wallet … that hasn’t happened yet,” Worthey says.

Within the planetarium, the projector is run from a main console with knobs for each celestial body. There are motors to animate daily, monthly and yearly paths. The console looks like a 1920s radio.

“This is like Frankenstein’s laboratory down here,” Worthey jokes during a recent visit, swinging Mars — a tiny red dot — across the screen.

Despite fuzziness and flickering, the northern hemisphere mostly works. From certain angles, pieces of the projector, a big black globe dotted with pinholes, block much of the rest of the sky. If you pick the wrong seat, the Southern Cross and Alpha Centauri might be obliterated.

The planetarium is closed to the public and used mainly for undergraduate science classes and local middle and elementary schools. However, WSU and community groups can schedule free shows through Allen or the physics department at astro.wsu.edu or 509-335-1279.

More News of Life on Mars and Saturn’s Titan

For several years now, WSU astrobiologist Dirk Schulze-Makuch has been building a case for extraterrestrial life. Just this spring, he and several colleagues reported finding microbial life in an incredibly inhospitable lake of asphalt in the Caribbean, suggesting life might similarly be found in the liquid hydrocarbon environments of Saturn’s moon, Titan.

Now comes word that ancient Mars seems to have had a wet, non-acidic environment favorable to life. Researchers led by NASA’s Richard Morris and writing in the journal Science say the evidence lies in an outcrop of rock with high amounts of carbonate, which forms in wet conditions and dissolves in acid.

Carbonate-Containing Martian Rocks (color added)/Image courtesy of NASA, JPL-Caltech, and Cornell University

The finding, says Schulze-Makuch, “supports the notion of a warmer and wetter early Mars with substantial amounts of liquid water on its surface, probably in the form of oceans. Thus, early Mars was certainly a habitable planet and the origin of single-cellular life on Mars or transfer of that type of life from Earth to Mars or vice versa is certainly plausible.”

No sooner does Schulze-Makuch say this when we read of the Cassini spacecraft finding no sign of acetylene on Titan. A separate study found evidence that hydrogen is disappearing near the moon’s surface. The discoveries support a theory that Titanic microbes could survive by breathing hydrogen gas and eating acetylene, producing methane as a result.

Schulze-Makuch calls the discoveries “extremely intriguing.”

“A biological explanation would be quite plausible as hydrogen is the most basic ingredient for metabolism on Earth and acetylene is an energy-rich molecule that could be harvested as part of a methanogenic metabolism on Titan,” he says.

In fact, he predicted as much in 2005, writing with David Grinspoon in the journal Astrobiology.

“Obviously, inorganic explanations have to be eliminated as a possibility before we conclude that biology is the cause,” he says. “However, an inorganic explanation is difficult to invoke since a strong catalyst would be needed to remove the hydrogen and acetylene falling from Titan’s atmosphere under the very cold surface temperatures on Titan. Indeed, what is observed is exactly what we would expect if life on Titan is present that uses hydrogen and acetylene in its metabolic pathway and produces methane as a result.”

Very cool video of how the Spirit Mars Rover operates on rock can be seen here. You can also read a lot more about Schulze-Makuch’s thinking on extraterrestrial life in his recent and eminently readable book, We Are Not Alone.