Discovery

A frequent commentary chronicling the creative and intellectual
excitement of discovery at Washington State University.

Brought to you by Washington State Magazine

Posts Tagged ‘planets’

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.

(more…)

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.

This Just In From Outer Space

This week’s American Astronomical Society meeting in Washington, D.C., is yielding a bonanza of discoveries light-year large and wavelength small.

For starters, the Hubble Space Telescope has found a slew of galaxies that nearly date back to the Big Bang.  Astronomers are forming an idea of how dark matter is distributed around the Milky Way—it’s like a squashed beach ball. And while scientists call CoRoT-7 b the first Earth-like planet outside our solar system, University of Washington astrobiologist Rory Barnes  reports it’s a 4,000-degree scorcher on sunny days.

Our own Guy Worthey, an associate professor of physics, is in attendance and writes of being particularly impressed by two discoveries, one well-publicized and another largely overlooked. His report:

One of the newsy things is the first five planet discoveries by the Kepler  mission (pictured, artist’s conception courtesy of NASA). They are all “hot jupiters” in the sense of being large planets that are very close to their parent star. And it pushes the number of known extrasolar planets well over the 400 mark. This should be the “tip of the iceberg” for the Kepler mission, which should give us good statistics on planets of many sizes, albeit ones that orbit stars that are, on average, quite far away.

One thing that personally impressed me is the work of Courtney McGahee and Richard Gray of Appalachian State University. They have investigated a rare class of chemically peculiar stars called Rho Puppis stars. The latest work on them was around 1978. The question is, why do these stars, only a half a dozen of which were known historically, have such odd spectra—their characteristic colors.

McGahee and Gray have definitively answered this question by finding several dozen more of them, getting high-quality spectra, and analyzing these spectra for their chemical fingerprint. The fingerprint looked very similar to the chemical pattern in a very numerous, very well-studied group of stars known as Am stars. These stars are very quiet in their surface “weather” and are able to “levitate” heavy elements like strontium, barium, and europium to the very top. So, even though they are stars of normal composition, the light that comes from the very surface looks like it has very large fractions of exotic heavy elements.

The final, and I think, definitive, answer from ASU is that the Rho Puppis stars used to be Am stars, but are in the process of cooling down and growing bigger. Rho Puppis stars are rare, because cool stars get stormier than the quiet Am stars, and when the storms get too violent, the gases will mix, and the odd chemical fingerprint will disappear. This change is a part of every star’s life. Our sun will do that in another 5 billion years.