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Archive for April, 2010

Twisted

The National Science Foundation and the National Oceanic and Atmospheric Administration are contributing over $10 million for an ambitious study of tornadoes across the central United States this summer. The funds will pay for a team of over 100 scientists from seven countries, as well as a fleet of mobile labs and equipment that will trek across more than 900 miles of American heartland during the height of tornado season.

Tornadoes (or twisters) are among the most violent atmospheric disturbances on Earth. They are rotating columns of air, simultaneously maintaining contact with the ground and a cloud overhead. While most observed tornadoes are mild or moderate in wind speed and size, the most violent can have wind speeds of over 300 miles per hour, stretch over a mile wide, and travel dozens of miles over land, leaving a trail of complete destruction.

A tornado near Anadarko, Oklahoma on 3 May 1999. Image provided courtesy of the National Oceanic and Atmospheric Administration and Daphne Zaras.
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The California Geological Survey turns 150 this year. As part of that celebration, they have released new maps revealing the state’s complex geology. One map in particular is making headlines: a map of all the known fault lines in California, including those discovered since the last fault map was put together in 1994. This fault activity map color codes fault lines based on their most recent activity. For the record, the faults in red and orange are the most active cracks to fret over.

In geology, a “fault” can refer to almost any break in a chunk of rock, as long as movement or displacement periodically occurs along that fracture. The many tectonic plates that make up Earth’s surface (go here to learn more) move past one another and collide along zones of complex fault lines, where the slow movement of the plates has caused fracturing of rock on both sides of the boundary. California is a textbook example of such a zone of fault lines. While most of the state resides on the massive North American Plate, a significant chunk (including all of coastal California south of the Bay Area) actually resides on the equally massive Pacific Plate. At California, the North American and Pacific plates are sliding past one another. The North American plate is moving south and east relative to the Pacific Plate’s north and west course. This plate boundary also extends further south, where past movements have torn lower California (the Mexican states of Baja California and Baja California Sur) away from the mainland, opening up the Gulf of California. However, plate boundary is at its most geologically troublesome as it runs through the American State of California.

The Pacific plate is on the left, while the North American plate is on the right. Image provided courtesy of the United States Geological Survey.
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Oceans from Above

Two independent reports published in this week’s issue of the journal Nature report the existence of ice in a rather unexpected place: an asteroid. The asteroid in question is 24 Themis, a rather large resident of the Asteroid Belt. This discovery may leave you wondering, “Who cares?” Well, the implications of this finding have a lot to do with us, and one of the substances that was absolutely required for life to evolve and thrive on this planet: water.

Let’s start answering the “Who cares?” question by defining some fancy terms. An asteroid is a small, rocky or metallic body that orbits the sun. They’re smaller than planets and dwarf planets, but larger than the largest (boulder-sized) meteoroids. 24 Themis was discovered in 1853 and has a diameter of about 123 miles. As for the Asteroid Belt itself, this region lies between the orbits of Mars and Jupiter. As the name suggests, it is a “belt” of asteroids and smaller meteoroids, all orbiting the sun. Asteroid belt residents range in size from collections of space dust to the dwarf planet Ceres.

Two teams independently looked at 24 Themis in the Asteroid Belt using NASA’s Infrared Telescope Facility atop the Mauna Kea volcano in Hawaii. The teams looked at how sunlight is reflected off of 24 Themis’ surface. Different wavelengths of light can be absorbed, reflected, or scattered based on the chemical properties of substances that the light hits. In the case of 24 Themis, both teams found that light hitting the asteroid’s surface was scattered in a pattern consistent with the presence of a very familiar chemical: water. In this case, both teams conclude that there is a thin layer of frost on the surface of 24 Themis.
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The threespine stickleback made a brief appearance in yesterday’s New York Times. I pay attention to such things (albeit one day late) because I study threespine sticklebacks and their close relatives for my thesis research on the evolution of sex chromosomes.

However, the stickleback’s appearance yesterday had nothing to do with my research. But, a team from the University of Bonn, led by Marion Mehlis, looked at the threespine stickleback to address a very specific question: cannibalism. Many animals, for one reason or another, eat their young. Sticklebacks are no exception. Male sticklebacks guard nests of fertilized eggs during the breeding season (female sticklebacks play no part in parenting). But, sometimes, a male will eat some or all of the eggs in his nest. Why? What triggers this behavior?

It certainly seems counterproductive. Male sticklebacks do all the work in the breeding season: defending a territory, building a nest, courting female after female, chasing a female away once she lays her eggs in the nest, fertilizing the nest, and caring for the eggs until they hatch. Why would any male in his right mind go to all the effort of building a nest a courting a female when he’s just going to devour his kids before they hatch? Well, as it turns out, he might do that when those aren’t his kids in the nest.

In the stickleback field (as in other fields), there is another group of males — the sneaker males. These males don’t typically build nests and defend territories. They lurk near a courting couple, waiting until a female has laid her eggs in another male’s nest. Then, the sneaker male enters the nest (usually while the hard-working male is busy chasing away the female) and fertilizes the eggs. Sneaker male (now sneaker dad) swims away, leaving the hapless hard-working male to tend his offspring.

Mehlis and colleagues wondered: do stickleback males eat the eggs in their nest when those eggs were fertilized by another male? They conducted trials to test this, switching batches of eggs (we call them “clutches”) in a nest tended by one male with eggs that were fertilized by another male. As it turns out, a male stickleback is much more likely to consume eggs if those eggs weren’t fertilized by him — if he wasn’t the dad. Mehlis and colleagues aren’t exactly sure what kind of signal the male is sensing that indicates paternity, but it’s likely some sort of olfactory (“smell”) cue.

The study sheds some light on the puzzle of male stickleback cannibalism. As for the type of signal at work in these fish, stay tuned!

Image of female (upper) and male (lower) threespine sticklebacks provided courtesy of Dr. Joseph Ross.

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This true-color image shows southwestern Australia as it appeared on 18 August 2002. A significant chunk of the coastal region is green, a sign that ample seasonal rainfall has done its job. However, to the north and east, hot and dry conditions persist, as a reminder that much of the Australian landscape is dominated by the arid and semi-arid “Outback.”

Australia is the driest inhabited continent, and it is getting drier. The patches of temperate and sub-tropical areas along the coast (including the pictured bit of southwestern Australia) are getting warmer, but receiving less rainfall. Much of southeast Australia (including most of the major urban centers) has been wracked by a decades-long drought. The Murray-Darling river system in the southeast, the only major river system on the continent, is drying up quickly, depriving the country’s limited agricultural land of much-needed irrigation. Cities like Western Australia’s Perth (with a 2009 population of 1,659,000) have seen water demand spike as reservoirs drop. Already, the country has three desalination plants operating to provide water for coastal cities, with three more under construction and at least one more planned. These desalination plants will likely increase Australia’s greenhouse gas emissions, already the highest per capita in the world.
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South to the Future

Today, the European Southern Observatory (ESO) announced plans to build the world’s largest telescope in northern Chile. The ESO is an intergovernmental partnership of fourteen European nations1 to build and maintain Earth-based celestial observatories. Initially founded in 1962 by just five countries, the organization currently maintains three widely successful observatories below the equator — all in Chile’s Atacama Desert.

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NASA has some new breathtaking images available from the Hubble Space Telescope’s 20 year legacy of exploration. Since a picture speaks a thousand words, I’ll say no more. Go look at the images for yourself!

Image of the Carina Nebula courtesy of NASA, the European Space Agency, M. Livio, and the Hubble 20th Anniversary Team.

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