Scientific Method / Science & Exploration

Toxic gumbo

Katrina has come and gone, and now its clean-up time. Science.Ars looks at the …

Last week I wrote about the disastrous flooding of New Orleans. The repair efforts are now under way, but it's clear that parts of the area are going to be under water for many weeks—estimates for draining the city range into the months. But what kind of damage will continued exposure to the flood waters have?

Along with the water dumped in from Lake Pontchartrain comes the contents of underground storage tanks, the sewers, industrial chemicals and decomposing organic matter. The bottles of bleach and detergents that people kept beneath the kitchen sink. Paint from cans kept in the garage.  Worse still, all these different chemicals are mixing together in floodwater, reacting with each other, and breaking down with exposure to sunlight. Until the waters are drained and the sediment can be analyzed, there's no way to tell exactly what's been left behind or what exposure to the almost infinite combinations of pollutants that make up this toxic soup would result in.

Toxicologists have predicted that it's likely that residents might begin to develop ailments and symptoms similar to Gulf War syndrome. That condition is believed to stem from exposure to a range of chemical insults, from vaccinations and organophosphate exposure, along with other chemicals associated with the modern military in action.

Worse yet, as the waters drain from the bowl that is New Orleans, the surrounding region will suffer the same fate as the water returns to the Gulf of Mexico. On top of the yearly dead zones in the Gulf that are a result of agricultural runoff from the Mississippi River, the addition of this toxic sludge does not bear thinking about. Unfortunately for the coastal communities who made their living fishing the area, "Made in LA" is unlikely going to be a tempting draw at the local fishmonger. From Blinky the three-eyed fish to Troma, the drawbacks to a chemically-diverse environment have been commonplace in popular culture. Now we get to see what happens in real life.

Himalayan on the rocks

It's a funny old world. For some people, the problem is too much water. Others wish they were so lucky. For a while now, climatologists, environmentalists, meteorologists and other assorted weather wranglers have been looking at computer models of climate change, and have, by and large, come to similar conclusions. One of those things that pretty much every scientist agrees on is the potential for a severe water crisis in parts of the world.

Precipitation patterns are expected to shift, and rising temperatures mean that glaciers in the world's mountain ranges are shrinking. For those of us who live in Europe or North America, that might mean fewer weeks of being able to ski or snowboard, but the situation is slightly more worrying for anyone who depends on these alpine ice cubes for drinking water. Like, for example, the world's largest democracy, India. Regions of both India and China depend on Himalayan meltwater, and retreating glaciers are already causing water shortages in the highlands. With that corner of the world being the most densely populated and now among the fastest-developing, I wouldn’t be surprised to hear a lot more about the importance of fresh water in coming years.

Spread of the thinker?

Last week saw the publication of the chimpanzee genome, and with it, the opportunity to examine genetic basis for the difference between us and our closest relatives (subscription required). Comparative analysis of both genomes is revealing information about the way humans have evolved over several million years. This week, research published in Science takes a look at human evolution in action. Our greatest advantage over the rest of the planet is the human brain, and this work shows just how improvements to that organ work their way through the population.

The studies focus on two specific genes, microencephalin and ASPM, both of which cause primary microcephaly, a condition whereby the brain is severely stunted. By examining the frequency of difference variants, or haplotypes, of these genes in the population, the authors were able to see the effects of natural selection at work:

For each gene, they found an allele with a surprisingly high frequency in human populations. Statistical tests showed that these frequencies are unlikely to be due to random genetic drift or population migration, suggesting that the alleles were instead favored by natural selection. Making assumptions about past mutation rates, the team then estimated when each allele arose. The favored microcephalin allele clocked in at 37,000 years ago (with confidence intervals ranging from 14,000 to 60,000 years)—about the time of the explosion of symbolic behavior in Europe. The ASPM allele arose 5800 years ago (with a possible range of 500 to 14,100 years), just before cities arose in the Near East.

This is a fascinating development, although not without its own potential minefields. The distribution of a gene that would confer its owner with better cognitive powers than someone without it could have the potential to create a genetic underclass, and Dr. Lahn, head of the group behind the research, is cautioning people not to misinterpret this data:

Lahn warns that there is "a lot of potential for over- and misinterpretation" of his results. He points out that other advantageous alleles might have a very different population distribution. "You don't necessarily come out ahead" if you have these alleles, Lahn says: "We only picked out two."

Ancient solar systems

It's accepted wisdom that one day—hopefully far, far in the future—as it undergoes its eventual long and drawn-out death, the Sun will expand and envelope its closest planets, including our own home. As this event isn't predicted for 5 billion years, the odds of any human still being around to worry about it seem fairly remote. But would the death of a sun necessarily spell the end of that solar system?

New information from astronomers in Hawaii about a white dwarf called GD362 suggest a kind of geriatric period for solar systems;

These observations showed an unexpected excess of infrared in the light of the star, as well as a huge abundance of calcium – the second-highest ever seen from a white dwarf.

The calcium could only be explained by an influx of dust onto the white dwarf, and the infrared excess is best explained by a very thin, flat and highly opaque disc circling the star out to a radius of perhaps 1 million kilometers. The disc must be composed of dust that is continually being drawn onto the star's surface, producing its abundance of calcium, and other metals.

The thought of a calcium shell around a star, much like an eggshell, is certainly intriguing.

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