Category Archives: chemistry

atmosphere, atmospheric science, chemistry, NASA

The Hole at the South Pole

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The Ozone Hole

Earth's ozone hole, from data provided by NASA's Goddard Space Flight center and the Ozone Hole Watch. The blue area is the 'ozone hole', where the density of the ozone layer is at its thinnest this time of year.

One of the best things that NASA does (along with other space agencies) is give us a look at our own planet — as a planet.  That is, the scientists who study our world do so in the same way they would study any other planet. They chart changes on the surface, map atmospheric activity, and chart all those changes over time.  For the past decades, scientists have charted something called the ozone hole, which forms over the south pole of our planet each year.  This image shows what the ozone looks like as of September 13, 2010, courtesy of the OzoneWatch website.

Satellite instruments monitor the ozone layer, and scientists use the data to create the images that indicate the amount of ozone in the upper atmosphere. The blue and purple colors are where there is the least ozone, and the greens, yellows, and reds are where there is more ozone.  The depth and size of this Antarctic ozone hole are affected by the temperature of the stratosphere (the upper part of Earth’s atmosphere) and the amount of sunlight that bathes the south polar region.

So, why is ozone such an important thing to monitor? This is a useful gas for the protection of life on this planet.  In the upper atmosphere, ozone acts to absorb ultraviolet-B emissions.  Such emissions, which come primarily from the Sun, can harm living systems. It’s safe to say that, without the ozone layer in our upper atmosphere, life on Earth would be severely harmed.  In fact, without the ozone layer, it’s possible that life wouldn’t have formed on this planet.  So, losing a chunk of our ozone layer each year is a big deal.  Scientists want  understand why this happens.

Now the good news is that the ozone layer is not thinning anymore — after more than half a century of actively thinning.  This is due to a ban on harmful chemicals that have damaged the ozone  layer.

We know that ozone is destroyed by chlorine- and bromine-containing chemical compounds.  We know that some aircraft emissions hurt the ozone layer.  We know a lot of different reasons why our ozone layer is under attack, not just from the Sun, but from below by the sentient life forms that inhabit the planet.

Sure, there are naturally occurring attacks on the ozone, but the largest attack comes from human activity. We use huge amounts of chemical compounds in industrial and home-based products. You may have heard of what’s referred to as chlorofluorocarbons. They escape to the atmosphere from refrigeration and propellants.  They persist for years in the lower part of the atmosphere, and eventually some migrate to the upper atmosphere. It’s a long-term process because the destruction of ozone doesn’t happen the minute CFCs get into the atmosphere.  But, it does eventually happen. So, even though we HAVE reduced our use of these compounds — the damage from the reservoir of ozone-destroying atoms and molecules has continued.  The damage that now shows up in the ozone hole probably comes from materials released well into the last century. With luck, and the continued ban on these chemicals, the ozone should get back to its 1980 levels by mid-21st century.

I know that there are still people who deny such problems existed — generally they are people who don’t want to believe that humans can have a deleterious effect on our planet’s ecosystems. The problems won’t go away because some people bury their heads in the sand. Oh, sure, their faces won’t get sunburned by the UV-B, but their hineys will.

So, what’s the effect of the loss ozone? Ask the people who live under that hole and who are at higher risk for cancer and other conditions that are caused or exacerbated by exposure to ultraviolet-B.  I was in South America a few years ago, at the very tip of the continent. The people who live there know first-hand what it’s like to live under a thinning ozone layer.  Sunblock is a constant friend.  Children are warned NOT to go out with out adequate clothing and sunblock.  If you want to know what life would be like on this planet with a thinner (or nearly nonexistent) ozone layer, talk to the children of Patagonia.

And, thanks to NASA and other agencies who continually monitor our planet from space (another fine example of how space exploration benefits us here at home), we might be able to learn enough to avoid dissipating our ozone layer more than it already is.

astronomy, chemistry, comet dust, cosmic chemistry

Before the Beginning

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Comets As Probes of Pre-solar System History

When comets do a turn around the Sun, they leave behind streams of dust particles that Earth eventually intersects in its own orbit around the Sun. Most of the time we see these particles as they enter our atmosphere and burn up. It’s rare to get samples of these dusty bits, but when planetary scientists DO get them, they’ve basically gotten their hands on very old, very primitive bits of material that existed LONG before the Sun and planets did. This is because comets formed out of the materials in the protosolar nebula — essentially they’re orbiting deep-freezes of ice and dust.  Scientists have long known about comets and their treasure troves of ancient stuff.  In 2003, they managed to gather up good samples of Comet 26P/Grigg-Skjellerup and have been studying them since then.

Interplanetary dust particles showing pre-solar grains of silicates and organic matter that originated in interstellar space. Courtesy H. Busemann. Click to embiggenate.
Interplanetary dust particles showing pre-solar grains of silicates and organic matter that originated in interstellar space. Courtesy H. Busemann. (Click to embiggenate.)

The findings are amazing. According to Dr. Henner Busemann of the University of Manchester, who is presenting these results on Tuesday at the European Week of Astronomy and Space Science being held at University of Hertfordshire in the U.K., the dust grains have all the signs of being very ancient — predating the birth of the Sun and planets. Some of it is true stardust, floating in interstellar space after being ejected during the process of birth, life and death of other stars. “We found an extraordinary wealth of primitive chemical fingerprints,” he said, “including abundant pre-solar grains, true stardust that has formed around other earlier stars, some during supernova explosions, associated with extremely pristine organic matter that must pre-date the formation of our planets.”

You can see a sample of the dust particles here. They are extremely tiny — only a few thousands of a millimeter in diameter.   Two grains appear to have materials that scientists predict match the solar system’s birth nebula. One dust particle contained four pre-solar silicate grains (meaning grains that existed well before the solar system’s birth nebula formed) with an unusual chemical composition that matches the kinds of silicate grains that might form in supernova explosions. This is pretty good evidence that our birth nebula was seeded by the death throes of older, massive stars that once existed near our part of the galaxy.

More closeups of comet dust grains from the pre-solar-system neighborhood, more than 4.5 billion years ago. (Click to embiggenate.)
More closeups of comet dust grains from the pre-solar-system neighborhood, more than 4.5 billion years ago. (Click to embiggenate.)

One of these grains is a fragment of olivine and was found next to a hollow globule of carbon, most likely of interstellar origin. Carbon is an interesting element to find because it is intimately bound up in the structures that ultimately build life.

Organic coatings are suspected to be the shells of time capsules that protected and secured the survival of some of these fragile stellar silicate grains as they made their way through the interstellar environment and, later on, the high radiation environment of the newly forming Sun.

Detecting the Chemistry of Life

This isn’t the only big news coming from the WASS meeting.  Two researchers are also presenting a paper about the detection of two of the most complex molecules yet discovered in interstellar space: ethyl formate and n-propyl cyanide. Their computational models of interstellar chemistry also indicate that yet larger organic molecules may be present — including the so-far elusive amino acids, which are essential for life. The scientists used the IRAM 30-meter telescope in Spain to look at a region of the sky near the star-forming region Sagittarius B2.  The molecules were found in a hot, dense cloud of gas that also contains a newly formed star.

Large, organic molecules of many different sorts have been detected in this cloud in the past, including alcohols, aldehydes, and acids. The new molecules ethyl formate (C2H5OCHO) and n-propyl cyanide (C3H7CN) represent two different classes of molecule — esters and alkyl cyanides — and they are the most complex of their kind yet detected in interstellar space.

This is pretty cool news on both fronts. These findings by separate groups of scientists tell us that we (our planet and our star) came from some of the same processes we see happening throughout the galaxy.  The precursors of life are out there floating around in interstellar space, and scientists are finding more and more of them. It’s one thing to know and suspect these facts, but quite exciting to find evidence of our origins as part of the normal evolution of the universe and its stars and galaxies.