Our Window on Nature

These may be the longest nights of the year, but as seen from space the world is covered with lights. And that makes stargazing and watching meteor showers more difficult.

Tonight is the middle of the three day meteor shower called the Ursids. It’s not one of the brightest, but still there may be as many as 15 meteors streaking across the sky each hour.

These fragments came from Comet Tuttle, although their name comes from their apparent direction - the constellation Ursa Minor, better known as the Little Dipper. Don’t worry about looking in any exact location, but generally face towards the North.

Although this is a minor meteor shower, the conditions will be good this year since the moon won’t get in your way. But it will be more important than usual to get away from the city lights. The best viewing time may be during the hour before dawn. Get up a little early and wear your warmest coat.

The Winter Solstice is almost upon us (at least in the Northern Hemisphere), and according to many that brings on the first day of Winter. I wonder if we should tell that to all those digging out from this year’s early snowstorms. But December 22nd does, at least, have the longest night and the shortest day.

Because the axis of the earth is tilted, as we make our yearly journey around the sun different parts of the earth receive increasing or decreasing amounts of sunlight. And the amount of sunlight, of course, affects the temperature. But as with most things in nature, it’s not quite as simple as it sounds.

If you heat a pot of water on a stove, turning off the burner doesn’t immediately bring the liquid back to room temperature. In the same manner, after the oceans and landmasses have been heated during the summer, the warming effects don’t disappear as soon as the days start becoming shorter.

Of course the same is true in reverse, and it will be a while before we see the first signs of a new season. But the solstice is the turning point, both in the gradual change in the angle of the sun’s rays, and in the number of hours we can spend outdoors watching things like the changing seasons.

NASA released several photos today showing the possibility of water on Mars. They didn’t actually find the water, but by comparing photographs taken in August 1999 with the same location in September 2005, there is exciting news. The new picture shows a major change that occurred some time in the last five to seven years. According to the NASA website

The atmosphere on Mars is so thin that liquid water cannot persist at the surface. However, researchers propose that water could remain liquid long enough, after breaking out from an underground source, to carry debris before totally evaporating and freezing.

The photo at the left shows the before and after pictures, and scientists believe the several hundred foot long white streak was caused by flowing water. If this is the case, it increases the possibility of finding microbial life on Mars.

Watching the night sky can be fascinating any time of year, but during meteor showers it takes on the characteristics of a fireworks show. But just what is the object that causes all the excitement?

Let’s start with the name, because it changes depending on where you find it. While they are still out in space they are called meteoroids. As they flash though the sky on their way to the earth they are called meteors. And if they don’t burn up in the atmosphere, when they reach the ground their name changes to meteorites.

Some meteors are made up of a stony substance, mostly silicate materials. Others may be an iron-nickel combination. Or perhaps it is a blend of the two. But this is material from outer space that intersects our path as the earth travels around the sun.

A few people collect meteorites as a hobby while others do it for the sake of science. The problem with meteorites, unless you just buy them on EBay, is to find them. To be successful you either need a lot of luck or must understand why certain locations are better than others.

Meteorites deteriorate just like other rocks and minerals on earth, but in very dry areas this process can take millennia. So when scientists want to search for these space visitors, they usually head toward the South Pole.

At first thought this might seem a strange place to look for a dry climate, but the pictures of ice that come to mind ignore the fact that the Antarctic is classified as a desert because of the lack of moisture – an almost complete lack of liquid water. This means that rocks, or in this case the meteorites, will resist deterioration for a very long time.

The average age of a meteorite found in Antarctica is about 4.5 billion years, and scientist say that most of these discoveries have been on the earth for between 25,000 and 65,000 years.

Since 1976 the Antarctic Search for Meteorites (ANSMET) has sent 20 search teams to Antarctica, collecting over 10,000 meteorites. A combination of wind conditions and shrinking ice packs provide concentrations of these space fragments found nowhere else.

There is a real advantage to looking for meteorites on an ice pack. In most areas of the world these hunks of rock can easily disappear – buried in the ground, behind a bush, or hidden deep in a forest. But on an ice pack, there is almost no place to hide. Add to this the contrast between a black piece of rock and a white background, and an ice field becomes the perfect area to search.

Most meteorites come from debris caused by collisions of larger bodies in the asteroid belt, but some are actually from the moon or from Mars, blasted into space by a grazing blow from another space visitor. Those from the moon were identified by comparing them with rocks collected by astronauts, while fragments from Mars were determined when the gasses held inside their bodies matched those collected by robotic travelers to the red planet.

If you can’t afford the time for a quick trip to McMurdo Station in Antarctica, you can join them vicariously on the ANSMET website at http://geology.cwru.edu/~ansmet/index.html. Lots of pictures and a great explanation of what they do.

Tonight and over the weekend may be a great time for meteor watchers. It’s the middle of the Leonid Meteor shower, and this year the show could be more impressive than usual.

As a comet travels in its circular path, it drops off small particles which, over centuries, may eventually trail through the comet’s entire orbit. When the earth intersects this path you have a meteor shower. We pass through the orbit of the comet Tempel-Tuttle every November.

The picture on the left is of a Leonid fireball, taken from a DC-8 during the 2002 meteor shower. You can’t get quite that good a view from the ground, but some years meteor shows are truly impressive.

There’s almost no moon this weekend, so there won’t be much visual competition. If you can get completely away from city lights you can see twice as many meteors. The best times should be just before midnight. Just remember — dress warm.